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PNCMI 2012

Polarized Neutrons for Condensed Matter Investigations

Paris July 2-5th 2012

FIAP Jean Monnet, salle Bruxelles, Paris

Chair

A. Gukasov (Laboratoire Léon Brillouin)

Scientific committee

C. Alba-Simionesco (LLB, chair) M. Arai (J-parc) D. Argyriou (ESS) G. Badurek (Univ. Vienna) A. Belushkin (JINR) P. Böni (TUM) J. Campo (Univ. Zaragoza) R. Dagleish (ISIS) B. Farago (ILL) J. Fernandez-Baca (ORNL) J. S. Gardner (NIST)

S.V. Grigoriev (PNPI) K. Habicht (HZB) A. Ioffe (JCNS) K. Kakurai (JAEA) T. Keller (TUM) G. McIntyre (ANSTO) K. Pappas (TU Delft) B. Rössli (PSI) L.P. Regnault (CEA) H.M. Shimizu (KEK)

Local organizing committee (Laboratoire Léon Brillouin)

P. Bourges C. Doira B. Gillon S. Klimko S. Longeville

B. Mailleret I. Mirebeau F. Ott C. Rousse

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PNCMI 2012 Program

Monday, July 2nd 2012

Session: Geometrical frustration, Chair: I. Mirebeau

9:00 Opening

9:10 Steve Bramwell, Magnetricity and Magnetic Monopoles in Spin ice, University College London.

9:45 Pascale Deen, Disorder in the Laves phase compound ZrMn2, European Spallation Source, Lund, Sweden.

10:05 Shigeki Onoda, Higgs transition from magnetic Coulomb liquid to ferromagnet in Yb2Ti2O7, Condensed Matter Theory Laboratory, RIKEN, Japan.

10:35 Lieh-Jeng Chang, Polarized neutron studies on the Higgs transition in the quantum spin ice Yb2Ti2O7,

National Cheng Kung University, Taiwan.

10:55 coffee break

Session: Frustration and Chirality Chair: I. Mirebeau

11:15 Virginie Simonet, Chirality in Fe-langasite, Institut Néel, CNRS & UJF, Grenoble, France.

11:45 Sergey Grigoriev, The hexagonal spin structure of A-phase in MnSi, Petersburg Nuclear Physics Institute, Gatchina, Saint-Petersburg, Russia.

12:05 Dieter Lott, Chirality effects in Rare-Earth Multilayers investigated by polarized neutrons, Helmholtz Zentrum Geesthacht, Germany.

12:35 Jonas Kindervater, Spherical neutron polarimetry with MiniMuPAD: Investigations of the transition from heli- to paramagnetism in MnSi, Technische Universität München, Germany.

12:50 Robert Georgii, Polarised neutron scattering from skyrmions, Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universität München, Germany.

13:10 – 14:30 Lunch

Session: Multiferroics and chirality, Chair: J. Rodriguez-Carvajal

14:30 Markus Braden, Polarised neutron-scattering investigations on chiral multiferroics, Universität zu Köln, Germany.

15:00 Laurent Chapon, Electric field control of the magnetic chiralities in ferroaxial multiferroic RbFe(MoO4)2, Institut Laue Langevin, Grenoble, France.

15:30 Kirill Nemkovski, Resonance mode in rare-earth systems with valence instability, Forschungszentrum Jülich, Jülich Centre for Neutron Science, Outstation FRM II, Germany.

15:50 Catherine Pappas, From Liquid Crystals to Chiral Magnets, Delft University of Technology, the Netherlands

16:10 Sylvain Petit, Spin dynamics in multiferroic RMnO3, Laboratoire Léon Brillouin CEA/CNRS, Saclay, France

16:40 – 19:00 POSTER SESSION A and coffee break

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Tuesday, July 3rd 2012

Session: Strongly correlated electron systems and polarisation, Chair: Ph. Bourges

9:00 Mun K. Chan, Novel Magnetism in the Pseudogap Phase of the Cuprates, University of Minnesota, USA.

9:30 Balint Náfrádi, Structural and Antiferromagnetic Domains in Undoped YBa2Cu3O6, Ecole Polytechnique Federlae de Lausanne, Switzerland.

9:50 Andrew Boothroyd, Spin anisotropy of the resonance peak in unconventional superconductors, University of Oxford, United Kingdom.

10:20 Meng Wang, Antiferromagnetic order and superlattice structure in nonsuperconducting and superconducting RbyFe1.6+xSe2, Chinese Academy of Sciences, Beijing, China.

10:40 Emilio Lorenzo, Spin-Peierls phase transition in CuGeO3 revisited in the light of polarized neutron scattering experiments, Institut Néel, CNRS et Université Joseph Fourier, Grenoble, France.

11:00 coffee break

Session: Strongly correlated electron systems and polarisation, Chair: G. Chaboussant

11:20 Frédéric Bourdarot, Polarized Neutron on URu2Si2, CEA & Univ. Joseph Fourier, Grenoble, France.

11:40 Louis-Pierre Regnault, Temperature dependence of magnon lifetimes in the quasi-2D collinear S=1 honeycomb-lattice antiferromagnet BaNi2(PO4)2, CEA & Univ. Joseph Fourier, Grenoble, France.

12:00 Markos Skoulatos, Magnetism and orbital physics of the Mott insulator LuVO3, Paul Scherrer Institut, Villigen, Switzerland.

12:20 Vladimir Voronin, Measurement of neutron electric charge by the spin interferometry technique Petersburg Nuclear Physics Institute, Gatchina, Russia.

12:40 Vladimir Kozhevnikov, Magnetic field profile and microscopic parameters of nonlocal superconductors, Tulsa Community College, Tulsa, OK, USA.

13:00 – 14:20 LUNCH

Session: Imaging, Chair: F. Ott

14:20 Nikolai Kardjilov, invited, Imaging of magnetic structures with polarised neutrons, Helmholtz Centre Berlin for Materials and Energy, Germany.

15:00 Takenao Shinohara, Development of quantitative magnetic field imaging using time-of-flight neutron polarization analysis, J-PARC Center, Japan Atomic Energy Agency, Japan.

15:20 Wolfgang Treimer, Imaging Quantum Mechanical Effects in Superconductors with Polarized Neutrons, Helmholtz Centre Berlin for Materials and Energy, Germany.

15:40 Markus Strobl, Multiple potential of TOF spin-echo induced spatial beam modulation (SEMSANS), European Spallation Source, Lund, Sweden.

16:00 coffee break

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Tuesday, July 3rd 2012

Session: Facilities News, Chair: A. Gukasov

16:20 Alain Menelle, The CAP 2015 program at the Laboratoire Léon Brillouin, Laboratoire Léon Brillouin CEA/CNRS, Saclay, France.

16:35 Masahiro Hino, Design of VIN ROSE at BL06 beam line in J-PARC/MLF, Research Reactor Institute, Kyoto University, Kumatori, Osaka, Japan.

16:50 Thomas Krist, Polarizing neutron optics from Helmholtz-Zentrum Berlin, Helmholtz-Zentrum Berlin for Materials and Energy, Germany.

17:05 Klaus Habicht, New polarised neutron opportunities at the upgraded three-axis spectrometer FLEXX, Helmholtz-Zentrum Berlin für Materialien und Energie, Germany.

17:20 Takeda Masayasu, A New Polarized Neutron Reflectometer (SHARAKU) at the Intense Pulsed Neutron Source of the Materials and Life Science Experimental Facility of J-PARC, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Japan.

17:35 Garry McIntyre, Up-Coming Polarised Neutron Capabilities on ANSTO Instruments Using Polarised 3He Neutron Spin Filters, Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia.

17:50 Xin Tong, Current status of the polarized 3He R&D work at SNS, Oak Ridge National Laboratory, USA.

18:05 Takayuki Oku, Current status of polarized neutron related activity of J-PARC, JAEA J-Parc Center, JAEA.

18:20 End of the session

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Wednesday, July 4th 2012

Session: Thin films and nanomagnets, Chair: B. Gillon

9:00 Fernando Palacio, Spin Densities in Molecule-Based Magnets: Understanding Magnetic Interaction Mechanisms, Material Science Institute of Aragón, CSIC-University of Zaragoza, Spain.

9:35 Maxime Deutsch, Joint charge and spin densities refinement, Institut Jean Barriol, Univ.de Lorraine, France.

9:55 Dominique Luneau, Polarized Neutron Diffraction and molecular magnetic anisotropy: The local susceptibility tensor approach, Université de Lyon, France. 10h15 Oksana Zaharko, Source of magnetic anisotropy in a soft layered magnet WCuT, Laboratory for Neutron Scattering, Paul Scherrer Institute, Switzerland.

10:35 Erwin Jericha, USANSPOL studies of the microstructure of magnetic ribbons, Vienna University of Technology, Atominstitut, Austria.

11:55 coffee break

11:15 Andreas Michels, Magnetic neutron scattering on nanomagnets: Decrypting cross-section images using micromagnetic simulations, Laboratory for the Physics of Advanced Materials University of Luxembourg.

11:50 Kathryn Krycka, Disrupting Interparticle Magnetic Cross-Talk within Fe3O4 Nanocubes Using FePt Inclusions, NIST Center for Neutron Research, Gaithersburg, USA.

12:10 Valeria Lauter, Controlled interfaces for novel physical phenomena and functionality: Interface-induced ferromagnetism at paramagnetic/antiferromagnetic perovskite films, Oak Ridge National Laboratory, USA.

12:30 Yuri Nikitenko, Magnetic layer in a neutron wave resonator.

12:45 Kirill Zhernenkov, RF field stimulated magnetization kinetics probed in thin films with MIEZE based Time-Resolved AC(TRAC)PNR, Ruhr University Bochum, Germany.

13:00 Lunch

Session: Soft Matter, Chair: S. Longeville

14:20 Michihiro Nagao, Neutron spin echo revealed thickness fluctuations in surfactant membranes Center for Exploration of Energy and Matter, Indiana University and NIST Center for Neutron Research, USA.

15:00 Jin Kui Zhao, Polarized neutron in structural biology – present and future outlook, NIS-Division, Oak Ridge National Laboratory, USA.

15:20 Yohei Noda, Spin contrast Variation Study of fuel-efficient tire rubber, Japan Atomic Energy Agency, Japan.

15:40 Earl Babcock, Polarization Analysis using 3He for incoherent background reduction in SANS, Forschungszentrum Jülich, Jülich Centre for Neutron Science, Outstation FRM II, Germany.

16:00 Florian Piegsa, Dynamically Polarised Proton Spins as a Tool to Tune the Scattering Cross Section in Neutron Laue Diffraction, ETH Zürich, Switzerland.

16:20 Poster session B and coffee break

19:00 end of the session

19:30 Conference dinner, cruise on the Seine

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Thursday, July 5th 2012

Session: Instrumentation and methods - polarised neutrons, Chair : A. Menelle 09:00 Werner Schweika, Towards TOF spectroscopy and Laue diffraction with spherical polarimetry, Forschungszentrum Jülich, Jülich Centre for Neutron Science, Outstation FRM II, Germany.

09:20 F. William Hersman, Polarized 3He production exceeding 100 liters per day using Spin Exchange Optical Pumping, University of New Hampshire, Durham, USA.

09:35 Jeroen Plomp, Demonstration of spatial intensity modulated TOF SESANS with simple tools, Delft University of Technology, The Netherlands.

09:50 Thomas Keller, Frontiers of Neutron Larmor Diffraction, Max-Planck-Institut für Festkörperphysik, Stuttgart, Germany.

10:10 Tatsuro Oda, A beam divergence correction for NRSE spectrometer using polygonal 2D-focusing supermirrors, Kyoto University, Japan.

10:25 Felix Groitl, Larmor labeling methods: Neutron Resonance Spin Echo spectroscopy beyond standard line width measurements, Helmholtz-Zentrum Berlin für Materialien und Energie, Germany.

10:40 Alexander Ioffe, Latest developments of polarized neutron scattering instrumentation at the JCNS, Forschungszentrum Jülich, Jülich Centre for Neutron Science, Outstation FRM II, Germany.

10:55 Coffee break

11:20 Stephan Mattauch, MARIA – The high-intensity polarized neutron reflectometer of JCNS, Jülich Centre for Neutron Science (JCNS), Garching, Germany.

11:35 Wolfgang Haeussler, Studying slow dynamics and depolarizing systems with NRSE-MIEZE at the ESS, FRM II, Garching, Germany.

11:50 Wang Chun Chen, A Polarized 3He Neutron Spin Analyzer for SANS Polarization Analysis, National Institute of Standards and Technology, Gaithersburg, Maryland.

12:05 Patrick Hautle, Neutron spin filtering with dynamically polarized protons using photo-excited triplet states, Paul Scherrer Institute, Villigen, Switzerland.

12:20 Thomas Gentile, Wide Angle Polarization Analysis with Polarized 3He Neutron Spin Filters, Stop 8461, NIST, 100 Bureau Drive, Gaithersburg, Maryland USA.

12:35 Sergey Kozhevnikov, Polarizing Fe-Co-Fe planar waveguide for neutron microbeam production, Frank Laboratory of Neutron Physics, JINR, Dubna, Russia

12:50 closing remarks

13:00 End of the conference

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Poster Session Programme

Poster Session A, Monday, July 2nd 2012 A01 E.Moskvin, N.Potapova, V.Dyadkin, C.Dewhurst, S.Siegfried, D.Menzel, S.Grigoriev, Quantum criticality in Mn1-xFexSi studied by SAPNS A02 N. Martin, L.-P. Regnault, S. Klimko, K. Zhernenkov, D. Gorkov, B.P. Toperverg, Neutron Resonant Spin-Echo techniques using ZETA option on thermal TAS IN22 – Beyond inelastic spectroscopy A03 T. J Hicks, A. Mulders, C. Pappas, The Magnetic Defect in Antiferromagnetic Gamma Manganese Copper A04 S.V. Grigoriev, N.M. Potapova, E.V. Moskvin, V.A. Dyadkin, Ch. Dewhurst, S.V. Maleyev, Evolution of spin structure in MnSi close to TC under magnetic field A05 Fatih Zighem, Frédéric Ott, Numerical calculation of magnetic form factors of complex shaped nano-particles coupled with micro-magnetic simulations A06 E.V.Velichko, Yu.O.Chetverikov, L.A.Akselrod, V.N.Zabenkin, V.V.Piyado, A.A.Sumbatyan, W.H.Kraan, S.V.Grigoriev, The new calibration technique for SESANS-device. A07 S. Disch, E. Wetterskog, R. P. Hermann, A. Wiedenmann, G. Salazar-Alvarez, L. Bergström, Th. Brückel, Shape-induced superstructure in concentrated ferrofluids A08 Chin Shan Lue, L. J. Chang, M. Takeda, C. H. Lee, G. Chern, Magnetic anisotropy in the interface of Fe3O4/Mn3O4 superlattices probed by neutron reflectivity A09 S. M. Amir, M. Gupta, A. Gupta, M. Horisberger and J. Stahn, Effect of Sn surfactant in Fe/Si multilayers probed by neutron reflectivity A10 V. Tarnavich, D. Lott, S. Mattauch, S.Grigoriev, Study of induced chirality in Ho/Y myltilayers A11 Yohei Noda, Daisuke Yamaguchi, Putra Ananda, Satoshi Koizumi, Yoshifumi Sakaguchi, Takayuki Oku, and Jun-Ichi Suzuki, Polarization Analysis Equipment in SANS-J-II : Study of Polymer Electrolyte Membrane for Fuel Cell. (78bis) A12 Christine Klauser, Thierry Bigault, Jérémie Chastagnier, David Jullien, Pascal Mouveau, Alexandr Petoukhov, Natalyia Rebrova, Torsten Soldner, High Precision Depolarization Measurements in Polarizing Supermirrors A13 P. Schmakat, M. Schulz, V. Hutanu, M. Brando, C. Geibel, M. Deppe, C. Pfleiderer, P. Böni, Magnetic anisotropy of the Kondo lattice system CePd1-xRhx

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A14 Ikram DHOUIB, Zakaria ELAOUD, Philippe GUIONNEAU, Stanislav PECHEV, Corine Mathonière and Tahar MHIRI, Crystal Structure and magnetic properties of the bis tetrapropylammonium Hexachlorodicuprate(II): [N(C3H7)4]2Cu2Cl6 A15 Amy Poole, Bertrand Roessli, Peter Babkevich, Andrew Boothroyd, Jonathon White, Michel Kenzelmann, Tom Fennell, SNP@PSI: experiments performed with MuPAD at the Paul Scherrer Institut A16 N. A. Grigoryeva, S. V. Grigoriev, K. S. Napol’skii, A. P. Chumakov, A. A. Eliseev, I. V. Roslyakov, H. Eckerlebe, and A. V. Syromyatnikov, Polarized SANS study of spatially ordered arrays of interacting nanowires A17 Thomas Maurer, Fatih Zighem, S. Gautrot, Frédéric Ott, Grégory Chaboussant, Spatially Ordered Magnetic Nanowires investigated by Polarized SANS A18 L. J. Chang, S. Onoda, Y. Su, Y. –J. Kao, Y. Yasui, The transition from magnetic Coulomb phase to Higgs phase in the quantum spin ice Yb2Ti2O7 A19 J. Repper, T. Kellerb, W.W. Schmahl, High-resolution neutron Larmor diffraction for phase transition studies of LaAlO3 A20 Udalov Oleg, Skew scattering of cold unpolarized neutrons in ferromagnetic crystal A21 V. Runov, D. Ilyin, M. Runova, A. Radzhabov, Observation of ferromagnetic correlation caused by 3d admixture in nonmagnetic material by means of small-angle polarized neutron scattering A22 Felix Groitl, Katharina Rolfs, Diana Quintero-Castro, Klaus Kiefer, Thomas Keller, Klaus Habicht, Larmor labeling methods: Neutron Resonance Spin Echo spectroscopy beyond standard line width measurements A23 Chin Shan Lue, L. J. Chang, M. Takeda, C. H. Lee, G. Chern, Magnetic anisotropy in the interface of Fe3O4/Mn3O4 superlattices probed by neutron reflectivity A24 S.L. Holm, L. Udby, J. Larsen, N.B. Christensen, S.B. Emery, Y.F. Nie, N.H. Andersen, J.-G. Grivel, Ch. Niedermayer, B.O. Wells, and K. Lefmann, Field-induced magnetism in super-oxygenated (La,Sr)2CuO4+y A25 Yu.N. Khaydukov R.O. Tsaregorodsev, B. Nagy, L. Bottyán, Yu.V. Nikitenko, V.L. Aksenov, Waveguide-enhanced polarized neutron reflectometry: a new approach in the study of magnetic proximity effects. A26 D. Lamago, S. Krannich, Y. Sidis, F.Weber, J.M. Mignot, A.Ivanov, Spin Correlations in an Unconventional Metal by Polarized Neutron Scattering.

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Poster Session B, Wednesday, July 04th 2012

B01 Christoph Gösselsberger, Gerald Badurek, Erwin Jericha, Sebastian Nowak, Wavelength-selected neutron pulses formed by a spatial magnetic neutron spin resonator B02 Alexander GRÜNWALD, A.C. Komarek, S. Giemsa, P. Böni, M. Braden, KOMPASS – the new three-axes-spectrometer with 3D spherical polarization analysis to-be at FRM-II B03 T. Ino, Y. Arimoto, H. Kira, Y. Sakaguchi, T. Shinohara, K. Sakai, T. Oku, K. Kakurai, K. Ohoyama, Precise magnetic field mapping for the 3He neutron spin filter B04 K. Ohoyama, T. Yokoo, S. Itoh, J. Suzuki, K. Iwasa, K. Tomiyasu, M. Matsuura, H. Hiraka, M. Fujita, H. Kimura, H. Kira, Y. Sakaguchi, T. Ino, T. Oku, Y. Arimoto, T. Sato, T.J. Sato, K. Kaneko, J. Suzuki, H.M. Shimizu, T. Arima, M. Takeda, M. Hino, S. Muto, H. Nojiri, Polarisation Analysis Neutron Chopper Spectrometer, POLANO, at J-PARC B05 K. Ohoyama, K. Tsutsumi, T. Ino, H. Hiraka, Y. Yamaguchi, H. Kira, T. Oku, Y. Sakaguchi, Y. Arimoto, W. Zhang, H. Kimura, K. Iwasa, M. Takeda, J. Suzuki, K. Yamada, K. Kakurai, Development of a Polarised Neutron Diffraction System with a 3He Spin Filter on a Powder Diffractometer in JRR-3 B06 Georg Brandl, Tobias Weber, Wolfgang Häußler, Robert Georgii, Peter Böni, Monte-Carlo simulations for the optimization of a MIEZE spin-echo instrument at the ESS B07 J.G.Donaldson, S.Boag, P.Manuel, J.R.Stewart, J.W.Taylor, Initial Results of Uniaxial Polarisation Analysis on the WISH Diffractometer B09 P. Baroni, L. Noirez, G. Exil, A. Laverdunt, Using Light to see Neutrons: a New 2D-Detector with High Resolution at the Lab. Léon Brillouin B10 T. Yokoo, K. Ohoyama, S. Itoh, S. Ishimoto, H. Kira, Y. Sakaguchi, T. Ino, T. Oku, Y. Arimoto, M. Takeda, M. Hino, S. Muto, Neutron Polarizations in POLANO Project at J-PARC B11 Wai Tung Lee, Frank Klose, David Jullien, Pierre Courtois, Ken Andersen, Up-Coming Polarised Neutron Capabilities on ANSTO Instruments Using Polarised 3He Neutron Spin Filters (94) B12 H.Kira, Y.Sakaguchi, J. Suzuki, K.Sakai, T.Shinohara, T.Oku, M.Nakamura, M.Arai, Y.Endo, K.Kakurai, Y.Arimoto, T.Ino, H. Hiraka, K.Ohoyama, H.M. Shimizu, L.J. Chang, Magnetic shield design of in-situ SEOP polarized 3He neutron spin filter system B13 W.C. Chen, Q. Ye, and T.R. Gentile,

3He Polarization over 80% in Large Spin Filters Polarized by Hybrid Spin-Exchange Optical Pumping B14 W.C. Chen, S.M. Watson, K.L. Krycka, J.A. Borchers, and R. W. Erwin, Characterization of Spatial Uniformity of Neutron Polarization for a Polarized 3He Based SANS Spin Analyzer

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B15 S.Boag, D.Jullien, J.Donaldson, S.Marty, P.Mouveau, J.R.Stewart, J. Taylor, First results from Flynn: A new polarized 3He Filling Station B16 P. Courtois, D. Jullien, E. Lelièvre-Berna, P. Mouveau, A. Petukhov, A new-generation polarised 3He filling station developed at ILL B17 Kaoru Taketani, Spin flip chopper using Landau-Zener-Stückelberg Interferometry B18 S.R.Parnell, H.Kaiser, F.Li, T.Wang, D.V.Baxter, W.A.Hamilton and R.Pynn, Design and performance of a cryo-flipper using a YBCO film B19 Raul Victor Erhana, Sergey Manoshin and Alexander Belushkin, Simulations of a neutron spin echo spectrometers and its components using pulsed magnetic fields by VITESS software package B20 T. Bigault, D. Jullien, B. Farago, P. Falus, Performance of IN15 polarizing and analysing supermirror devices B21 Syromyatnikov V.G., Ulyanov V.A., Lauter V., Bulkin A.P., Pusenkov V.M., Wide-aperture fan neutron supermirror analyzer of polarization for Magnetism Reflectometer B22 Syromyatnikov V.G., Schebetov A.F., Pusenkov V.M., Pleshanov N.K., Serebrov A.P., Bulkin A.P., Neutron-optical system of the channel GEK- 4-4’ of reactor PIK B23 H. Hayashida, M. Takeda, D. Yamazaki, R. Maruyama, K. Soyama, M. Kubota, T. Mizusawa, Y. Sakaguchi and N. Yoshida, Design study of neutron spin flippers for a new neutron reflectometer at J-PARC B24 Zahir SALHI, Earl BABCOCK, Alexander IOFFE, Design study of magnetic environments for XYZ polarization analysis using 3He for the new thermal time of flight spectrometer TOPAS B25 Juan Rodriguez-Carvajal, Oksana Zaharko, Solving and Refining Magnetic Structures by Combined Polarimetry and Integrated Intensity data B26 Klimko Sergey, Longeville Stephane, Malikova Natalie, Development of RF-flippers for large angle NRSE

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Monday, July 2nd 2012

SESSION: Geometrical frustration

Chair: I. Mirebeau

Magnetricity and Magnetic Monopoles in Spin ice

S. T. Bramwell London Centre for Nanotechnology and DepartMent of Physics and Astronomy, University College London

The analogy between spin configurations in spin ice materials like Ho2Ti2O7 and proton configurations in water ice, H2O, has been appreciated for many years (see Ref. [1] for a review). However it is only in the last few years that this equivalence has been extended into the realm of electrodynamics [2,3]. In this talk I shall describe our recent experimental work that identifies emergent magnetic charges ("monopoles"), transient magnetic currents ("magnetricity") and the universal properties expected of an ideal magnetic Coulomb gas (magnetic electrolyte - "magnetolyte"). These universal properties include the Onsager-Wien effect, "corresponding states" behaviour, Debye-Huckel screening and Bjerrum pairing [4-6]. I will describe experimental results for both traditional spin ice materials (Ho2Ti2O7, Dy2Ti2O7) and a recently discovered system (Dy2Ge2O7).

References: [1] Bramwell and Gingras, Science, 294 1495 2001 [2] Castelnovo et al., Nature 451 42 (2008) [3] Ryzhkin, JETP 101 481 (2005); [4] Bramwell et al. Nature 461 956 (2009) [5] Fennell et al., & Bramwell Science 326 415 (2009) [6] Giblin, Bramwell et al., Nature Physics 7 252 (2011) [7] Zhou, Bramwell et al., Nat Comm. 478, 1483 (2011)

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Disorder in the Laves phase compound ZrMn2

P. P. Deen, J. Taylor, A. D. Hillier, A. D. Strydom , M. Rotter and H. Mutka

.

1 European Spallation Source, Tunavägen 24 Lund, Sweden. 2 Rutherford Appleton Laboratory, STFC, Didcot, United Kingdom.

3 University of Johannesburg, South Africa. 4 M. Rotter, Max Planck Institute, Dresden, Germany.

5 Institut Laue Langevin, Grenoble, France.

The interplay between disorder and quantum fluctuations is an exciting topic in quantum many body physics. The introduction of disorder tends to hamper the development of static ordered phases and can lead to a variety of exotic phases including spin liquids (a form of dynamic magnetic disorder on a quantum level), quantum glassy behaviour ( static magnetic disorder) and quantum Griffiths phases in which a strongly correlated electronic liquid can be found in a non-correlated matrix [1].

ZrMn2 sits firmly in the family of exotic magnetic orders that have been found in the transition metal Laves phases. For instance, in YMn2 heavy fermion behaviour co-exists with 3D spin liquid order [2,3] while NbFe2 sits in the proximity of a three dimensional ferromagnetic quantum critical point [4].

The first magnetization and paramagnetic susceptibility measurements on ZrMn2 by Shavishvili [5], yielded, rather surprisingly, a large effective magnetic moment of 2.4 μB per Mn atom. However, such a large effective Mn moment is in conflict with the experimental results by Jacob, who concluded that ZrMn2 was paramagnetic [6]. Theoretical calculations on the elec- tronic structure and magnetic properties of ZrMn2 led to a variety of claims on the ground state ranging from a mainly paramagnetic state [7], a ferromagnetic ground state nearly degenerate with a paramagnetic ground state [8] to a prediction of a strong competition between antiferro- magnetic and ferromagnetic interactions leading to geometrical frustration of the Mn moments [9]. To date, none of these magnetic states have been uncovered [10].

In this work we have uncovered, via specific heat and susceptibility measurements in addition to inelastic scattering and muon spin relaxation, a highly disordered yet strongly correlated compound with quantum correlations. As such ZrMn2 provides a unique opportunity to study the low temperature behaviour of quantum many particle systems in the vicinity of disorder.

[1] T. Vojta et al. Phys. Rev. B. 72 045438 (2005). [2] R. Ballou et al. Phys. Rev. Lett. 76 2125 (1996). [3] B. Canals et al. Phys. Rev. Lett. 80 2933 (1998). [4] M. Brando et al. Phys. Rev. Lett. 101 026401 (2008). [5] T. M. Shavishvili Fiz. Met. Metalloved. 47880 1979. [6] I. Jacob et al. J. Magn. Magn. Mater. 20226 (1980). [7] S. Ishida et al. J. Phys. Soc. Jpn 54, 3925 (1985). [8] S. Asano et al. J. Magn. Magn. Mater. 70, 39 (1987). [9] X. Q. Chen et al. Phys. Rev. B 72, 054440 (2005). [10] M. Rotter et al. Phys. Rev. B. 74, 224109 (2006).

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Higgs transition from magnetic Coulomb liquid to ferromagnet in Yb2Ti2O7

Lieh-Jeng Chang1,2

, Shigeki Onoda3, Y. Su

4, Y.-J. Kao

5, K.-D. Tsuei

6, Y. Yasui

7, K. Kakurai

2, M. R. Lees

8

1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan 2Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan3Condensed Matter Theory Laboratory, RIKEN, Wako 351-0198, Japan, s.onoda@riken.jp 4Jülich Centre for Neutron Science JCNS-FRM II, D-85747 Garching, Germany 5Department of Physics, National Taiwan University, Taipei 10607, Taiwan 6National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan 7Department of Physics, Division of Material Science, Nagoya University, Nagoya 464-8602, Japan 8Department of Physics, University of Warwick, Coventry CV4 7AL, UK In quantum variants of spin ice, it is expected that emergent magnetic monopole charges are carried by fractionalized bosonic quasi-particles, spinons, which can undergo Bose-Einstein condensation via the Higgs mechanism. Here, we report evidence of such first-order phase transition from a magnetic Coulomb liquid to a ferromagnet in single-crystal Yb2Ti2O7. Our polarised neutron-scattering experiments show that the diffuse [111]-rod scattering and the remnant of pinch-point singularity, whose intensities grow with decreasing temperature, are suddenly suppressed below Tc～0.21 K where magnetic Bragg peaks and a full depolarisation of neutron spins are observed with thermal hysteresis, indicating a first-order ferromagnetic transition. Our results are explained from a quantum spin-ice model, whose high-temperature phase is described as a magnetic Coulomb liquid, while the ground state shows a nearly collinear ferromagnetism with gapped spin excitations. References

[1] L.-J. Chang, S. Onoda, Y. Su, Y.-J. Kao, K.-D. Tsuei, Y. Yasui, K. Kakurai, M. R. Lees, arXiv:1111.5406.

The transition from magnetic Coulomb phase to Higgs phase in the quantum spin ice Yb2Ti2O7

L. J. Chang, S. Onoda1, Y. Su

2, Y. –J. Kao

3, Y. Yasui

4

Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan ljchang@mail.ncku.edu.tw, 1Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan

2Jülich Centre for Neutron Science JCNS-FRM II, Forschungszentrum Jülich GmbH, Outstation at FRM-II, Lichtenbergstrasse 1, D-85747 Garching, Germany

3Department of Physics, National Taiwan University, Taipei 10607, Taiwan 4Department of Physics, Division of Material Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,

Japan Polarized neutron-scattering experiments had been carried out on single crystal Yb2Ti2O7 in a 3He-dilution refrigerator from 1.5 K to 0.04 K. The results reveal that the diffuse [111]-rod scattering [1] is suppressed below Tc ~ 0.21 K, where magnetic Bragg peaks and a full depolarization of neutron spins are observed with the thermal hysteresis, indicating a first-order ferromagnetic transition. The transition from magnetic Coulomb phase to Higgs phase in a quantum spin-ice model [2] is adapted to explain the consequences. Pinch points are observed in both experimental and theoretical results to suggest its quantum spin ice state. This has been understood theoretically from an effective classical model where <111> Ising moments, i.e., pseudospin-1/2 interact mainly through a magnetic dipolar interaction [3], showing anisotropic and power-law decaying dipolar spin correlations [4].

References [1] K. A. Ross et al., Phys. Rev. Lett. 103, 227202 (2009). [2] L. J. Chang et al., arXiv: 1111.5406. [3] S. T. Bramwell and M. J. P. Gingras, Science 294, 1495 (2001). [4] S. V. Isakov et al., Phys. Rev. Lett. 93, 167204 (2004).

16

Session: Frustration and Chirality

Chair: I. Mirebeau

Chirality in Fe-langasite

Virginie Simonet1, Mickaël Loire

1, Karol Marty

1, Eric Ressouche

2, Sylvain Petit

3, Pierre Bordet

1, Pascal Lejay

1,

Jacques Ollivier4, Mechtild Enderle

4, Paul Steffens

4, Rafik Ballou

1

1Institut Néel, CNRS&UJF, BP166, 38042 Grenoble Cedex 9, France, virginie.simonet@grenoble.cnrs.fr 2Institut Nanosciences et Cryogénie, SPSMS/MDN, CEA-Grenoble, 38054 Grenoble, France

3Laboratoire Léon Brillouin, CEA-CNRS, CE-Saclay, F-91191 Gif sur Yvette, France 4Institut Laue Langevin, BP156, 38042 Grenoble Cedex 9, France

A novel doubly chiral magnetic order is found in the structurally chiral langasite compound Ba3NbFe3Si2O14 [1]. The magnetic moments are distributed over planar frustrated triangular lattices of triangle units. On each of these they form the same triangular configuration. This ferrochiral arrangement is helically modulated from plane to plane. Unpolarized neutron scattering on a single crystal associated with spherical neutron polarimetry proved that a single triangular chirality together with a single helicity is stabilized in an enantiopure crystal. A mean-field analysis allowed establishing the link between the structural and magnetic chiralities. The spin-wave excitations emerging from this chiral ground state were investigated by unpolarized and polarized inelastic neutron scattering. A dynamical fingerprint of the chiral ground state is obtained, singularized by (i) spectral weight asymmetries due to the structural chirality and (ii) a full chirality of the spin correlations observed over the whole energy spectrum. The intrinsic chiral nature of the spin waves’ elementary excitations is shown in the absence of macroscopic time-reversal symmetry breaking [2].

References [1] K. Marty, et al., Phys. Rev. Lett. 101 (2008) 247201 (2008). Single Domain Magnetic Helicity and Triangular Chirality in Structurally Enantiopure Ba3NbFe3Si2O14

[2] M. Loire, et al., Phys. Rev. Lett. 106 (2011) 207201 (2011). Parity-Broken Chiral Spin Dynamics in Ba3NbFe3Si2O14

17

The hexagonal spin structure of A-phase in MnSi

S.V. Grigoriev,1 N.M. Potapova,

1 E.V. Moskvin,

1 V.A. Dyadkin,

1 Ch. Dewhurst,

2 S.V. Maleyev

1

1 Petersburg Nuclear Physics Institute, Gatchina, Saint-Petersburg, 188300, Russia

1 Institute Laue-Langevin, F-38042 Grenoble Cedex 9, France

Inspired by recent work [1] we have revisited the cubic helimagnet MnSi to address the question of the origin of A-phase in the (H-T) phase diagram. The A-phase revealed itself on the neutron diffraction map as a hexagonal pattern of Bragg spots with kA ⊥ H in a narrow range of the fields [0.12 - 0.20] T close to Tc = 29 K for three principal crystal-to-field orientations (H || [111], H || [110], H || [100]). The orientational and translational orders (the directions and value of structure wavevectors kA) are well preserved within the A-phase over the whole crystal of the size of 100 mm3. The small angle neutron scattering ascribed to the orientationally disordered hexagon spin structure was observed beyond the A-phase boundaries in the field range from HT1 = 0.1 T to HT2 = 0.25 T at temperatures down to 15 K. Contrary to the A-phase boundaries, the values of HT1 and HT2 are both temperature independent and independent on the field-to-crystal orientation. The A-phase surrounded by the cone phase with kc || H for the low and high fields near TC as well as for all fields at low temperatures. The magnetic system undergoes clearly the first order phase transition from cone phase to the A-phase and back upon the field enhancement, so that two phases coexist within the whole A-phase region. We discuss the applicability of existing theories to interpret our results.

References

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A. Neubauer, R. Georgii, P. Böni, Science 323 (2009) 915-919.

Chirality effects in Rare-Earth Multilayers investigated by polarized neutrons

D. Lott, S. Grigoriev, E. Kenntzinger, A. Gruenwald, E. V. Tartakovskaya

, V. Kapaklis, A. Schreyer

Helmholtz Zentrum Geesthacht, 21502 Geesthacht, German, dieter.lott@hzg.de Petersburg Nuclear Physics Institute, 188300 Gatchina, Russia,

Forschungszentrum Jülich, Institut für Festkörperforschung, D-52425 Jülich, Germany Institute for Magnetism of National Ukrainian Academy of Science, 03142 Kiev, Ukraine

Uppsala University, Department of Physics and Astronomy, Box 516, 75120 Uppsala, Sweden Clarendon Laboratory, Oxford University, South Parks Rd, Oxford, United Kingdom

The presence of chirality plays a crucial role in many different disciplines in science and is often the key to understand phenomena in nature. In the recent years the chirality effect has finally also caught a lot of intention in the field of magnetism, particularly, when it could be linked to the appearance of the Dzyaloshinskii-Moriya (DM) interaction.

Here we report about our investigations of this intriguing phenomena in rare-earth multilayer in whose the chirality can be tuned by the application of an external magnetic field. Polarized neutron refelctometry is the tool of choice to study the dependence on composition, temperature and magnetic field [1,2]. The interplay of the RKKY and the Zeeman interactions helps here to reveal the anti-symmetric Dzyaloshinskii-Moriya interaction since the observed chirality is a fingerprint of the DM interaction resulting from the lack of the symmetry inversion at the interfaces. Careful analysis of the polarized neutron measurements with complete polarization analysis allows one to link the occurrence of the effect with changes in the magnetic structure.

[1] S.V.Grigoriev, Yu.O. Chetverikov, D.Lott, A. Schreyer, Phys. Rev. Lett. 100, 197203. (2008) [2] S.V.Grigoriev, D. Lott,2 Yu. O. Chetverikov,1 A. T. D. Grünwald, R. C. C. Ward, and A. Schreyer, Phys. Rev. B 82,

195432 (2010).).

18

Spherical neutron polarimetry with MiniMuPAD: Investigations of the transition from heli- to paramagnetism in MnSi

J. Kindervater, W. Häußler, C. Pfleiderer and P. Böni Physik Department E21, Technische Universität München, James-Franckstr. 1, 85747 Garching, Germany,

jonas.kindervater@frm2.tum.de

Chiral magnets such as the B20 compound MnSi and related materials have recently attracted much scientific interest because new spin structures as for example the skyrmion lattice have been identified [1]. This topological stable spin texture occurs under the application of moderate magnetic fields. Besides these topological spin textures the phase transition from heli- to paramagnetism in MnSi is under active scientific discussion. Different scenarios for the precise nature of the transition have been proposed, ranging from a topological skyrmion liquid phase over a second order mean field transition to a fluctuation induced first order phase transition [2,3].

We report on measurements in a SANS geometry using the newly developed device "MiniMuPAD". MiniMuPAD allows an simple implementation of spherical neutron polarimetry on different neutron scattering instruments, in particular SANS instruments. We proof the reliability of the new technique by validating our data with existing data. In order to resolve the nature of the phase transition we focus on the investigation of the chiral fraction in MnSi.

References

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A. Neubauer, R. Georgii and P. Böni. Science, 323(5916):915919, 2009. [2] C. Pappas, E. Lelievre-Berna, P. Falus, P. M. Bentley, E. Moskvin, S. Grigoriev, P. Fouquet, and B. Farago. Phys. Rev. Lett., 102(19):197202, May 2009. [3] S. V. Grigoriev, S. V. Maleyev, A. I. Okorokov, Yu. O. Chetverikov, R. Georgii, P. Böni, D. Lamago, H. Eckerlebe, and K. Pranzas. Phys. Rev. B, 72(13):134420, Oct 2005. D. Lamago, H. Eckerlebe, and K. Pranzas. Critical polarized neutron scattering study. Phys. Rev. B, 72(13):134420, Oct 2005.

Polarised neutron scattering from skyrmions

R. Georgii, T. Adams, P. Böni, G. Brandl, W. Häußler, J. Kindervater, C. Pfleiderer

Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universität München, Lichtenbergstr.1, 85748 Garching, Germany, Robert.Georgii@frm2.tum.de

Physik Department E21, Technische Universität München, James-Franckstr., 85748 Garching, Germany

Since the discovery of skyrmions in the A-phase of MnSi [1] similar structures where found in a wide field of materials ranging from metals over semiconductors to insulators [2]. Polarised neutron scattering on theses structures can give import information on the chirality of the skyrmions. Furthermore using the MIEZE technique information on the dynamical properties can be obtained.

After an overview of skyrmions we will discuss polarized SANS on these structures and will show the importance of high-resolution spin echo measurements using the MIEZE principle. This will lead to a proposal for a dedicated NRSE-MIEZE instrument at the ESS.

References

[1] S. Mühlbauer, B. Binz, F. Jonietz, C. Pfleiderer, A. Rosch, A. Neubauer, R. Georgii und P. Böni, Science 323 (2009) 915 – 919. Skyrmion Lattice in a Chiral Magnet.

[2] W. Münzer, A. Neubauer, S. Mühlbauer, F. Franz, T. Adams, F. Jonietz, R. Georgii, P. Böni, B. Pedersen, K. Schmid et al., Physical Review B 81 41203(R). Skyrmion lattice in the doped semiconductor Fe1−xCoxSi.

19

SESSION: Multiferroics And Chirality

CHAIR: J. Rodrigues-Carjaval

Polarised neutron-scattering investigations on chiral multiferroics

M. Braden1, M. Baum1, S. Holbein1, J. Stein1, D. Senff1, Th. Finger1, A.C. Komarek1, N. Aliouane2, D. Argyriou2, A. Hiess3, K. Schmalzl3, L.P. Regnault3, P. Link4, K. Hradil4, Y. Sidis5, P. Becker- Bohatý 6, L. Bohatý6, J. Leist7,

and G. Eckold7

1II. Physik. Institut, Köln; 2Helmholtz-Zentrum Berlin; 3Institut Laue Langevin, Grenoble; 4FRM-II, Garching; 5Laboratoire Léon Brillouin, Saclay; 6Inst. f. Krist., Köln; 7Institut f. Physik. Chemie, Göttingen. E-mail: braden@ph2.uni-koeln.de

Neutron scattering with spherical polarization analysis is the ideal tool to analyze chiral magnetism. In multiferroics one may follow chiral components as function of temperature and electric field and thereby directly study the multiferroic hysteresis curves versus electric field [1]. In MnWO4 the electric-field induced switching of the chiral magnetism has been also studied with a stroboscopic technique revealing remarkably slow dynamics of multiferroic domains. The time constants of the chiral switching in MnWO4 are of the order of milliseconds. Combining unpolarized and polarized neutron scattering studies, the frequencies and polarization patterns of the magnetic excitations can be determined. Evidence for an electromagnon, a hybridized phonon-magnon excitation, is obtained in TbMnO3 [2] and will be discussed in comparison to the recent infra-red reflectivity measurements. The phason-type magnetic excitations in TbMnO3 are chiral for a propagation vector close to the magnetic zone centres, but the chiral component is suppressed in the Brillouin zone and even modes with opposed chirality are observed. TbMnO3 also exhibits diffuse chiral scattering around the ferroelectric transition which can be poled by an electric field. First results about controlling ferrotoroidal domains by the application of vertical electric and magnetic fields will be discussed.

References

[1] T. Finger et al., Phys. Rev. B 81, 054430 (2010).

[2] D. Senff et al., Phys. Rev. Lett. 98, 137206 (2007).

20

Electric field control of the magnetic chiralities in ferroaxial multiferroic RbFe(MoO4)2

Laurent C. Chapon, Alexander J. Hearmon, Federica Fabrizi,, R. D. Johnson, Dharmalingam Prabhakaran, P. J. Brown, Paolo G. Radaelli

Institute Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France Clarendon Laboratory, Department of Physics,

University of Oxford, Parks Road, Oxford OX1 3PU, UK Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK

ISIS Facility, STFC-Rutherford Appleton Laboratory, Didcot, OX11 OQX, UK

Abstract text The coupling of magnetic chiralities to the ferroelectric polarisation in multiferroic RbFe(MoO4)2 is investigated by neutron spherical polarimetry. Because of the axiality of the crystal structure below Tc = 190 K, helicity and triangular chirality are symmetric-exchange coupled, explaining the onset of the ferroelectricity in this proper-screw magnetic structure a mechanism that can be generalised to other systems with “ferroaxial" distortions in the crystal structure. With an applied electric field we demonstrate control of the chiralities in both structural domains simultaneously[1

References

[1] . arXiv:1202.2317, accepted in PRL (April 2012)

Spin dynamics in multiferroic RMnO3

Xavier Fabrèges1,2

, Isabelle Mirebeau1, Julien Robert

1, Loreynne Pinsard

3,and Sylvain Petit

1

LLB, CE-Saclay, 91191 Gif sur Yvette, France

2 LNCMI, 143 avenue de Rangueil, 31400 Toulouse, France

3 ICMMO, Université Paris-Sud, 91400 Orsay, France

Hexagonal RMnO3 (with R elements having small ionic radii, R = Ho, Er, Yb, Lu, Y) form a class of triangle-based multiferroic materials [1], which have been widely studied in the recent years. Magnetic frustration combined with a striking magneto-elastic coupling seems to be at the origin of their properties, a cocktail that has a strong potential for novel physics. Here, we report on neutron scattering experiments carried out to study the structure and spin dynamics in this series of compounds. The magnetic excitations spectra can be accounted for by spin wave calculations in the Holstein-Primakov approximation, leading to a precise knowledge of the exchange coupling and anisotropy parameters [2]. Meanwhile, the Néel order at 120° imposed by the geometric frustration is accompanied by an isostructural transition: each ion “moves” inside the unit cell when Mn moments get ordered [3,4]. We can correlate the atomic positions, the type of magnetic structure and the nature of the spin waves whatever the R ion and temperature. We show that the key parameter is the position of Mn ions within the hexagonal plane with respect to a critical threshold [6]. Using polarized neutrons, we also report data compatible with an hybridization of spin and lattice elementary excitations [4], possibly related to the so called electro-magnons [5,6].

References

[1] Cheong S.W and Mostovoy M. Nature materials, 6, 13 (2007) [2] S. Petit el al, PRL 99, 266604 (2007), [3] S. Lee et al. Nature 451,805 (2008),[4] X. Fabrèges et al, PRL 103, 067204 (2009), [5] S. Pailhès et al, PRB 79, 134409 (2009) [8] Pimenov et al., Nature Physics, Vol 2, February 2006,[9] H. Katsura et al., PRL, 98, 027203 (2007)

21

From Liquid Crystals to Chiral Magnets

C.Pappas1, E. Lelièvre-Berna

2, P. Falus

2, P. Fouquet

2, D. Schlagel

3 and T. Longrasso

3

1Delft University of Technology, Mekelweg 15, 2629 JB Delft, the Netherlands

2Institut Laue Langevin, 6 Rue J.Horowitz, Grenoble, 38042, France

3Ames Laboratory, Iowa State University, Ames, IA 50011, USA

Most modern electronic displays use chiral liquid crystals and their interaction with polarised light to produce colourful pictures. Chiral magnets interact in a similar way with polarised neutron beams and if the result is not as flashy as LCD screens, it sheds a light into chiral magnetism revealing its strong analogies to chiral nematic phases. In spite of the different topologies both systems favor the formation of similar mesoscopic chiral objects, which are extremely stable at short distances. Polarised neutrons shed a light on these objects in the reference chiral magnet MnSi, which sprout and condensate by completely filling the space when lowering the temperature. This condensation affects all thermodynamic and transport properties and appears as a major transformation with some characteristics of a phase transition. Similarly to liquid crystals, the resulting phase combines liquid and solid properties. The effect of external pressure and magnetic fields on this phase will also be discussed.

Resonance mode in rare-earth systems with valence instability

Kirill Nemkovski1, Pavel Alekseev

2, Jean-Michel Mignot

3

1Forschungszentrum Jülich, JCNS, Outstation FRM II, Germany, k.nemkovskiy@fz-juelich.de 2National Research Centre “Kurchatov Institute”, Moscow, Russia

3Laboratoire Léon Brillouin, CEA-CNRS, CEA/Saclay, France

An extended study of the spin dynamics in the Kondo-insulator YbB12 [1], as well as in the Sm- and Eu-based unstable-valence systems SmB6 [2], Sm1-xYxS [3] and EuCu2SixGe1-x [4], has been performed by means of inelastic neutron scattering spectroscopy, including neutron polarization analysis. The results of [1-4], along with new experimental data, clearly show that rare-earth (RE) compounds with a valence instability may demonstrate an exciton-like in-gap excitation, generally similar (though different in some details) to the so-called resonance mode in HTSC. The observed excitations can be classified into two types: (1) excitations based on a charge exciton with intermediate radius in systems with “strong” intermediate valence; (2) spin-exciton-like excitations arising from dynamical antiferromagnetic correlations between the localized magnetic moments of the RE ions. The possible role of an interplay with lattice degrees of freedom is also discussed.

The results obtained point to such type of resonance excitations being characteristic for strongly correlated electron systems with gap-like dynamical response in the presence of competing interactions.

References

[1] K. S. Nemkovski, J.-M.Mignot, P.A.Alekseev et al., Phys.Rev. Lett. 99, 137204 (2007). [2] P. A. Alekseev, J.-M. Mignot, J. Rossat-Mignod et al., J. Phys.: Condens. Matter 7, 289(1995). [3] P. A. Alekseev, J.-M. Mignot, E. V. Nefeodova, K. S. Nemkovski et al., Phys. Rev. B 74 035114 (2006) [4] P. A. Alekseev, K. S. Nemkovski, J.-M. Mignot et al., Magnetic excitations in EuCu2(SixGe1-x)2 : from mixed valence towards magnetism, to be published.

22

Tuesday, July 3rd 2012

Session: Strongly correlated electron systems and polarisation,

Chair: Ph. Bourges

Novel Magnetism in the Pseudogap Phase of the Cuprates

Mun K. Chan*,†

School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, US.

mchan@physics.umn.edu

Magnetic correlations might cause the superconductivity in the cuprates and are generally believed to be antiferromagnetic. Following our success in growing sizable crystals of the tetragonal compound HgBa2CuO4+δ [1], we used polarized neutron diffraction to demonstrate that the unusual magnetic order previously observed in YBa2Cu3O6+δ [2] is a universal property of the pseudogap phase [3]. Subsequent inelastic neutron scattering experiments revealed several accompanying, weakly-dispersive magnetic excitation branches in HgBa2CuO4+δ [4]. Unlike antiferromagnetism, the novel magnetic order does not break the lattice translational symmetry. Nevertheless, the excitations mix with conventional antiferromagnetic fluctuations. Our results point toward the need for a multi-band description of the cuprates, and they are consistent with the notion that the phase diagram is controlled by an underlying quantum critical point [5].

*Work performed in collaboration with Y. Li, G. Yu, V. Balédent, Yangmu Li, N. Barišic, X. Zhao, K. Hradil, R. A. Mole, Y. Sidis, P. Steffens, P. Bourges and M. Greven.

† This research was supported by the US Department of Energy, Office of Basic Energy Sciences

References

[1] X. Zhao et al., Adv. Mat. 18, 3243 (2006) [2] B. Fauqué et al., Phys. Rev. Lett. 96, 197001 (2006) [3] Y. Li et al., Nature 468, 283 (2010); Y. Li et al. Phys. Rev. B 84, 224508 (2011) [4] Y. Li et al., Nature 455, 372 (2008); Y. Li et al. Nature Physics 8, 404 (2012) [5] C. Varma, Nature 468, 184 (2010)

23

Spin anisotropy of the resonance peak in unconventional superconductors

A.T. Boothroyd1, P. Babkevich

1,2, B. Roessli

2, S.N. Gvasaliya

3, L.-P. Regnault

4, P.G. Freeman

5,

E. Pomjakushina6, K. Conder

6

1Department of Physics, University of Oxford, U.K., a.boothroyd@physics.ox.ac.uk 2Laboratory for Neutron Scattering, Paul Scherrer Institut, Switzerland

3Institut for Solid State Physics, ETH-Zürich, Switzerland 4CEA/Université Joseph Fourier, Grenoble, France

5Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany 6Laboratory for Development and Methods, Paul Scherrer Institut, Switzerland

The resonance peak is a superconductivity-induced enhancement of the spin excitation spectrum at a well-defined energy and wavevector, found in several families of unconventional superconductors. The origin of the resonance peak remains a matter of debate, but it is thought to relate to the superconducting pairing state and gap symmetry. We have used polarisation neutron scattering to study the low energy spin fluctuations and resonance peak in superconducting FeSe0.5Te0.5. By resolving the spin correlations along different directions we find that the spin fluctuations are isotropic above and below the resonance peak, but we find a small spin anisotropy on the resonance peak itself. I will discuss the implications of these results for the superconducting pairing symmetry. I will also present calculations of the spin anisotropy of the magnetic excitations in the copper oxide superconductors, and compare the results with recent polarised neutron scattering measurements. [1] P. Babkevich, B.Roessli, S.N. Gvasaliya, L.-P. Regnault, P.G. Freeman, E. Pomjakushina, K. Conder, and A.T. Boothroyd, Phys. Rev. B 83 (2011) 180506(R). Spin anisotropy of the resonance peak in superconducting FeSe0.5Te0.5

Structural and Antiferromagnetic Domains in Undoped YBa2Cu3O6

B. Náfrádi

1,2, T. Keller

2,3, F. Hardy

4, C. Meingast

4, A. Erb

5, B. Keimer

2

1Laboratory of Nanostructures and Novel Electronic Materials, EPFL CH-1015 Lausanne, Switzerland, nafradi@yahoo.com

2Max-Planck-Institut für Festkörperforschung, Heisenbergstrβe 1, D-70569 Stuttgart, Germany 3ZWE FRM II, TU München, Germany

4Institut für Festkörperphysik, Karlsruher Institut für Technlogie (KIT) D-76344 Eggenstein-Leopoldshafen, Germany 5Walter Meissner Institut für Tieftemperaturforschung D-85748 Garching, Germny

Undoped antiferromagnetic YBa2Cu3O6 exhibits orthogonal magnetic twin-domains in thermal equilibrium [1]. We have used a combination of neutron Larmor diffraction spectroscopy and capacitance dilatometry to determine the size, anisotropy and origin of the domain structure. We find a small (b-a)/b=2.6×10-6 orthorhombic structural-distortion, as a consequence of magnetostriction. The magnetic twinning is accompanied by structural twinning. Changes of magnetic domains by external field results rearrangement of structural domains. By applying Larmor diffraction method for measuring correlation lengths we determined the c-direction thickness of the antiferromagnetic domains as 230 nm. The orthogonal domains are alternating in the c direction. While the (a-b) plane size of the domains exceeds 104 unit cell. Models describing the unusual magnetoresistive anisotropy [2] are discussed. References [1] P. Burlet, J. Y. Henry, and L. P. Regnault, Physica C 296, 205 (1998). In-plane magnetic anisotropy in antiferromagnetic YBa2Cu3O6+x

[2] Y. Ando, A. N. Lavrov, and K. Segawa, Phys. Rev. Lett. 83, 2813 (1999). Magnetoresistance Anomalies in Antiferromagnetic YBa2Cu3O6+x: Fingerprints of Charged Stripes

24

Antiferromagnetic order and superlattice structure in nonsuperconducting and superconducting RbyFe1.6+xSe2 Meng Wang,1,2 Miaoyin Wang,2 G. N. Li,1,3 Q. Huang,3 C. H. Li,1 G. T. Tan,2,4 C. L. Zhang,2 Huibo Cao,5 Wei Tian,6 Yang Zhao,3,7 Y. C. Chen,1 X. Y. Lu,1 Bin Sheng,1 H. Q. Luo,1 S. L. Li,1 M. H. Fang,8 J. L. Zarestky,6 W. Ratcliff,3 M. D. Lumsden,5 J. W. Lynn,3 and Pengcheng Dai2,1

1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA 3NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA 4College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China 5Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA 6Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA 7Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA 8Department of Physics, Zhejiang University, Hangzhou 310027, China Neutron diffraction has been used to study the lattice and magnetic structures of the insulating and superconducting RbyFe1.6+xSe2. For the insulating RbyFe1.6+xSe2, neutron polarization analysis and single-crystal neutron diffraction unambiguously confirm the earlier proposed

√5 ×√5 block antiferromagnetic structure. For superconducting samples (Tc = 30 K), we find that in addition to the tetragonal √5 ×√5superlattice structure transition at 513 K, the material develops a separate √2 ×√2superlattice structure at a lower temperature of 480 K. These results suggest that superconducting RbyFe1.6+xSe2 is phase separated with coexisting √2 ×√2 and √5 ×√5 superlattice structures.

Spin-Peierls phase transition in CuGeO3 revisited in the light of polarized neutron scattering experiments

J.E. Lorenzo1 and L.P. Regnault

2

1 Institut Néel, CNRS et Université Joseph Fourier, F-38042 Grenoble France, 2 INAC-SPSMS-MDN, UMR-E CEA/UJF-Grenoble 1, Grenoble F38054, France

The spin-Peierls (SP) phase transition in CuGeO3 has raised a lot of attention in the 90's and overall it is a rather well understood subject [1]. The uniform quantum S=1/2 chain is unstable against lattice dimerizations that create an alternating magnetic exchange. As a result, S=1 dimers are spontaneously formed giving rise to a new ground state -the singlet- and a triplet of excitations as the excited states. Since the turn of the century new ideas and models have sparkled mainly regarding the nature of the phase transition and how different SP states can be thus created. On the other hand ideas borrowed from the newly developed field of quantum computation (such as entanglement and decoherence) have found their way in the actual world of quantum spin chains [2]. In this contribution, and following previously developed techniques [3], we will show how polarized inelastic neutron scattering methods can contribute to the understanding of the phase transition in CuGeO3. S=1 excitations can be 'easily' separated from the S=1/2 counterparts, thus allowing a clearer picture of how the spin-triplet excitation gap appears below the transition temperature. References [1] J.P. Boucher and L.P. Regnault, J. Phys. I France 6, 1939 (1996) [2] J.E. Lorenzo, et al., Phys. Rev. Lett. 105, 097202 (2010). [3] J.E. Lorenzo, et al., Phys. Rev. B 75, 054418 (2007).

25

Session: Strongly correlated electron systems and polarisation

Chair: G. Chaboussant

Polarized Neutron on URu2Si2.

F. Bourdarot, E. Ressouche,1 R. Ballou,

2 S. Raymond,

1 D. Aoki,

1 N. Martin,

1 L.-P. Regnault,

1 V. Simonet,

2 M.T.

Fernandez-Diaz,3 A. Stunault,

3 V. Taufour,

2 and J. Flouquet

2

SPSMS, UMR-E 9001, CEA-INAC/ UJF-Grenoble 1, frederic.bourdarot@cea.fr 1SPSMS, UMR-E 9001, CEA-INAC/ UJF-Grenoble 1, 17 rue des Martyrs, F-38054 Grenoble, France

2Institut Néel, CNRS & Université Joseph Fourier, BP166, 38042 Grenoble, France 3Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France

Polarized neutron scattering has shed a new light on URu2Si2. This compound studied for almost thirty years presents two transitions: a superconducting state below 1.2K (Tsc) and a well-defined-bulk transition at 17.8K (T0). In spite of intensive research, none local probe has defined the order parameter associated with this transition (the famous Hidden Order (HO)). Polarized inelastic neutron measurements have shown the existence of three different excitations, with only one vanishing at T0 and all between singlets levels[1]. Neutron Larmor diffraction measurement combined with uniaxial stress experiment have shown that the relevant parameter that governs the magnetic properties is the a-lattice parameter[2]. Induced magnetization measured by polarized neutron elastic scattering shows a subtle change in the distribution when entering in the HO state. An analysis in terms of U4+ ionic states suggest that this might be a fingerprint of a freezing of rank 5 multipoles (i.e. dotriacontapole). References [1] F. Bourdarot, E. Hassinger, S. Raymond, D. Aoki, V. Taufour, L.-P. Regnault, J. and Flouquet, JPSJ 79 (2010), 064719, Precise Study of the Resonance at Q0 = (1,0,0) in URu2Si2. [2] F. Bourdarot, N. Martin, S. Raymond, L.-P Regnault. D. Aoki, V. Taufour, and J. Flouquet, PRB 84, (2011), 184430. Magnetic properties of URu2Si2 under uniaxial stress by neutron scattering. [3] Ressouche, E., Ballou, R., Bourdarot, F., Aoki, D., Simonet, V., Fernandez-Diaz, M., Stunault, A., and Flouquet, J. Hidden order in URu2Si2 unveiled. Submitted to Nature, 2012.

26

Temperature dependence of magnon lifetimes in the quasi-2D collinear S=1 honeycomb-lattice

antiferromagnet BaNi2(PO4)2

N. Martin

1, L.P. Regnault

1 and S. Klimko

2

1 INAC-SPSMS-MDN, UMR-E CEA/UJF-Grenoble 1, Grenoble F38054, France 2Laboratoire Leon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif-sur-Yvette, France

References [1] L.P. Regnault and J. Rossat-Mignod, in Magnetic Properties of Layered Transition Metal Compounds, Ed. L.J. De Jongh (Kluwer Academic, 1990) p.271. [2] N. Martin, L.P. Regnault, S. Klimko, J.E. Lorenzo and R. Gähler, Physica B 406 (2011) 2333-2336

Magnetism and orbital physics of the Mott insulator LuVO3 M. Skoulatos

1, J.P. Goff

2, A. Kreyssig

3,4, J.-W. Kim

3, A.I. Goldman

3,4, M. Enderle

5, P. Freeman

5, A. Stunault

5, M.

Reehuis6, K. Habicht

6, S. Toth

6, L.D. Tung

7, Y. Joly

8, O. Zaharko

1, C. Rüegg

1 markos.skoulatos@psi.ch 1Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland, 2Department of Physics, Royal Holloway, Univ. of London, United Kingdom, 3Ames Laboratory US DOE, Iowa State University, USA, 4Department of Physics and Astronomy, Iowa State University, USA, 5Institut Laue–Langevin, Grenoble, France, 6Helmholtz Center Berlin for Materials and Energy, Germany, 7Department of Physics, Liverpool University, United Kingdom, 8Institut Néel CNRS-UJF, Grenoble, France

The interplay amongst the charge, spin, and orbital degrees of freedom and their phase transitions has attracted much attention recently in strongly correlated electron systems, particularly for the transition-metal (TM) oxides [1]. RVO3 vanadates (R = rare earth and Y) have 3d t2g bands at the Fermi level where the Jahn-Teller interaction is much weaker. As a result, the intrinsic frustration between spin and orbital degrees of freedom is believed to be crucial for understanding the interplay between different ordering mechanisms [2-4].

LuVO3 has two t2g electrons in V3+, adopting the high-spin configuration S = 1. One electron always occupies the dxy orbital due to the orthorhombic distortion, and the other one of two possible states, dyz or dzx. This can lead to a variety of orbital and magnetic orderings, which we were able to observe via resonant x-ray scattering (RXS) and polarised neutron scattering studies.

References

[1] M. Imada et al., Rev. Mod. Phys. 70, 1039 (1998) [2] P. Horsch et al., Phys. Rev. Lett. 91, 257203 (2003) [3] C. Ulrich et al., Phys. Rev. Lett. 91, 257202 (2003) [4] G. Khaliullin et al., Phys. Rev. Lett. 86, 3879 (2003)

The compound BaNi2(PO4)2 is well known to be a good prototype of quasi-2D planar antiferromagnet, whose structure consists of Ni2+ (S=1 ) ions located on a honeycomb lattice [1]. Below the Néel temperature TN≈23.6 K, the 3D magnetic ordering is antiferromagnetic and collinear, described by the propagation k=(0,0,0). The excitation spectrum displays two branches: a quasi-linear one associated with in-plane (IP) fluctuations and a gapped branch associated with out-of-plane (OP) fluctuations (energy gap of 2.8 meV). We have determined the temperature dependence of the OP-magnon lifetime in BaNi2(PO4)2 by measuring the neutron polarization decay with spin-echo time at different temperatures. The measurements were performed with improved version of the NRSE option ZETA recently installed on the CRG three-axis spectrometer IN22 at the ILL [2]. Our experimental results will be compared to recent theoretical calculations of the magnon damping for the classical 2D-XY antiferromagnetic system.

27

Measurement of neutron electric charge by the spin interferometry technique

V.V.Voronin, I.A.Kuznetsov

Petersburg Nuclear Physics Institute, 188350, Gatchina, Russia, vvv@pnpi.spb.ru

Neutron electric charge is an important parameter of modern physics. It can be a test of both Standard Moder (SM) and physics beyong the SM. The electric charge of the neutron is known to be zero to a rather high precision [1], but all attempts to improve the accuracy during the last two decades were unsuccessful. New method for checking neutron electroneutrality is proposed. The main idea of this experiment is to use the spin interferometry technique. Such technique is used in SESANS (Spin Echo Small Angle Neutron Scattering) installations. The SESANS technique provides a spatial splitting of neutron on two eigenstates with different projection of spin on magnetic field. After passing through the working area these two eigenstates are coupled back. So, the phase of the interference pattern, i.e. azimuthal spin direction, is defined by phase difference of two neutron eigenstates, accumulated in working area. If such system is placed into uniform electric field E, then two neutron eigenstates, due to their spatial splitting, will be under different electric potentials. With presence of electric charge of neutron qn it will give the energy splitting ΔEe=qn E Δz and, respectively, the phase shift Δφe=ΔEe τ/ћ, where Δz – value of spatial splitting, τ – time of staying of the neutron in electric field. So, one can see that such system is sensitive to neutron electric charge. Preliminary estimations show the using of technique mentioned above can improve the recent restriction on neutron electric charge [1] on two order of magnitude as minimum and it can reach the value better than σ(qn)~10

-23e.

References [1] Baumann, J., R. Gähler, J. Kalus, and W. Mampe, Phys. Rev. D (1988) 37 3107-3122.

Magnetic field profile and microscopic parameters of nonlocal superconductors*.

V. Kozhevnikov1, A. Suter

2, H. Fritzsche

3, V. Gladilin

4,5, M. Trekels

4, A. Volodin

4,

T. Prokscha2, E. Morenzoni

2, K. Temst

4, M. Van Bael

4, C. Van Haesendonck

4 and J. Indekeu

4

1 Tulsa Community College, Tulsa, OK, USA 2 Paul Scherrer Institute, Villigen, Switzerland

3 Canadian Neutron Beam Centre NRCC, Chalk River Laboratories, ON, Canada 4KU Leuven, Leuven, Belgium

5Universiteit Antwerpen, Antwerpen, Belgium One of the longest standing problems of experimental superconductivity is quantitative measurement of the in-depth distribution of the magnetic field penetrating into superconductors in the Meissner state. Such measurements, being important on their own, provide the most direct way to determine the London penetration depth, the key parameter whose absolute value is still not known for any superconductor. The theory predicts that in nonlocal superconductors the field profile is nonmonotonic with sign reversal at a certain depth. Knowledge of the field profile in such superconductors makes also possible to determine the Pippard coherence length and the phonon enhancement of effective mass of electrons near the Fermi surface. The measurements of such kind, for the first time performed with two extreme nonlocal superconductors (indium and tin) will be reported. The field profile was thoroughly measured using Low-Energy muon Spin Rotation spectroscopy and Polarized Neutron Reflectometry. Results of the measurements unambiguously confirm the nonlocal effect, first predicted by Pippard six decades ago. Obtained intrinsic parameters include the London penetration depth, the Pippard coherence length and the effective mass of the Cooper pairs. Application of the developed methodology to unconventional superconductors will be discussed as well. *Supported by NSF.

28

Session: Imaging

Chair: F. OTT

IMAGING OF MAGNETIC STRUCTURES WITH POLARISED NEUTRONS N. Kardjilov

1, A. Hilger

1, I. Manke

1, M. Strobl

2, G. Badurek

3, E. Jericha

3, J. Banhart

1

1. Helmholtz Centre Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany 2. European Spallation Source ESS AB, P.O. Box 176, SE-221 00 Lund, Sweden 3. Atominstitut, Vienna University of Technology, Stadionalee 2, 1020 Vienna, Austria

Owing to their zero net charge neutrons are able to pass through thick layers of matter (typically several centimeters), but are sensitive to magnetic fields due to their intrinsic magnetic moment. Therefore, in addition to the conventional attenuation contrast image, the magnetic field inside and around a sample can be visualized independently by detection of polarization changes in the transmitted beam [1]. This is based on the spatially resolved measurement of the cumulative precession angles of a collimated, polarized, monochromatic neutron beam that transmits a magnetic field [2]. The neutron imaging instrument CONRAD at HZB Berlin was equipped with solid state polarizing benders which were used to polarize and analyze a monochromatic neutron beam. The configuration was used for quantitative polarimetric experiments, where the polarization vector of the magnetic field associated with a sample was measured in three orthogonal directions. By applying an iterative algorithm to the measured rotation angles, it was possible to reconstruct the flux density of the 3D magnetic field that produced them. Polarizing filters based on polarized 3He gas were used for high resolution imaging of magnetic materials using polychromatic neutrons. Neutron depolarization imaging was used for observations of phase transitions between ferromagnetic and paramagnetic states in single crystals, allowing position-sensitive mapping of the Curie temperature [3]. Examples of investigation of various magnetic materials will be presented.

REFERENCES

[1] N. Kardjilov et al, Nature Physics 4, 399-403 (2008) [2] M. Dawson et al 2009 New J. Phys. 11 043013 [3] M. Schulz et al 2010 J. Phys.: Conf. Ser. 211 012025

29

Development of quantitative magnetic field imaging using time-of-flight neutron polarization analysis

T. Shinohara

1, K. Sakai

1, T. Kai

1, H. Hayashida

1, H. Sato

2, T. Negishi

2, M. Harada

1, M. Ooi

1,

K. Oikawa1, F. Maekawa

1, T. Oku

1, M. Arai

1, Y. Kiyanagi

2

1J-PARC Center, JAEA, Tokai, Ibaraki 319-1195, Japan, takenao.shinohara@j-parc.jp 2 Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan

Neutron imaging technique using polarized neutrons can be applicable to visualize the magnetic field distribution in the space or inside the materials. As the polarization change due to the neutron spin rotation, which is the results of the interaction between neutron spins and the magnetic field, depends on the neutron wavelength, analysis of wavelength dependence of the neutron polarization makes it possible to evaluate the magnetic field quantitatively. The usage of pulsed neutrons is very suitable for this technique, because their wavelengths can be determined easily and precisely by means of time-of-flight (TOF) method. In this work, we have been developing a quantitative magnetic field imaging technique by means of TOF polarization analysis using pulsed neutron beam at J-PARC. Recently, we have succeeded to obtain images of both the strength and the direction of magnetic field inside the solenoid coil or image of the magnetic domain structure in the soft magnetic foil. In addition, application of the polarimetry technique and three-dimensional analysis of the neutron polarization to the magnetic field imaging using TOF method have been also performed so as to map the spatial distribution of the magnetic field vector. In this paper, we report the details about our development and some results of magnetic field imaging using TOF-polarimetry technique.

Imaging Quantum Mechanical Effects in Superconductors with Polarized Neutrons

W. Treimer, O. Ebrahimi, N. Karakas

Beuth Hochschule Berlin, Department Physics, Mathematics & Chemistry, D-13353 Berlin, Germany, treimer@helmholtz-berlin.de and

Helmholtz Zentrum Berlin Wannsee, Dep. G-G1, Hahn-Meitner-Platz 1, D- 14109 Berlin, Germany Abstract Macroscopic Quantum effects such as the Meissner effect and magnetic flux trapping in massive Lead and Niobium samples could be visualized and quantified by radiography with polarized neutrons. A crystalline Pb sample expelled at T < Tc the external magnetic field Bext = 6.4mT, despite the rather large mosaic spread of 1.7° which suggested a certain flux trapping, but which was not observed. The polycrystalline Pb sample with the same purity (99.9999 weight%) showed only a partial Meissner effect and for Bext = 0 and T < Tc a non-uniform magnetic flux trapping. Based on radiographies with polarized neutrons the trapped and expelled magnetic fields could be calculated and 3D models produced. Niobium (SC type II) samples - different surface treated - suppressed nearly completely the Meissner effect and exhibit extremely non-uniform flux trapping for T<Tc and Bext = 0, both imaged with polarized neutrons. References [1] W. Treimer, O. Ebrahimi, N. Karakas, S. O .Seidel, Nuclear Inst. and Methods in Physics Research, A 651 (2011),

pp. 53-56; PONTO- An instrument for imaging with polarized neutrons [2] S Aull, O Ebrahimi, N Karakas, J Knobloch, O Kugeler, W Treimer Journ. of Phys., Conf. Series 340 (2012)

012001, p 1 - 7; Suppressed Meissner-effect in Niobium: Visualized with polarized neutron radiography [3] W. Treimer, O. Ebrahimi, N. Karakas, R. Prozorov, Phys. Rev. B (submitted) ; Polarized neutron imaging and 3D calculation of magnetic flux trapping in bulk of superconductors.

30

Multiple potential of TOF spin-echo induced spatial beam modulation (SEMSANS)

M. Strobl, J. Plomp, F. Wieder, C. Duif, N. Kardjilov, A. Hilger, A. Tremsin, I. Manke, W.G. Bouwman

ESS-AB P.O Box 176, SE-221 00 Lund, Sweden, markus.strobl@esss.se TUD RID, Mekelweg 15, NL-2629 JB Delft, Netherlands

HZB Hahan-Meitner Platz 1, 14109 Berlin, Germany Space Sciences Laboratory, University of California at Berkeley, Berkeley CA 94720, USA

Spatial beam modulation produced and resolved in a SESANS (spin-echo SANS) set-up has recently been introduced as a potential method for extending the range of SANS instruments into the ultra small angle regime [1]. In contrast to conventional SESANS, SEMSANS (spin echo modulation SANS) enables e.g. the investigation of magnetic samples and does not require any polarisation control in the sample region and thereafter. The precession field areas are set up such that the polarisation of neutrons depends only on their final position in the detector plane. Hence the use of a polarisation analyser provides a spatial modulation of intensity in the detector plane (SE-modulation) [2]. No significant beam collimation is required, while the resolution can be tuned by the geometry, the magnetic fields and the wavelength. Here we present on the one hand results of first proof-of-principle measurements using a reference sample, namely a solution of monodispersive polystyrene (PS-DVB) particles in D2O. On the other hand we introduce a grating based detection method overcoming the critical requirement of a high resolution detector. Additionally, ideas are presented to extend the applicable q-range of the method in a SANS instrument as well as its potential for application in neutron reflectometers and imaging instruments. In reflectometers the SEMSANS set-up might enable to measure specular and offspecular reflectivity independently as well as GISANS. In neutron imaging the method can be used for dark-field imaging [3] and has the potential to provide quantitative results concerning the identified structures beyond direct spatial image resolution, i.e. spatially resolved SANS without scanning. First results achieved with a time-of-flight set-up prove the feasibility of the method at spallation sources and due to the moderate wavelength resolution required a long pulse source like planned for the European Spallation Source (ESS) is preferable. References [1] W.Bouman et al. Phys B 2011 [2] W. Bouwman et al. NIMA 2010 [3] M. Strobl et al. PRL 2008

31

Session: Facilities News

Chair: A GUKASOV

Design of VIN ROSE at BL06 beam line in J-PARC/MLF Masahiro Hino, Tatsuro Oda

1, Norifumi L Yamada

2, Masaaki Kitaguchi, Hidenori Sagehashi

2,

Yuji Kawabata and Hideki Seto2

Research Reactor Institute, Kyoto university(KURRI), Kumatori,Osaka,590-0494, Japan, hino@rri.kyoto-u.ac.jp

1Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan 2Neutron Science Laboratory, High Energy Accelerator Research Organization (KEK), Tokai, Ibaraki 319-1106, Japan

KEK and Kyoto University started to construct new beam line for VIN ROSE (VIllage of Neutron ResOnance Spin Echo spectrometers) at BL06 J-PARC/MLF from FY 2011. The VIN ROSE consists of two spectrometers, MIEZE (Modulated IntEnsity by Zero Effort) and NRSE (Neutron Resonance Spin Echo) [1,2] with wide time domain from 1ps to 100 ns. They have been developed at C3-1-2-2(MINE1) beam line at JRR-3 reactor by KURRI group. We also have tested TOF-MIEZE spectroscopy at BL10 (NOBORU) beam line at J-PARC and mathematically described TOF-MIEZE spectroscopy. The experimental result was well reproduced by the description. The advantage of MIEZE is flexible sample environment and polarimetry analysis. The key device of NRSE is focusing mirror and high-m polarizing device and NRSE is dedicated for small sample size. Both spectrometers are to use intensity gain of J-PARC with high S/N. In this study, we will show design of the VIN ROSE and current status of the BL06 beam line at J-PARC. References [1] R. Golub and R. Gaehler, Z Phys.B65(1987) 269. [2] R. Gaehler, R. Golub and T. Keller, Physica B 180-181(1992) 899.

CAP2015 : program of renovation of the instruments at the LLB

A. Menelle, J.P. Visticot

Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette, France Alain.menelle@cea.fr

The program of renovation of the instruments of the LLB is going on. Within a few years, more the half of our 22 spectrometers will be renovated. 6 of them have already been completed, mostly in the diffraction field, and are open or will be open soon to users. In total, all types of instruments are concerned. A detailed overview of this program will be presented with the current status of each project. New experimental capabilities opened by the gains obtained in the efficiency of the spectrometers will be shown.

32

Polarizing neutron optics from Helmholtz-Zentrum Berlin Th. Krist, J.-E. Hoffmann

Helmholtz-Zentrum Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany krist@helmholtz-berlin.de

In the last years a variety of polarizing neutron optical devices has been developed at HZB, mainly solid state elements where the neutrons are transported in thin silicon wafers with coated walls. We show results of solid state polarising benders, solid state collimators with polarizing walls and a solid state radial bender for the polarisation analysis of neutrons over an angular range of 3.8 deg. Another device consists of a solid state polarising bender without absorbing layers used together with a collimator, which allows polarizing or analyzing neutrons without deflecting them from their original direction. Two-dimensional polarisation analysers for an angular range of 5 degrees in both directions are presented. A polarizing cavity in a guide with a cross section of 60mm x 100mm was built which polarizes neutrons with wavelengths above 0.25nm. In all these polarizing devices polarisations of 95% were realised. Recently a polarizing S-bender with a cross section of 30mm x 100mm was tested, showing at a wavelength of 4.4Å a polarization above 98% and a transmission above 65%.

New polarised neutron opportunities at the upgraded three-axis spectrometer FLEXX

K. Habicht1, F. Groitl

2, M.D. Le

2, D.L. Quintero-Castro

2, M. Skoulatos

2,3, R. Toft-Petersen

2

1Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany, habicht@helmholtz-berlin.de

2 Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany 2 present address: Paul Scherrer Institute, 5232 Villigen PSI, Switzerland

The cold triple axis spectrometer FLEX has had a very successful 15 years of user operations exploiting extreme sample environment in addition to serving as a platform for the development of the neutron resonance spin echo (NRSE) technique. Recently, the primary spectrometer of FLEXX was upgraded with new m=3 guides and a new velocity selector to remove higher order scattering, eliminating the need for filters. A polarising S-bender can be vertically moved into the primary beam path for optional use. The following neutron optical components, a converging elliptical section to focus neutrons onto a virtual source, an optional collimator changer and a vertical neutron guide, are equipped with permanent magnet guide fields while the guide field at the new double focussing monochromator is provided by a pair of Helmholtz coils. The upgrade, aiming at an increase in polarised neutron flux at the sample, will benefit both XYZ polarised neutron work at FLEXX and its currently upgraded NRSE option. The new NRSE arms will give access to higher scattering angles convenient for Larmor diffraction. The accepted beam width is increased due to the new design of the NRSE coils. In addition larger achievable coil tilt angles enable measurements of steeper dispersions. We shall present first results from the new instrument and assess the actual improvements for polarised neutron work at FLEXX.

33

A New Polarized Neutron Reflectometer (SHARAKU) at the Intense Pulsed Neutron Source

of the Materials and Life Science Experimental Facility of J-PARC

TAKEDA Masayasu1,2,3

, YAMAZAKI Dai1,2

, SOYAMA Kazuhiko1,2,3

, MARUYAMA Ryuji2, HAYASHIDA Hirotoshi

2, ASAOKA

Hidehito1,2,5

, YAMAZAKI Tatsuya1, KUBOTA Masato

1,2, AIZAWA Kazuya

2, ARAI Masatoshi

2, INAMURA Yasuhiro

2, ITOH

Takayoshi4, KANEKO Koji

1,2,3, MIZUSAWA Mari

4, NAKAMURA Tatsuya

2, NAKATANI Takeshi

2, OIKAWA Kenichi

2,

OHHARA Takashi4, SAKAGUCHI Yoshifumi

4, SAKASAI Kaoru

2, SHINOHARA Takenao

2, SUZUKI Junichi

4, SUZUYA

Kentaro2, TAMURA Itaru

2,3, TOH Kentaro

2, YAMAGISHI Hideshi

2, YOSHIDA Noboru

4, and HIRANO Tatsumi

6

1Quantum Beam Science Directorate, Japan Atomic Energy Agency(JAEA), Tokai, Ibaraki 319-1195, Japan, takeda.masayasu@jaea.go.jp

2J-PARC Center, Tokai, Ibaraki 319-1195, Japan, 3Department of Research Reactor and Tandem Accelerator, JAEA, Tokai, Ibaraki 319-1195, Japan, 4Research Center for Neutron Science and Technology, Comprehensive Research

Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan, 5Advanced Science Research Center, JAEA, Tokai, Ibaraki 319-1195, Japan, 6Hitachi Research Laboratory, Hitachi Ltd., Hitachi, Ibaraki 319-1292, Japan.

A new polarized neutron reflectometer with vertical sample-plane geometry has been installed at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). The user program of this reflectometer has been already started in February 2012 although it is still at the early commissioning stage. At the conference, the outline design specification, and the basic performance of this reflectometer will be presented. Reference http://j-parc.jp/researcher/MatLife/en/instrumentation/ns_spec.html#bl17

Up-Coming Polarised Neutron Capabilities on ANSTO Instruments Using Polarised 3He Neutron Spin Filters

G. McIntyre, Wai Tung Lee

1, Frank Klose

1, David Jullien

2, Pierre Courtois

2, Ken Andersen

3

1Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, wtl@ansto.gov.au 2Institute Laue Langevin, Grenoble, France

3European Spallation Source, Lund, Sweden A joint project of the ANSTO and the ILL is underway to put Polarised 3He based neutron spin-filters - polariser and polarization analyser on 6 ANSTO instruments. The instruments include SANS Quokka, diffractometer Wombat, reflectometer Platypus, thermal and cold triple-axis spectrometers Taipan and Sika, and cold neutron time-of-flight spectrometer Pelican. Works are underway to expand their use to Laue diffractometer Koala and new instruments that are being designed and built. A 3He gas polarizing station based on the Metastable Exchange Optical Pumping method [1] is being shipped to ANSTO. It has reached 72% 3He polarization in spin-filter cell at a 1.2 bar-litre production rate. Silicon-window cells with 3He decay time constant T1 up to 300 hours are being incorporated into several instruments. Wide-angle analyser “Pastis” cells [2] will analyse the scattering on the diffractometer and the TOF spectrometer. To house the 3He cells, our works has produced 500mm-long magnetio-static cavities “Magic Boxes” (MB) with T1(MB-only)=400 hours, and “Pastis” uniform field coil with T1(coil-only)=400-1200 hours. We will present the latest development of the project. References [1] G.K. Walters, et al., Phys. Rev. Lett. 8 (1962) 429. [2] K.H. Andersen, et al., Physica B404 (2009) 2652.

34

Current status of the polarized 3He R&D work at SNS

Xin Tong, Chenyang Jiang, Dan Brown, Wai-Tung Hal Lee, Lee Robertson

Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA, tongx@ornl.gov Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia

We report the current status of polarized 3He R&D work at SNS which includes cell fabrication system, local pumping system, in-situ polarized 3He pumping system and polarized gas transfer system. We will focus on the in-sitiu pumping system. The upgraded in-situ polarized 3He pumping system developed for the Magnetism Reflectometer at the Spallation Neutron Source (SNS). Unpolarized neutron transmission shows that 77% of 3He polarization achieved and maintained over 3 day experiment period. Polarized neutron transmission measurement show that the analyzing efficiency of the system is >99% at 3-5A; flipping ratio of 100 for 2.5A neutron were achieved. The average transmission is 25% for 2-5A polarized neutrons. Full polarization analysis on a reference sample (Fe/Cr GMR ML) showing a strong magnetic off-specular scattering will be presented. The setup is certified as class 1 laser environment and is commissioning for users.

Development of a compact laser optics system for an in-situ SEOP 3He neutron spin filter

T. Oku

1), H. Kira

2), K. Sakai

1), T. Shinohara

1), Y. Sakaguchi

2), T. Ino

3), Y. Arimoto

3),

K. Ohoyama4)

, H. Hiraka4)

, L.J. Chang5)

, M. Nakamura1)

, J. Suzuki2)

, H.M. Shimizu6)

, M. Arai1)

, Y. Endoh1)

, K. Kakurai

1)

1)JAEA, Tokai, Ibaraki 319-1195, Japan, oku.takayuki@jaea.go.jp, 2)CROSS, Tokai, Ibaraki 319-1106, Japan, 3)KEK, Tsukuba, Ibaraki 305-0801, Japan, 4)IMR, Tohoku University, Sendai, Miyagi 980-8577, Japan, 5) National Cheng

Kung University 70101, Taiwan, 6)Nagoya Univ., Furocho, Chikusa, Nagoya 464-8602, Japan We have been developing an in-situ SEOP polarized 3He neutron spin filter to apply it to pulsed neutron experiments. The 3He based neutron polarizer is useful in experiments such as polarized neutron scattering experiments in a wide q-range, inelastic scattering experiment with high energy magnetic and phonon excitation, magnetic field imaging and etc, since it is effective for neutrons in a wide energy range. To introduce the in-situ SEOP polarized 3He neutron spin filter into the instruments of the pulsed neutron facility such as J-PARC, it is important to make the system compact and stable, because the system is located inside thick and bulky radiation shields for high energy gamma ray and neutrons. In this study, we have developed a compact laser optics system with a volume holographic grating (VHG) element for the SEOP system. We report the design of our spin filter system and some results of the 3He polarizing experiments in this paper.

Fig. 1 Schematic layout of our laser optics.

35

Wednesday, July 4th 2012

Session: Thin films and nanomagnets

Chair: B. Gillon

Spin Densities in Molecule-Based Magnets: Understanding Magnetic Interaction Mechanisms

F. Palacioa, J. Luzón

a,b, J. Campo

a, A. Millán

a, G.J. McIntyre

b and J.M. Rawson

c

a Material Science Institute of Aragón (CSIC-University of Zaragoza), 50009 Zaragoza (Spain) b Institut Max von Laue - Paul Langevin, 6 Jules Horowitz, 38042 Grenoble (France)

c Dept. of Chemistry. University of Windsor. N9B 3P4 Windsor Ontário (Canadá) Magnetic interactions in molecular magnets are strongly influenced by the spin density distribution in the molecules, as spin delocalization and spin polarization strongly affects exchange interactions. The aim of this work is to exemplify such influence through the analysis of the experimental and computational determination of the spin density distribution and the magnetic coupling constants of two kind of magnetic molecular materials: the series of 3D antiferromagnets of general formula A2FeX5•H2O (A=alkali or NH4, X=Cl, Br) and the thiazyl-based magnets p-X-C6F4CNSSN•. Although the A2FeX5•H2O series of antiferromagnets has been extensively studied as model examples of crossover dimensionality in Heisenberg lattices (R.L. Carlin 1985), an open question still remained: why are their transition temperatures so relatively high considering that their super-exchange pathways are of the type Fe − X · · ·X − Fe or Fe − O · · ·X − Fe? (Campo 2008, Luzón 2008) The dithiadiazolyl radical family include the purely organic magnet with the highest known transition temperature and the organic ferromagnet with the second highest ordering temperature. In this presentation we analise the magnetic interaction mechanisms via the spin density determinations and fundament the strong magnetic differences found among family elements (Rawson 2005). References R.L. Carlin and F. Palacio, Coord. Chem. Rev., 65, 141-165 (1985). J. Campo, J. Luzón, F. Palacio, G. J. McIntyre, A. Millán, A. R. Wildes, Phys Rev B. 78, 054415 (2008) J. Luzón, J. Campo, F. Palacio, G. J. McIntyre, A. Millán, Phys Rev B. 78, 054414 (2008) J.M. Rawson, J. Luzon and F. Palacio, Coord. Chem. Rev., 249, 2631-41 (2005).

36

Joint charge and spin densities refinement

Maxime Deutscha, Nicolas Claisera, Maria-Angels Carvajalb Claude Lecomtea

, Béatrice Gillonc, Jean-Michel

Gilletd, Dominique Luneau

e and Mohamed Souhassou

a

aLaboratoire CRM2, (UMR UHP-CNRS 7036), Institut Jean Barriol, Université de lorraine, Vandoeuvre-lès-Nancy (France).E-mail: Maxime.deutsch@crm2.uhp-nancy.fr

bDepartament de Quimica Fisica i Inorganica, Universitat Rovira i Virgili Tarragona, (Spain)

cLaboratoire Léon Brillouin (CEA-CNRS), Centre d'Etudes de Saclay (France). dLaboratoire SPMS, Ecole centrale de Paris, grande voie des vignes, Chatenay malabry (France)

e Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Lyon-1, (France)

A new charge and spin density model and the corresponding refinement software was recently developed to combine X-ray and polarized neutron diffraction experiments [1,2]. This joint refinement procedure allows getting access to both the charge and spin densities but also to spin up () and spin down () electron distributions. These two quantities (and ) modelled experimentally for the first time enable for a further comparison with theoretical models. The presentation will focus on the refinement procedure and its application to the case of an end-to-end azido double bridged copper(II) complex[3,4]. The results of this joint refinement of X-ray and polarized neutron diffraction data will be presented and compared to the theoretical densities. [1] Souhassou, M., Deutsch, M., Claiser, N., Pillet, S., Ciumacov, Y., Becker, P. J., Gillon, B., Gillet, J.-M. and Lecomte, C. Acta Cryst. A, to be submitted. [2] Lecomte C., Deutsch M., Souhassou M., Claiser N., Pillet S., Becker P., Gillet J.-M., Gillon B. and Luneau D., ACA Transactions (2011). [3] Aronica, C., Jeanneau, E., El Moll, H., Luneau, D., Gillon, B., Goujon, A., Cousson, A., Carvajal, M. A., and Robert, V. Chem. Eur. J. 13(13), 3666–3674 (2007). [4] Deutsch, M., Carvajal, M.-A., Claiser, N., Lecomte, C., Gillon, B., Gillet, J.-M., Luneau D. and Souhassou, M. to be submitted

Polarized Neutron Diffraction and molecular magnetic anisotropy: the local susceptibility tensor approach

Dominique Luneau, Ana Borta, Olga Iasco, Béatrice Gillon, Arsen Gukasov, Karl Ridier Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Lyon 1 (France)

Laboratoire Léon Brillouin (CEA-CNRS), Centre d'Etudes de Saclay (France).

PND has proved to be particularly suitable for the study of magnetic molecular compounds and the determination of the spin density. This provides unique information on the paths of magnetic interactions and the nature of magnetic intra-or intermolecular coupling [1-4]. In this paper we show on recent examples how we can go beyond the spin density reconstruction and use the local susceptibility tensor approach to study the magnetic anisotropy in such compounds [5, 6]. The aim is to get some relationships between the magnetic anisotropy and the structure that are missing in the research field of single-molecule magnets (SMM).

References [1] R. Caciuffo, O. Francescangeli, L. Greci, S. Melone, B. Gillon, Physica B 1992, 180-181, 76-78. [2] E. Ressouche, J. Boucherle, B. Gillon, P. Rey, J. Schweizer, J. Am. Chem. Soc.1993, 115, 3610-3617. [3] B. Gillon, C. Mathonière, E. Ruiz, S. Alvarez, et al. J. Am.Chem. Soc., 2002, 124(48), 14433–14441 [4] C. Aronica, E. Jeanneau, H. El Moll, D. Luneau, B. Gillon, et al., Chem. Eur. J., 2007, 13, 3666-3674 [5] A. Gukasov and P. J. Brown, J. Phys-Condens. Mat. 2002, 14, 8831-8839. [6] A. Borta, B. Gillon, A. Gukasov, A. Cousson, D. Luneau, E. Jeanneau, I. Ciumacov, H. Sakiyama, K. Tone and M. Mikuriya, Phys. Rev. B 2011, 83.

37

Source of magnetic anisotropy in a soft layered magnet WCuT

O. Zaharko, W. Wallace, M. Pregelj, A. Zorko, A. Goukassov, S. Klokishner, R. Podgajny

Laboratory for Neutron Scattering, Paul Scherrer Institute, 5232 Villigen, Switzerland, Oksana.Zaharko@psi.ch Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia

Laboratoire Léon Brillouin, CEA/Saclay, France Institute of Applied Physics, Academy of Sciences of Moldova, 2028 Kishinev, Moldova

Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland

We aim to distinguish the origin of magnetic anisotropy in the quasi-two-dimensional (2D) copper-octacyanotungstenate Cu4(tetrenH5)[W(CN)8]47.2H2On, (WCuT) [1], which has been recently identified as a 2D magnetic system [2, 3] with the Berezinski-Kosterlitz-Thouless transition at Tc=33 K and a spin-flip transition at H||b ≤ 100 G. From experimental single crystal neutron flipping ratios and EPR spectra we find significant anisotropy of the W5+ susceptibility tensor (while susceptibility tensor of Cu2+ remains isotropic) and strong in-plane anisotropy below 45 K. Calculations show that the common action of crystal field and spin-orbit coupling lead to anisotropic magnetic single-ion properties of the W+5 ion, however, the effective exchange Hamiltonian of a Cu-W pair is within the first approximation isotropic. We proceed with verification of the origin of magnetic anisotropy considering exchange anisotropy and higher order contributions in the exchange Hamiltonian. References [1] R. Podgajny, T. Korzeniak, M. Bałanda et al. Chem. Commun. 1 (2002) 1138. [2] F. L. Pratt, P. M. Zielinski, M. Bałanda et al. J. Phys. Condens. Matter 19 (2007) 456208. [3] M. Bałanda, R. Pełka, T. Wasiutyński et al. Phys. Rev. B 78 (2008) 174409.

USANSPOL studies of the microstructure of magnetic ribbons

E. Jericha

1, G. Badurek

1, C. Gösselsberger

1, R. Grössinger

2, D. Süss

2

1Vienna University of Technology, Atominstitut, Wien, Austria, jericha@ati.ac.at 2Vienna University of Technology, Institute of Solid-State Physics, Wien, Austria

Amorphous magnetic ribbons represent both novel technologically relevant complex samples which are currently in the process of material development for use as magnetic sensors and actuators due to their exceptional magnetostriction properties as well as illustrative examples for developing the technique of ultra-small-angle polarised neutron scattering (USANSPOL). This method was described in some detail in Ref. [1] for the study of magnetic microstructure. We present experimental results on a variety of magnetic ribbons under various environmental conditions, including zero-field environment, the influence of external magnetic field, mechanically induced stress, or a combination of both effects, and in magnetically saturated state. Measurement results allow an assessment of the native sample state which may exhibit form anisotropy due to a special manufacturing process. A two-dimensional record of the scattered neutron intensity is essential for non-isotropic structures. At the other end of the internal length scale, we observe the sample under saturation conditions from which we may distinguish crystalline and amorphous states on a microstructure level with implications on the applicability. The evolution of the magnetic structure between these two endpoints is seen from experiments with applied external magnetic field or mechanical stress of varying strength and can be followed up to the resolution limit of the technique. References [1] E. Jericha, G. Badurek, C. Gösselsberger, D. Süss, J. Phys. Conf. Ser. 340 (2011) 012028. Experimental and methodic progress in ultra-small-angle polarised neutron scattering on novel magnetic materials.

38

Magnetic neutron scattering on nanomagnets: Decrypting cross-section images using micromagnetic

simulations

Andreas Michels1, Sergey Erokhin

2, Dmitry Berkov

2, Natalia Gorn

2

1University of Luxembourg, andreas.michels@uni.lu 2INNOVENT Technology Development, Jena, Germany

We have used numerical micromagnetics for the calculation of the magnetic small-angle neutron scattering (SANS) cross section dΣM/dΩ of two-phase nanocomposites. In contrast to neutron experiments, in which one generally measures only a weighted sum of the Fourier components of the magnetization, our approach allows one to study the behavior of the individual contributions to dΣM/dΩ. Results for the unpolarized SANS cross section as well as for the spin-flip SANS will be discussed. The procedure furnishes unique and fundamental information regarding the magnetic microstructure and corresponding magnetic scattering from nanomagnets. In particular, our simulations explain the recent observation of magnetodipolar correlations in two-phase nanocomposites and, moreover, suggest their relevance for a wide range of magnetic materials such as nanocomposites, nanoporous magnets, and magnetic recording media. References [1] S. Erokhin, D. Berkov, N. Gorn, and A. Michels, Phys. Rev. B 85 (2012) 024410. Micromagnetic modeling and small-angle neutron scattering characterization of magnetic nanocomposites. [2] S. Erokhin, D. Berkov, N. Gorn, and A. Michels, Phys. Rev. B 85 (2012) in press. Magnetic neutron scattering on nanocomposites: Decrypting cross-section images using micromagnetic simulations.

Disrupting Interparticle Magnetic Cross-Talk within Fe3O4 Nanocubes Using FePt Inclusions

K. L. Krycka

1, C. H. Lai

2, B. J. Kirby

1, C. L. Dennis

1, and J. A. Borchers

1

1NIST Center for Neutron Research, Gaithersburg, MD, US, kathryn.krycka@nist.gov

2National Tsing Hua University, Dept. of Materials Science and Engineering, Hsinchu, Taiwan Biocompatible Fe3O4 nanocubes are highly promising for their use as MRI T2 contrast agents. 16.1 nm cubes of Fe3O4 (Sample A) produce a resistivity of 194 mM-1s-1 at 4.7 T, which is larger than commercially available Resovist®. This can be improved even further to 360 mM-1s-1 at 4.7 T by using 14.7 nm Fe3O4 nanocubes with 4.1 diameter FePt inclusions (Sample B). Polarization-analyzed small-angle scattering is ideal for detecting the underlying differences in magnetic morphology [1] and magnetic cross-talk between these nanoparticle types. This technique revealed that in powder form Samples A and B saturate to similar magnetic values less than that of bulk Fe3O4 at 1.2 Tesla. Yet when the field is relaxed to 0.005 Tesla, the nanocubes form magnetic domains of 27.5 + 1 nm (> single particle) for Sample A and 16 + 1 nm (~ 1 nanoparticle) for Sample B. Similarly, when the nanocubes were solvated to 5 mg/ml in D2O (to minimize the Fe3O4 structural scattering via contrast matching and enhance the relative magnetic contribution) both samples displayed a percolation network-like of cubes distributed throughout the solution, yet only Sample A showed multi-particle magnetic domains of approximately 5-7 nanocubes in length. We speculate that the primary function of the FePt is to disrupt the formation of long-range magnetic domains. In turn, this could explain the increased magnetic relaxation that is observed as a function of decreasing applied magnetic field. References [1] K.L. Krycka, R.A. Booth, C.R. Hogg, Y. Ijiri, J.A. Borchers, W.C. Chen, S.M. Watson, M. Laver, T.R. Gentile, L.R. Dedon, S. Harris, J.J. Rhyne, and S.A. Majetich, Phys. Rev. Lett. 104 (2010) 207203 Core-Shell Magnetic Morphology of Structurally Uniform Magnetite Nanoparticles.

39

Controlled interfaces for novel physical phenomena and functionality: Interface-induced ferromagnetism at

paramagnetic/antiferromagnetic perovskite films

Valeria Lauter1, Hans Christen

2, 3, Haile Ambaye

4, Mike Biegalski

2, Steven Nagler

1

1 Quantum Condenced Matter Division, ORNL, Oak Ridge, TN, USA, lauterv@ornl.gov 2Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, USA

3Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA 4Research Accelerate Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6393, USA

Epitaxial LaMnO3 films grown on SrTiO3 substrates show that “interface doping” or “charge transfer” can induce magnetism at interfaces. Our own recent work on LaMnO3/SrTiO3 interfaces demonstrated that the precise nature of the interface determines its magnetic structure - with the MnO2-SrO interface showing a different magnetization than the LaO-TiO2 interface. To investigate interfacial structures, we used polarized neutron reflectometry (PNR) with off-specular scattering. PNR reveals the magnetization profile across a film with a spatial resolution better than 0.5 nm in the direction perpendicular to the interfaces. Magnetization distribution in LaMnO3 film is not uniform and is enhanced towards the interfaces. All interfaces show an enhancement, but its magnitude and length scale depends on the interface termination. Our results give evidence of reversible temperature- and field- dependent structural changes in LaMnO3 film which undergo a phase transition. We determined that a structural phase transition in SrTiO3 and the misfit strain trigger appearance of twins to reduce stresses and to adjust lattice mismatch between the film and the substrate. We show that a laterally correlated superstructure appearsdue to interaction of structural modifications with the magnetization the film. The PNR experiments were performed using the Magnetism Reflectometer at Spallation Neutron Source, Oak Ridge National Laboratory (ORNL). Research at ORNL was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy.

MAGNETIC LAYER IN A NEUTRON WAVE RESONATOR

Yu.V. Nikitenko

FLNP, JINR, 141980 Dubna, Moscow region, Russia

Expressions are received for neutron density and neutron reflection and transmission amplitudes in case of the non-collinear magnetic layer in the static and rotating magnetic fields placed inside of the neutron wave resonator. It is shown the enhancement of the spin-flip reflection intensity and density of neutrons in opposite to initial spin state are enhanced in second and third degree relatively of enhancement of neutron density in the initial spin state, correspondently. Conditions are defined for high sensitive measurements of the magnetic layer parameters.

40

RF field stimulated magnetization kinetics probed in thin films with MIEZE based Time-Resolved AC (TRAC) PNR

Kirill Zhernenkov

1, Dmitry Gorkov

1, Hartmut Zabel

1, Boris P Toperverg

1

Nicolas Martin2, Louis-Pierre Regnault

2

Ruhr-Universität Bochum Bochum, 44780, Bochum Germany, v-zherne@ill.fr

CEA Grenoble INAC-SPSMS-MDN, 38054, Grenoble, France Since many decades response of magnetization on magnetic fields was thoroughly studied in different systems, e.g. thin continuous and laterally patterned films and multilayes, applying various experimental techniques [1]. However, in recent years much attention is paid to the study of dynamic processes under the influence of alternating magnetic fields. One of the important tasks is the determination of the re-magnetization regimes and the role of e.g. different terms in the Landau Lifshits equation (LLE) over a broad frequency range. This task can be approached with Time-Resolve AC (TRAC) Polarized Neutron Reflectometry (PNR) which records a time evolution of the depth resolved magnetization profile in the sample subjected to AC field. Due to uncertainties in the neutron flight-path, wavelength spread, etc. this “brute force” method applies at relatively low AC frequencies. However, the time modulation of the incident beam provided with the MIEZE sep up solves the problem and substantially increases the applicability range of TRAC PNR. The latter, gives a unique access to the frequency dispersion of longitudinal and transverse components of the retarded non-linear response function of the system. The experimental data were collected from thin Fe film placed in crossed DC and AC magnetic fields in a 40-350KHz frequency range. It is shown that at low frequencies the net magnetization adiabatically follows the AC field. At higher frequencies the damping starts to play a role. References [1] M.R. Fitzsimmons, S.Bader, J. Borchers, G. Felcher , Furdyna J, A. Hoffmann, J. Kortright, I. Schuller, T. Schulthess, S. Sinha, M. Toney, D. Weller, D. Wolf J. Magn.Magn. Mater. 271 (2004) 103

41

Session: Soft Matter

Chair: S. Longeville

Neutron spin echo revealed thickness fluctuations in surfactant membranes

Michihiro Nagao

Center for Exploration of Energy and Matter, Indiana University and NIST Center for Neutron Research, mnagao@indiana.edu

Polarized neutrons are successfully applied to obtain high energy resolution quasi-elastic neutron scattering spectroscopy in the neutron spin echo (NSE) technique. Recently NSE revealed dynamical processes in a surfactant membrane system on a length scale near the membrane thickness where the classical elastic membrane model breaks down. This excess dynamic (on top of the bending fluctuations) was observed in a nonionic surfactant, water and alkane system, and was attributed to thickness fluctuations of the membrane. The fluctuation amplitude was estimated to be a few angstroms and part of the work was well reproduced by molecular dynamics simulations [1-3]. Further investigations of such thickness fluctuations are ongoing in lipid bilayer vesicles. Lipid bilayers have been considered as model biological membranes and have been used widely to investigate physical and chemical properties of the membranes. Evidence of thickness fluctuations above the melting transition temperature, Tm where the lipid tails are in fluid phase, is observed, while fluctuations are not discernable below Tm. The estimated amplitude of the observed membrane thickness fluctuations is approximately 4 Å, which is consistent with theoretical expectations and molecular dynamics simulations [4]. References [1] M. Nagao, Physical Review E 80 (2009) 031606. [2] M. Nagao, S. Chawang, T. Hawa, Soft Matter 7 (2011) 6598. [3] M. Nagao, Journal of Chemical Physics 135 (2011) 074704. [4] A.C. Woodka, P.D. Butler, L. Porcar, B. Farago, M. Nagao, submitted.

Polarized neutron in structural biology – present and future outlook

J.K. Zhao, NIS-Division, Oak Ridge National Laboratory. MS 6475, rm B464, Bldg 8600, Oak Ridge National Lab. Oak Ridge, TN, 37830. zhaoj@ornl.gov

Hydrogen has a strong polarization-dependent neutron scattering cross section. This property has been exploited in the study of soft matters, especially biological macromolecules. When a polarized neutron beam is scattered off a polarized hydrogenous sample, the otherwise large hydrogen incoherent cross section is drastically reduced while the coherent signal is significantly increased. Past experiments have demonstrated the potentials and benefits of polarized neutron scattering from soft materials. The main technical challenge of polarized neutron scattering from biological matters lies at sample polarization. Dynamic nuclear polarization is a proven yet rather sophisticated technique. Its complexity is one of the main reasons for the technique's slow adoption. The future of polarized neutron scattering in biology may rest largely in neutron protein crystallography. Polarization of protein crystals is much easier to accomplish, since protein crystals are typically rather small (<<1mm) and only require small and easy- to-operate polarization apparatuses. In addition, the high resolution nature of neutron protein crystallography means that we will be able to study individual atoms using the polarized neutron scattering technique.

42

Spin Contrast Variation Study of Fuel-efficient Tire Rubber

Yohei Noda

1, Daisuke Yamaguchi

1, Takeji Hashimoto

1, Shin-ichi Shamoto

1,

Satoshi Koizumi2, Takeshi Yuasa

3, Tetsuo Tominaga

3, and Takuo Sone

3

1 Japan Atomic Enegy Agency, Ibaraki 319-1195, JAPAN, noda.yohei@jaea.go.jp 2 Ibaraki University, Ibaraki 316-8511, JAPAN, 3 JSR Corporation,Mie 510-8552, JAPAN,

After the pioneering works of Stuhrmann (GKSS) and van den Brandt (PSI), we have developed a spin contrast variation technique. Our target is hydrogeneous solid materials such as polymer or rubber, which are not easy to deuterate and can absorb a vapor of a stable free radical, TEMPO, which serves as an electron spin source necessary for high proton spin polarization (P) through dynamic nuclear polarization [1, 2]. By use of this vapor permeation technique, we succeeded in polarizing silica-filled SBR rubber, which is a material for fuel-efficient tire (Fig. 1). From the SANS profiles against a polarized neutron beam (λ=6.5Å, |Pneutron|=98.5 %) with various P values, we succeeded in separating the partial scattering function of silica, which is considered to be a key factor for the fuel-efficiency. References [1] Y. Noda, Takayuki Kumada, Takeji Hashimoto, Satoshi Koizumi, Physica B 404 (2009) 2572. [2] Y. Noda, Takayuki Kumada, Takeji Hashimoto, Satoshi Koizumi, Journal of Applied Crystallography 44 (2011) 503.

Polarization Analysis using 3He for incoherent background reduction in SANS

Earl Babcock, Sahir Zahli, Alexander Ioffe

Jülich Centre for Neutron Science, Lichtenberg str. 1, 85747 Garching GERMANY In soft matter SANS studies, especially at large Q range, incoherent scattering becomes the dominant signal. The incoherent contribution can be orders of magnitude larger than the coherent signal of interest; even after the total signal from the solvent is subtracted. This is an intrinsic problem because this remaining incoherent signal comes from the sample itself and obscures the desired structural information. Polarization analysis has the potential to fully separate the coherent signal and make analysis of difficult samples more certain. However because of inelastic scattering one must be very careful to correctly perform the polarization and detector efficiency corrections. Without such corrections one an increase in the fidelity of the coherent signal, however in order to surpass the typical levels of statistical errors for such measurements at the largest Q range, corrections should be taken into account. This paper will address the issues associated with the correct separation of coherent and incoherent scattering for soft matter samples and propose and describe a method of implementation using a continuously polarized 3He spin filter currently under development.

Fig. 1 SANS profile of fuel-efficient tire rubber, which depends on

proton spin polarization (P).

43

Dynamically Polarised Proton Spins as a Tool to Tune the Scattering Cross Section in Neutron Laue Diffraction

F.M. Piegsa

1,2, M. Karlsson

3,4, B. van den Brandt

5, C.J. Carlile

3, E.M. Forgan

6,

P. Hautle5, J.A. Konter

5, G.J. McIntyre

2,7, and O. Zimmer

2

1ETH Zürich, Institute for Particle Physics, CH-8093 Zürich, Switzerland 2Institut Laue-Langevin, BP 156, F-38042 Grenoble, France

3European Spallation Source ESS AB, P.O. Box 176, SE-221 00, Lund, Sweden 4Department of Applied Physics, Chalmers University of Technology, S-41296 Göteborg, Sweden

5Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 6School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK

7ANSTO, Locked Bag 2001, Kirrawee DC NSW 2232, Australia Neutron diffraction on samples with large hydrogen content, e.g. protein crystals, generally suffers from a strong featureless background due to incoherent scattering by the protons. The incoherent scattering arises because the proton spins are normally completely disordered, and the scattering length depends strongly on the relative orientation of proton and neutron spins. Here, we report on a polarised neutron Laue diffraction experiment on a single crystal of lanthanum magnesium nitrate hydrate. The experiment was carried out at the FUNSPIN beam line at the continuous spallation neutron source SINQ (PSI). It demonstrates that the intensity of the Laue reflections can be enhanced or diminished significantly, while the incoherent background is reduced by means of dynamic nuclear polarisation of the proton spins. In the longer term, this technique could be employed to improve substantially the signal-to-noise ratio in neutron diffraction experiments on biological crystals.

44

Thursday, 05 July 2012

Session: Instrumentation and methods - polarised neutrons

Chair : A. Menelle

Towards TOF spectroscopy and Laue diffraction with spherical polarimetry

Werner Schweika1,2and Yixi Su3

1Jülich Centre of Neutron Science (JCNS), Forschungszentrum Jülich GmbH, Jülich Germany 2European Spallation Source, ESS AB Lund, Sweden, werner.schweika@esss.se

Current instrumentation such as the DNS at FRM II or the D7 at ILL allows for an efficient mapping of reciprocal space of single crystal samples including XYZ polarization analysis as will be illustrated by recent examples of complex magnetic systems, e.g. layered kagome structures studied at the DNS instrument. With a recent development including the polarization reversal, a complete separation and analysis of scattering terms from single crystals can be achieved. An extension of the separation method for 2D detectors that are now being installed at DNS will be discussed. A further development has been a precession technique, which allows for the determination of the off-diagonal terms of the polarization scattering tensor, typically used in zero-field polarimetry to reveal chiral and nuclear magnetic interference and correlations. This precession technique for spherical polarimetry is particularly efficient for TOF and multi-detector instruments, since all S(Q,E) can be accessed simultaneously. It will be shown that the precession technique for polarimetry can be extended further for using a wide wavelength band, which results in an interesting new instrument concept for a neutron TOF Laue instrument at the ESS dedicated for magnetism studies. [1] W. Schweika, Journal of Physics: Conference Series 211 (2010) 012026. XYZ polarization analysis of diffuse scattering from single crystals [2] W. Schweika, S. Easton and K.U. Neumann, Neutron News 16 (2005) 14. Vector polarization analysis on DNS.

45

Polarized 3He production exceeding 100 liters per day using Spin Exchange Optical Pumping

David Watt, Iulian C. Ruset, Jan Distelbrink, Jeff Ketel, Steve Ketel, F. William Hersman,

Xemed LLC, 16 Strafford Avenue, Durham, NH 03824 USA Department of Physics, University of New Hampshire, Durham, NH 03824 USA

Spin Exchange Optical Pumping (SEOP) utilizes diode lasers to illuminate a heated mixture of alkali vapor, 3He gas, and 100 torr nitrogen in enclosed glass cells. The inverse relationship between the cell size and the gas pressure imposes limits on the amount of 3He that can be polarized at one time, typically under 2-3 STP liters. We have developed a 3He polarizer that operates inside a pressure vessel that continuously nulls differential pressure across the glass cell. Our glass cells are 10cm in diameter, 110cm long (~8.5 liter) with thin walls (approximately 3mm) fabricated from either aluminosilicate or borosilicate glass. We charge the cell with a triple-distilled potassium-rubidium alkali mixture. Once assembled, we fill the cell with up to six amagat of helium, using a 50:1 mixture of 4He/3He to limit costs. In tests performed in 2009 we illuminated the cell with a 1.2 kW broadband diode laser centered at 795nm with a 3nm spectral line width. We achieved spin-up rates of 20% per hour on 50 STP liters, sufficient to produce 100 liters per day. Due to the modest relaxation lifetime T1 of 10 hour of 3He in this cell, asymptotic polarization was limited to ~50%. We are currently assembling a next-generation version of this high-volume 3He polarizer, focusing on improving the glassware and laser. The 2.5kW laser (described elsewhere at this meeting) is wavelength locked to 795 nm capable of achieving a spectral line width of 0.3nm. Several improvements in glassware fabrication are expected to yield T1 exceeding 50 hours. We seek production exceeding 100 liters per day at >75% polarization in a portable, automated, and reliable SEOP system.

Demonstration of spatial intensity modulated TOF SESANS with simple tools

Jeroen Plomp, Wouter de Landgraaf

Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands

A new concept was presented by R. Gähler [1] to use polarised neutron to create a modulated beam to increase resolution on conventional instruments. This is the principle that is used in the new approach for SESANS [2]. With this it will be possible to measure a SESANS signal downstream of the analyser, so a magnetic sample or magnetic field at the sample position will not have any influence on the final SESANS signal. Another and maybe a more important advantage is that the conventional SANS signal is measureable at the same time. There is no physical limitation in for higher q-values (20 nm and smaller length scales) by flippers and analyser like in the conventional SESANS method. It will be possible to have a SANS instrument that includes a “beamstop detector” that measures low q-values (length scales from 20 nm to 20 micron) and high q-values (from 1 to 200 nm) by means of the conventional SANS detector at the same time. We have performed a series of TOF experiments that clearly demonstrate the principles and advantages of this method. This includes sample measurements downstream of the analyser. Normally one uses a high resolution position sensitive detector for this method but we show that a grating in combination with a conventional He3 tube detector and TOF can be a nice alternative. [1] R. Gähler, A certain class of beam modulation techniques and its potential applications, PNCMI Polarized Neutron School, 2006. [2] W.G.Bouwman et. all, Spatial modulation of a neutron beam by Larmor precession, Physica B, Condensed Matter, Volume 404, Issue 17, 1 September 2009, Pages 2585-2589

46

Frontiers of Neutron Larmor Diffraction

T. Kellera,b

, A. Waltersa

, B. Keimera

aMax-Planck-InstitutfürFestkörperphysik, Stuttgart, Germany bForschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Garching, Germany

The TRISP spectrometer at the FRM II is based on the resonance spin-echo technique (NRSE) invented by Golub and Gähler and applies the spin echo phonon focusing proposed by Mezei. Linewidths of dispersive excitations with energies up to 50meV can be measured with a resolution in the µeV-range. The instrument also incorporates Rekveldt’s Larmor diffraction (LD) technique, on which we will focus here. In the present configuration, the lattice spacing can be measured with a relative resolution of 10-6, i.e. more than one order of magnitude more sensitive than conventional diffraction techniques. The technique also allows to measure the distribution of d values (second order stress). Applications of the LD technique include the measurement of thermal expansion under extreme conditions, the determination of mechanical stress, observation of small Bragg peak splitting, and the measurement of magnetic domain sizes.. Limitations of the LD technique as well as the outline of a dedicated Larmor-diffractometer will be discussed. In the present contribution we will give a short introduction, review recent high lights and outline the design of a dedicated Larmor diffratometer pushing the relative resolution to 10-7, a limit which is imposed by the intrinsic Darwin width in perfect crystals.

A beam divergence correction for NRSE spectrometer using polygonal 2D-focusing supermirrors

Tatsuro Oda

1, Masahiro Hino

2, Masaaki Kitaguchi

2 and Yuji Kawabata

2

1) Department of Nuclear Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan t_oda@nucleng.kyoto-u.ac.jp

2) Research Reactor Institute, Kyoto University (KURRI), Kumatori, Osaka 590-0494, Japan

In a neutron resonance spin echo (NRSE) spectrometer, a couple of resonance spin flippers (RSF) and zero magnetic fields make a relative phase of two spin eigenstates. The deviation of the flight length of the divergent neutron beam makes the phase difference not due to the inelastic scattering in a sample and decreases the contrast of the spin echo signals. In the conventional NSE, Fresnel coils are used to cancel the additional phase difference, however, it is very difficult to apply them to NRSE because the spin quantization axis need to be changed adiabatically from the vertical direction of RSFs into the longitudinal direction of Fresnel coil with no disturbance of the phase difference. By inserting 2-dimensional (2D) elliptic focusing mirrors between each pair of RSFs, the flight path lengths between the couple of RSFs are independent of the beam divergence [1]. It is, however, not easy to realize such 2D elliptic focusing mirror with large scale. We numerically investigate the relation of energy resolution of NRSE and the beam divergence correction by polygonal 2D-elliptic focusing mirrors. Kyoto University and KEK are constructing a new beam line for VIN ROSE (MIEZE and NRSE spectrometers) at BL06 in J-PARC/MLF. We discuss the feasibility of the polygonal focusing mirror as a beam divergence correction device for NRSE of VIN ROSE. References [1] M. Kitaguchi, M. Hino, Y. Kawabata, S. Tasaki, R. Maruyama, T. Ebisawa, Physica B 406 (2011) 2470

47

Larmor labeling methods: Neutron Resonance Spin Echo spectroscopy beyond standard line width measurements

Felix Groitl

1, Katharina Rolfs

1, Diana Quintero-Castro

1, Klaus Kiefer

1,

Thomas Keller2, 3

, Klaus Habicht1

1Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, 14109 Berlin, Germany, felix.groitl@helmholtz-berlin.de

2Max-Planck-Institute for Solid State Research, Heisenbergstraße 3, 70569 Stuttgart, Germany 3FRM II, Lichtenbergstraße 1, 85748 Garching, Germany

We explore new territory for Neutron Resonance Spin Echo (NRSE) spectroscopy beyond measuring lifetimes of elementary excitations and present two experiments which benefit from the high resolution offered by this method. The first experiment aims at separating modes split in energy which are difficult to resolve with standard neutron scattering techniques [1]. In this context it is essential to take violation of the spin echo conditions and arbitrary local gradients of the dispersion surface into account which we provide with an extended model of the NRSE resolution function [2]. The second class of experiments deals with line shape analysis relevant for the phenomenon of asymmetric line broadening [3]. Measurements were performed on Cu(NO3)2⋅2,5D2O, a model material for a 1-D bond alternating Heisenberg chain, and on Sr3Cr2O8, a dimerized spin-1/2 antiferromagnet. This is the first time this effect has been measured with high-resolution NRSE. The particular advantage of the NRSE method is the direct access to the line shape since there is no convolution of the signal with the resolution function of the spectrometer. Our experimental results show clear evidence for double peaked line shapes rather than a continuous asymmetry. References [1] F. Groitl et al., Physica B 406 12 2342-2345 (2011) [2] K. Habicht et al., Physica B 350 E803-806 (2004) [3] D. A. Tennant et al., Physica Review B 85 1 014402 (2012)

Latest developments of polarized neutron scattering instrumentation at the JCNS

Alexander Ioffe

Juelich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Outstation at FRM II, Lichtenbergstr. 1, 85747 Garching, Germany *E-mail: a.ioffe@fz-juelich.de

During last years significant efforts in developments and upgrade of polarized neutron scattering

instrumentation have been undertaking at the Jülich Centre for Neutron Science (JCNS), thus allowing to keep it in line with continuously changing scientific request.

New correction elements for the NSE spectrometers allows for pushing their resolution towards 1 µsec; the use of position-sensitive detectors at the diffuse scattering spectrometer DNS increasing the efficiency by an order of magnitude.

Successful in-house developments of 3He neutron spin filters employing the on-beam gas polarization provide the basis for the polarization analysis in a wide Q-range as at the neutron reflectometer MARIA (up to 3 Å-1, swiveling/rotating detector arm) and small-angle scattering diffractometers KWS (up to 0.6Å-1). Developments of the PASTIS-like wide-angle 3He analyzers are carried out for the polarization analysis in a large scattering angle. They will allow for simultaneous XYZ and 3-d polarization analysis in the angle up to 140° at time-of-flight spectrometers like DNS and TOPAS

48

MARIA – The high-intensity polarized neutron reflectometer of JCNS

S.Mattauch1

, U.Rücker2, D. Korolkov

1, E.Babcock

1, A.Ioffe

1 and Th.Brückel

2

1Jülich Centre for Neutron Science (JCNS), Garching, Germany 2JCNS, Forschungszentrum Jülich, Jülich, Germany

s.mattauch@fz-juelich.de

The JCNS has installed the new, high-intensity reflectometer MARIA in the neutron guide hall of the FRM II reactor in Garching. This instrument uses a velocity selector for the monochromatization of the neutron beam, an elliptically focussing guide to increase the flux at the sample position and a double-reflecting super mirror polarizer to polarize the entire cross-section of the beam delivered by the neutron guide. Unique features of MARIA include (i) vertical focussing with an elliptic guide from 170 mm down to 10 mm at the sample position, (ii) reflectometer and GISANS mode, (iii) polarization analysis over a large 2d position sensitive detector as standard, (iv) adjustable wavelength spread from 10 to 1 % by a combination of velocity selector and chopper, (v) flexible sample table using a Hexapod for magnetic field and low temperature sample environment and (vi) in-situ sample preparation facilities. Together with a 400 x 400 mm² position sensitive detector and a time-stable ³He polarization analyser based on Spin-Exchange Optical Pumping (SEOP), the instrument is dedicated to investigate specular reflectivity and off-specular scattering from magnetic layered structures down to the monolayer regime. In addition the GISANS option can be used to investigate lateral correlations in the nm range. This option is integrated into the reflectometer’s collimation, so it can be chosen during the measurement without any realignment. MARIA is a state of the art reflectometer at a constant flux reactor. It gives you the opportunity to investigate easily reflectivity curves in a dynamic range of up to 7-8 orders of magnitude, off-specular scattering, GISANS and even simple SANS measurement. We will discuss how MARIA can help you to investigate the depth resolved vector information of your magnetic samples.

Studying slow dynamics and depolarizing systems with NRSE-MIEZE at the ESS

W. Häußler1,2, G. Brandl1,2, R. Georgii1,2, P. Böni2

1Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universität München, Lichtenbergstr.1, 85747 Garching, Germany, Wolfgang.Haeussler@frm2.tum.de

2Physik Department E21, Technische Universität München, James-Franckstr., 85748 Garching, Germany We present a design study for a NRSE-MIEZE-type Larmor precession spectrometer focused on the investigation of slow dynamics in magnetic materials, strongly incoherently scattering samples and samples under extreme conditions. The NRSE-MIEZE technique combined with a multi-detector array based on state of the art technology provides a wide (q,t)-range. This presentation focuses on the design for a versatile instrument that implements both flavours of MIEZE techniques, MIEZE-I and -II, allowing for depolarizing sample environment and large detector solid angle, respectively. Variable focusing neutron guides will be used to optimize measurements of small samples under extreme conditions. The design goals are to utilize a wide wavelength band of 3–15 Å, in order to achieve time resolutions in the ps to μs range. The q-range will cover 10-3-2 Å-1 with resolution up to 10-4 Å-1 at small scattering angles.

49

A Polarized 3He Neutron Spin Analyzer for SANS Polarization Analysis W.C. Chen

1,2, K.L. Krycka

1, S.M. Watson

1, Q. Ye

1, T.R. Gentile

1, and J.A. Borchers

1

1National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and 2University of Maryland, College Park, Maryland 20742, USA, wcchen@nist.gov

Supermirrors have typically been used for polarizing well-collimated neutron beams with high polarization and transmission, but their limited angular acceptance makes them impractical for polarization analysis on small-angle neutron scattering (SANS) instruments. We have implemented SANS polarization analysis with 3He neutron spin filters (NSFs) at the NIST Center for Neutron Research for studies of, for example, magnetic nanoparticle assembly [1], multiferroics [2], and giant magnetostriction [3]. Key issues for practical application for NSFs to SANS polarization analysis are sufficient angular coverage, long polarization storage times in the presence of stray fields from strong sample magnetic fields, and the capability to invert the 3He polarization and thus the neutron polarization. We present our recent development in SANS polarization analysis and a survey of scientific applications. Our spin filter analyzers are polarized off-line by spin-exchange optical pumping. Improvements in optical pumping have yielded initial 3He polarization values of 75% - 85%. We will present magnetic field apparatus that allows us to have relaxation time up of 200 hours when a transverse 1.5 T field is applied to the sample. SANS polarization analysis requires accurate knowledge of polarization and spin flip efficiencies. We report determination of these polarization efficiencies, which can be conveniently obtained with a 3He analyzer. Finally we discuss the plan for performing in-situ spin-exchange optical pumping on the SANS instrument. [1] K. Krycka et al., Phys. Rev. Lett. 104, 207203 (2010). [2] M. Ramazanoglu et al., Phys. Rev. Lett. 107, 207206 (2011). [3] M. Laver et al., Phys. Rev. Lett. 105, 027202 (2010).

Neutron spin filtering with dynamically polarized protons using photo-excited triplet states

P. Hautle1,*

, T.R. Eichhorn1,2

, M. Haag1, B. van den Brandt

1, W.Th. Wenckebach

1,&

1 Paul Scherrer Institute, CH-5232 Villigen, Switzerland; & academic guest at PSI 2 LIFMET, EPFL, CH-1015 Lausanne, Switzerland * corresponding author: patrick.hautle@psi.ch

Dynamic nuclear polarization (DNP) has lead to the development of polarized targets with which the role of spin in nuclear and particle interactions is investigated. It also opened new possibilities in neutron science by exploiting the strong spin dependence of the neutron scattering on protons. A neutron spin filter has been built, which is based on a novel DNP method that uses the photo-excited triplet state of pentacene guest molecules to polarize the protons in the host single crystals of naphthalene. Compared to the classical DNP scheme, in triplet DNP the requirements for the cryogenic equipment and the magnetic field are significantly relaxed making technically simpler systems with open geometries possible. The spin filter is operated in 0.3 T and about 100 K and has performed reliably over periods of several weeks [1]. The analyzing power obtained – A = 0.17 – was still modest and limited by the low repetition rate of the laser system. The neutron beam was also used to measure the proton spin polarization as a function of position in the naphthalene sample. The polarization was found to be homogeneous, even at low laser power. This is in contradiction to existing models describing the photo-excitation process and crucial for the further development of the method for future experiments with polarized neutrons. [1] M. Haag, B. van den Brandt, T.R. Eichhorn, P. Hautle, W.Th. Wenckebach, Nuclear Instruments and Methods in Physics Research Section A (2012) (in press) doi: 10.1016/j.nima.2012.03.014.

50

Wide Angle Polarization Analysis with Polarized 3He Neutron Spin Filters

T. Gentile, Q. Ye, W. Chen, R. Erwin, C. Fu, S. Watson, C. Broholm, J. Rodriguez-Rivera, V. Thampy

Stop 8461, NIST, 100 Bureau Drive, Gaithersburg, Maryland USA, thomas.gentile@nist.gov

We report substantial improvements in a compact wide angle neutron spin filter system that was recently employed on the Multi-Axis Crystal Spectrometer (MACS) at the U.S. National Institute of Standards and Technology Center for Neutron Research (NCNR). In the MACS instrument, simultaneous neutron detection from twenty independent channels covering an angular range of 240 degrees around the sample region provides more than an order of magnitude gain in detection efficiency as compared to a conventional triple axis spectrometer. For polarized neutron scattering experiments on MACS, a cylindrical 3He cell in a shielded RF solenoid polarizes the neutrons incident on the sample. After scattering from the sample, neutrons are detected after passing through a 3He analyzer cell. Both cells and the sample are contained within a uniform magnetic field provided by a vertical solenoid. Nuclear magnetic resonance is employed to reverse the incident neutron polarization and monitor the 3He polarization in all cells. In the first experiment using this apparatus, Friedel-like oscillations from interstitial iron in superconducting FeSeTe were studied. Due to issues with temperature-dependent relaxation in quartz wide-angle cells, this experiment was carried out with cylindrical GE180 cells, limiting the angular coverage. We will present results for new, GE180 analyzer cells that cover 120 degrees, and have long lifetimes (100 - 200 h) and high polarizations (>70%). Hybrid spin exchange optical pumping (SEOP) and high power diode lasers narrowed by chirped volume Bragg gratings are employed to polarize the 3He cells. During the shutdown of the NCNR, the 3He polarization has been measured by electron paramagnetic resonance (EPR) and will be confirmed by neutron transmission. Two of these wide-angle cells covering a total angle of 240 degrees will be used as the neutron spin analyzers in upcoming MACS experiments. Additional progress includes an improved holding field solenoid and decreased spin-flip losses.

Polarizing Fe-Co-Fe planar waveguide for neutron microbeam production

S.V. Kozhevnikova,b,c

*, F. Ottb,d

, A. Rühmc, and J. Major

c

aFrank Laboratory of Neutron Physics, JINR, 141980 Dubna Moscow Region, Russian Federation; bCEA, IRAMIS, Laboratoire Léon Brillouin, F-91191 Gif sur Yvette, France;

cMax-Planck-Institut für Intelligente Systeme (formerly Max-Planck-Institut für Metallforschung), D-70569 Stuttgart, Germany; kozhevn@nf.jinr.ru

dCNRS, IRAMIS, Laboratoire Léon Brillouin, F-91191 Gif sur Yvette, France Planar neutron waveguides transform a conventional highly collimated neutron macrobeam into an extremely narrow (about 100 nm), though slightly divergent (0.1°), microbeam [1]. Polarized neutron microbeams [2,3] can be used for the investigation of magnetic nanostructures with high spatial resolution. One difficulty concerning the usefulness of such a polarized microbeam is its divergence which is large and excludes the usage of a spin-flipper between the waveguide and the sample. Consequently, the use of a switchable polarizer waveguide, i.e. a ferromagnetic waveguide switchable with an external magnetic field can be very advantageous. We found that the polarizing efficiency of magnetic Fe-Co-Fe waveguides can be high enough for practical purposes. The polarized neutron microbeam produced by this structure has been characterized experimentally using the polarized neutron reflectometer NREX at FRM2. References [1] F. Pfeiffer, V. Leiner, P. Høghøj, I. Anderson, Phys. Rev. Lett. 88 (2002) 055507. [2] S.V. Kozhevnikov, A. Rühm, F. Ott, N. K. Pleshanov, J. Major, Physica B 406 (2011) 2463. [3] S.V. Kozhevnikov, A. Rühm, J. Major, Crystallography Reports 56 (2011) 1207.

51

Poster Session Programme

Poster Session A, Monday, July 2nd 2012

A01

Quantum criticality in Mn1-xFexSi studied by SAPNS

E. Moskvin1, N. Potapova1, V. Dyadkin1, C. Dewhurst2, S. Siegfried3, D. Menzel3, S. Grigoriev1 1Petersburg Nuclear Physics Institute, Gatchina, St.-Petersburg, 18830, Russia, mosqueen@pnpi.spb.ru

2Institut Laue-Langevin BP 156, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 France 3Institut fuer Physik der Kondensierten Materie, TU Braunschweig, Braunschweig, Germany

We studied the critical spin fluctuations and spin structure in Mn1−xFexSi, compounds in the vicinity of the quantum phase transition at x ≈ 0.15. Compounds with x = 0.1, 0.15, 0.16, 0.20 were studied by ac susceptibility and polarized neutron small-angle scattering. In accord with our previous study [1] the compound with x = 0.10 undergoes the transition from the paramagnetic to helimagnetic phase at Tc ≈ 7 K through the well distinguishable crossovers: (i) from paramagnetic to partially chiral and (ii) from partially chiral to fully chiral fluctuating state. The compounds with x = 0.15 and 0.16 show enhancement of the criticality with lowering temperature to T = 1.7 K. We obtained temperature and magnetic field dependencies of the inverse correlation length, , susceptibility, and magnetic structure wave vector, k0, for the above-mentioned compounds. No spin ordering was observed for these compounds. Extrapolation to T = 0 verifies our assumption of their closeness to the quantum phase transition. Compound with x = 0.20 does not exhibit any long-range order or fluctuations down to the lowest measured T. It clearly means that this concentration is already above the critical value xc of quantum phase transition. References [1] Sergey V. Grigoriev, Evgeny V. Moskvin, Vadim A. Dyadkin, Daniel Lamago, Thomas Wolf, Helmut Eckerlebe, and Sergey V. Maleyev, Physical Review 83 (2011) 224411. Chiral criticality in the doped helimagnets Mn1−yFeySi.

52

A02

Neutron Resonant Spin-Echo techniques using ZETA option on thermal TAS IN22 – Beyond inelastic spectroscopy

N. Martin

1,2, L.-P. Regnault

2, S. Klimko

3, K. Zhernenkov

4, D. Gorkov

4, B.P. Toperverg

4

1CEA-Grenoble, INAC-SPSMS-MDN, 38054 Grenoble Cedex 9, France 2FRM II, Technische Universität München, 85747 Garching, Germany

3Laboratoire Léon Brillouin, CEA-CNRS, CEA-Saclay, 91191 Gif-sur-Yvette, France 4Ruhr-Universität Bochum, 44780 Bochum, Germany

ZETA is an up-to-date Neutron Resonant Spin-Echo (NRSE) option which is commonly installed on thermal three-axis spectrometer (TAS) IN22, located at Institut Laue Langevin and operated as a CEA/FZJ CRG instrument. Its high flexibility allows performing, beyond inelastic spectroscopy with some µeV resolution, high accuracy Larmor diffraction (NLD, see e.g. [1] and references therein) as well as time-resolved measurements by making use of the MIEZE principle ([2]). Here, we present selected examples to show the capabilities of the ZETA/IN22 for accomplishing such experiments. We especially focus on

(i) The survey of magneto-elastic effect in BaM2(XO4)2 (M = Co, Ni; X = As, P) layered quasi two-dimensional magnets,

(ii) The direct observation of magnetization dynamics in a thin Fe-film subjected to crossed DC and AC magnetic field with frequencies 40 < fAC < 200 kHz.

Experimental issues and future prospects are also discussed. References [1] N. Martin, L.-P. Regnault, S. Klimko, J.E. Lorenzo and R. Gähler, Physica B 406 (2011) 2333 [2] R. Gähler, R. Golub and T. Keller, Physica B 180-181 (1992) 899.

A03

The Magnetic Defect in Antiferromagnetic Gamma Manganese Copper

T. J Hicks

a , A. Mulders

a*, C. Pappas

b†

aSchool of Physics, Monash University 3800, Australia trevor.hicks@monash.edu.au bHelmholtz-Zentrum Berlin für Materialien und Energie GmbH, Glienicker Str. 100, D-14109 Berlin

Single crystals of face centred tetragonal manganese-copper alloy containing 10 at. % copper were examined with polarised neutron scattering on SPAN at HMI. Of interest was the large diffuse scattering intensity near the 001 position. This is due to the magnetic defect induced by the copper impurity in the antiferromagnetic manganese and the components transverse to the antiferromagnetic direction of this defect are those seen at the 001 position. Uniaxial polarisation analysis along the three Cartesian directions was used to attempt to isolate the magnetic scattering. The polarisation dependence was modelled using chiral components to make up the defect. These in one limit result in a collinear picture and in the other limit are helical. The results of the analysis will be discussed in terms of the likely chirality of the defect. *Now at: School of PEMS, Univ. of New South Wales, ADFA, Canberra, ACT 2600, Australia †Now at: Delft University of Technology, Delft, Netherlands

53

A04

Evolution of spin structure in MnSi close to TC under magnetic field

S.V. Grigoriev,

1 N.M. Potapova,

1 E.V. Moskvin,

1 V.A. Dyadkin,

1 Ch. Dewhurst,

2 S.V. Maleyev

1

1 Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia

1 Institute Laue-Langevin, F-38042 Grenoble Cedex 9, France

The temperature evolution of the spin structures of MnSi in the magnetic field close to Tc is studied by polarized neutron small angle scattering. Three magnetic states are observed: (i) the critical spin helix fluctuations with randomly oriented kF (ii) the conical phase with kC || H and (iii) the hexagonal A-phase structure with kA ⊥ H. It is known that in zero field MnSi undergoes a complex transition from the para- to heli-magnetic phase through continuous, yet well distinguishable crossovers: (i) from paramagnetic to partially chiral state at T* ≈ 31.5 K, (ii) then to highly chiral fluctuating state at Tk ≈ 30 K and (iii) then to helical structure at Tc ≈ 29 K [1]. Upon field cooling at H = 0.17 T the conical phase appears at T = T* and it coexists with the critical fluctuations (kC ≠ kF). The scattering function of the helix fluctuations is well described by the Lorentzian with the width ê at T* being equal to 2kC. The hexagonal A-phase structure is added to the existing ones upon further cooling at T = Tk (kA ≈ kC). The diffraction peaks for both structures are well described by Gaussian with the width, limited by the setup resolution function. The A-phase develops upon further cooling below Tc, while though coexisting conical phase remains suppressed. Below T = 28 K both the A-phase and critical fluctuations disappear and the conical phase is observed only. We discuss our findings in terms of the energy competition between three phases at different temperatures. References [1] S.V. Grigoriev, E.V. Moskvin, V.A. Dyadkin, et.al, Phys.Rev.B, 83 (2011) 224411.

A05

Numerical calculation of magnetic form factors of complex shaped nano-particles coupled with micro-magnetic simulations.

Fatih Zighem, Frédéric Ott

Université Paris XIII, LSPM CNRS-Université Paris XIII 99 avenue Jean-Baptiste Clément 93430 Villetaneuse, France CEA/CNRS, IRAMIS, Laboratoire Léon Brillouin, 91191 Gif sur Yvette, France

During the recent years, chemists have made progress in the synthesis of magnetic objects with complex geometrical shapes [1]. The prediction of the internal magnetic structures of these objects is non-trivial. We have developed numerical procedures in order to calculate the magnetic form factors of nano-objects with complex geometrical shapes and non-homogeneous magnetization distributions. In particular, we describe a numerical procedure which allows calculating 3D magnetic form factors of nano-objects from realistic magnetization distributions obtained by micromagnetic calculations using the Nmag freeware package [2]. The use of these routines will be illustrated in the case of the canonical cases of spheres, rods and platelets. We shall also discuss the case of some realistic objects. This work is a first step towards a 3D vectorial reconstruction of the magnetization in nanoparticles using neutron scattering techniques. [1] Kinetically Controlled Synthesis of Hexagonally Close-Packed Cobalt Nanorods with High Magnetic Coercivity. Y. Soumare, C. Garcia, T. Maurer, G. Chaboussant, F. Ott, F. Fiévet, J.-Y. Piquemal and Guillaume Viau, Adv. Funct. Mater. 2009, 19, 1–7. DOI: 10.1002/adfm.200800822. [2] http://nmag.soton.ac.uk/nmag/

54

A06

The new calibration technique for SESANS-device.

E.V.Velichko1, Yu.O.Chetverikov

1, L.A.Akselrod

1, V.N.Zabenkin

1, V.V.Piyadov

1,

A.A.Sumbatyan1, W.H.Kraan

2, S.V.Grigoriev

1

1Petersburg Nuclear Physics Institute, 188300 Gatchina, St Petersburg, Russia, evgen@pnpi.spb.ru 2Dept. R3, Faculty of Applied Sciences, Delft University of Technology, 2629 JB Delft, The

Netherlands. Spin-echo small-angle neutron scattering (SESANS) is a novel method to determine the structure of materials in real space [1]. The method is based on the Larmor precession of polarized neutrons transmitted through two successive precession devices before and after the sample, which encodes the scattering angle into a net precession angle. Construction of the SESANS-device in Gatchina at the VVR-M reactor had started at 2005. We present the first results obtained at the device. Samples of the opal-like colloidal crystals consisted of the spherical particles SiO2 with sizes 320, 408 and 516 nm, respectively, were investigated. Since one cannot directly measure the spin-echo length, we have to calibrate the scale of measured values, e.g. to relate uniquely the magnetic field at the centre of the magnet and the spin-echo length. The calibration curve was performed using the sample with spheres size of 516 nm. Then, assuming the setup calibrated we have studied the other two samples. The values for the size of the sphere obtained from the SESANS measurements coincide within the error bars with the nominal values of the samples. Our results have shown that this method of calibration is legitimate for SESANS-devices. References [1] Rekveldt, M. Th. Nucl. Instrum. Methods B, 114 (1996) 366–370.

A07

Shape-induced superstructure in concentrated ferrofluids

S. Disch

1,2, E. Wetterskog

3, R. P. Hermann

1, A. Wiedenmann

2, G. Salazar-Alvarez

3,

L. Bergström3, Th. Brückel

1

1JCNS and PGI, JARA-FIT, Forschungszentrum Jülich, Germany 2Institut Laue-Langevin (ILL), Grenoble, France

3Dept. of Materials and Env. Chemistry, Arrhenius Laboratory, Stockholm University, Sweden Magnetic nanoparticles, as compared to the bulk material, exhibit unique physical properties such as an enhanced magnetic anisotropy, important for applications in data storage because it impedes magnetization reversal. The magnetic anisotropy is strongly related to the surface and shape of the nanoparticles. The influence of nanoparticle shape on the degree of surface spin canting in iron oxide nanoparticles has recently been reported [1]. In this contribution we will present the field-induced ordering of concentrated ferrofluids. In particular, the influence of shape anisotropy on interparticle interactions will be highlighted in our polarized SANS study on highly concentrated iron oxide nanoparticle dispersions. Whereas a spatially disordered, short range ordered hard spheres interaction potential is found for spherical nanoparticles, nanocubes of a comparable particle size reveal a more pronounced interparticle interaction and the formation of linear aggregates. Contributions of van-der-Waals and dipolar interparticle interactions to the field-induced ordering will be discussed. [1] S. Disch et al., New J. Phys. 14 (2012) 013025. Quantitative spatial magnetization distribution in iron oxide nanocubes and nanospheres by polarized small-angle neutron scattering

55

A08

Magnetic anisotropy in the interface of Fe3O4/Mn3O4 superlattices probed by neutron reflectivity

Chin Shan Lue1, L. J. Chang

1,2, M. Takeda

3, C. H. Lee

2, G. Chern

4

1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan, cslue@mail.ncku.edu.tw

2Department of Engineering and System Science, National Tsing Hua University, HsinChu 30013, Taiwan 3 Quantum Beam Science Directorate, JAEA, Tokai, Ibaraki 319-1195, Japan

4 Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan

Fe3O4 and Mn3O4 both have spinel structure and some physical similarities. However, Fe3O4 is well known to show the Verwey transition, while Mn3O4 shows ferrimagnetism and substantially high magnetic anisotropy. The magnetic anisotropy Fe3O4/Mn3O4 superlattices is thus expected to possess highly magnetic anisotropy, and to have an effect on the antiparallel state (spin–flop phase) and compensation point. High quality Fe3O4/Mn3O4 superlattices grown on MgO [110] have been prepared by molecule-beam epitaxy, and characterized by in-situ reflection high-energy electron diffraction and ex-situ x-ray diffraction. We will report polarized neutron reflectivity results on Fe3O4/Mn3O4 superlattices for the temperature range cross both Fe3O4 and Mn3O4 transitions to investigate the anisotropy and magnetic configuration around the compensation point of the system.

A09

Effect of Sn surfactant in Fe/Si multilayers probed by neutron reflectivity S. M. Amir

1, M. Gupta

1, A. Gupta

1, M. Horisberger

2 and J. Stahn

3

1UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 001, India 2Laboratory for Developments and Methods, PSI, 5232 Villigen PSI, Switzerland3Laboratory for Neutron Scattering,

PSI, 5232 Villigen PSI, Switzerlan

Fe/Si multilayers are important because of its applications in magnetic and neutron optical devices [1,2]. Spontaneous interdiffusion occurs at Fe/Si and Si/Fe interface as a result Fe-silicide layer is formed across the interfaces. Properties of the Fe/Si multilayer depend on the type of Fe-silicide spacer layer [3]. It has been found that Fe-on-Si and Si-on-Fe interface is asymmetric which is due to the difference in the surface free energies of Fe (γFe = 2.5 Jm-2) and Si (1.1 Jm-2) [4]. This difference in the surface free energies can be minimized using a third element the so called surfactant [5,6]. In this work Sn (γFe = 0.65 Jm-2) surfactant has been used to prepare with and without Sn surfactant Fe/Si multilayer using magnetron sputtering technique. Polarized and un-polarized neutron reflectivity was done to characterize the interface roughness and interdiffusion. It was found that Bragg peak reflectivity is enhanced in case of the sample when Sn surfactant is present in the multilayer. Enhancement of the Bragg peak indicates the sharpening of the interface with the addition of Sn surfactant. Fitting of the polarized neutron reflectivity reveals that Fe-silicide layer is non magnetic for both the samples prepared with and without Sn surfactant however thickness of the Fe-silicide layer is small for the sample prepared with Sn surfactant. Further X-ray diffraction measurements were done on these samples and it was found that magnetron sputtered Si layer is amorphous for both the samples. [3] J. J. Vries et.al. ; Phys. Rev. Lett. 78 (1997) 3023 [4] P. Hoghoj et. al. ; Physica B 267 (1999), 355 J. Stahn and D. Clemens Appl. Phys. A 74 (2002) s1532 [5] E. E. Fullerton et. al. ; J. Magn. Magn. Mater. 117 (1992) L301 [6] A. Gupta, D. Kumar and V. Phatak; Phys. Rev. B 81 (2010) 155402 [7] M. Copel et. al. ; Phys. Rev. Lett. 63 (1989) 632 [8] M. Gupta et. al. ; Appl. Phys. Lett. 98 (2011) 101912

56

A10

Study of induced chirality in Ho/Y myltilayers

V. Tarnavich1, D. Lott

2, S. Mattauch

3, S.Grigoriev

1

1Petersburg Nuclear Physics Institute, 188300 Gatchina, Russia, tarnavich@lns.pnpi.spb.ru 2Helmholtz Zentrum Geesthacht, 21502 Geesthacht, Germany

3Jülich Centre for Neutron Science (JCNS), 85747 Garching, Germany

A few years ago we have demonstrated that Dy/Y magnetic multilayer structures (MMLs) possess a coherent spin helix with a preferable chirality induced by the magnetic field [1]. A magnetic field applied in the plane of the sample upon cooling below TN is able to repopulate the otherwise equal population numbers for the left- and right-handed helixes. The experimental results strongly indicate that the chirality is caused by Dzyaloshinskii-Moriya interaction due to the lack of the symmetry inversion on the interfaces. We supposed that the same effect of an applied magnetic field on the chirality of the helix spin structure can be observed in similar MMLs with different Rare-Earth elements, such as Ho. Two samples [Ho4.2 nm/Y3.0nm]20 and [Ho3.0

nm/Y3.0 nm]20 grown along the c axis [001] of the Ho and Y hcp structure by molecular-beam-epitaxy techniques were chosen for the investigations. The polarized neutron experiments were carried out at the MARIA reflectometer at FRM 2 (JCNS). The chirality parameter γ=(I+- I-)/(I+ + I-) was measured and directly related to the imbalance between the left- and right-handed spiral, where I+/- is the integrated intensity of the helical peak with up (+) and down (-) neutrons. For the sample Ho4.2 nm/Y3.0nm we found non-zero chirality (of order of 0.15), which depends on the temperature below TN = 110 K and smaller the field of 1 T. For Ho3.0 nm/Y3.0 nm the field induced chirality was almost zero within the whole (H-T) ranges. We assume that the field induces the chirality due to coupling to the uncompensated moments of the helix in a Ho layer [1] and difference between two MMLs is caused by the difference in the thickness of the Ho layers. [1] S. V. Grigoriev et al., Phys.Rev. B 82, 195432 (2010)

A11

Influence of Si interlayer on diffuse scattering profile of Fe/Ge polarizing supermirror

R. Maruyama, D. Yamazaki, H. Hayashida, and K. Soyama

J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan E-mail: ryuji.maruyama@j-parc.jp

The neutron polarizing supermirror is one of the most important optical devices for polarizing neutron beams. Polarizing supermirrors need to display high polarization efficiencies at low external magnetic fields to meet a variety of research demands. As shown by Hino et al., the Fe/Si/Ge/Si multilayer, obtained by adding thin interlayers of Si into an Fe/Ge multilayer, is effective in reducing the external field strength necessary to achieve efficient neutron polarization [1]. We have demonstrated that a reduction in compressive stress in the Fe/Si/Ge/Si multilayer permits the use of lower external filed strength to achieve efficient neutron polarization [2]. In this study, the influence of the Si interlayer on diffuse scattering profile of Fe/Ge neutron polarizing supermirror is investigated since the diffuse scattering intensity from a polarizing supermirror should be minimized for various applications. The discussion on the methods and result of the measurement are presented. [1] M. Hino, et al., Physica B 385-386 (2006) 1187. Development of large-m polarizing neutron supermirror fabricated by using ion beam sputtering instrument at KURRI. [2] R. Maruyama, et al., J. Appl. Phys. 111 (2012) 063904. Effect of Si interlayer on the magnetic and mechanical properties of Fe/Ge neutron polarizing multilayer mirrors.

57

A12

High Precision Depolarization Measurements in Polarizing Supermirrors Christine Klauser1,2, Thierry Bigault1, Jérémie Chastagnier1, David Jullien1, Pascal Mouveau1, Alexandr Petoukhov1, Natalyia Rebrova3, Torsten Soldner1 1Institut Laue-Langevin, Grenoble, France 2 Technische Universität Wien, Austria 3 Universität Heidelberg, Germany We present an opaque test bench for neutron depolarization studies and first results on polarizing supermirrors. It consists of two opaque 3He cells with in-situ adiabatic fast passage flipping of the helium spin. The test bench has been validated to work at an accuracy of 10-4 relative at the cold neutron beam PF1B of ILL, for wavelengths ranging from 4 Å to 8 Å. In a beam initially polarized to 99.98 %, depolarization of the order of 10-2 is evident after a single reflection on a polarizing supermirror. Depolarization could be minimised though not completely avoided when working at high magnetizing fields (~0.8T). The data also suggests a correlation between m-value of the supermirror and depolarization, as well as influences from the atomic structure of the reflecting material.

A13

Magnetic anisotropy of the Kondo lattice system CePd1-xRhx

P. Schmakat

1,2, M. Schulz

2, V. Hutanu

4, M. Brando

3, C. Geibel

3, M. Deppe

3, C. Pfleiderer

1, P. Böni

1

1. Physik-Department E21, Technische Universität München, D-85748 Garching, Germany 2. Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), D-85748 Garching, Germany 3. Max-Planck-Institut für Chemische Physik fester Stoffe, D-01187 Dresden, Germany 4. RWTH Aachen, Institut für Kristallographie, D-52056 Aachen The Kondo lattice system CePd1-xRhx undergoes a quantum phase transition as a function of Rh content where ferromagnetism is continuously suppressed. The curvature of the phase boundary TC(x) changes sign for x=0.60. When lowering the transition temperature by substituting Pd by Rh content, a cluster glass phase emerges in the tail region of the phase diagram. We have investigated a single crystal of CePd1-xRhx with x=0.40 using a 3He cryostat on the instrument POLI-HEIDI. In this study we have cooled down the sample in zero magnetic field and recorded the polarization matrix for several temperatures below and above TC. We found that the single crystal with x=0.40 shows significant magnetic anisotropy, supporting the Ising-like character predicted through magnetisation measurements. The magnetic anisotropy can be directly visualized using the 3D spin manipulation option of the instrument POLI-HEIDI. To illustrate this, we show nutator scans at different temperatures. [1] T. Westerkamp et al., Phys. Rev. Lett. 102 (2009) 206404. “Kondo-Cluster-Glass State near a Ferromagnetic Quantum Phase Transition” [2] J. G. Sereni et al., Phys. Rev. B 75 (2007) 024432. “Ferromagnetic quantum criticality in the alloy CePd1−xRhx” [3] C. Pfleiderer et al., J. Low Temp. Phys. 161 (2010) 167-181. “Search for Electronic Phase Separation at Quantum Phase Transitions“

58

A14

Crystal Structure and magnetic properties of the bis tetrapropylammonium

Hexachlorodicuprate(II): [N(C3H7)4]2Cu2Cl6

Ikram DHOUIB1, Zakaria ELAOUD1, Philippe GUIONNEAU2, Stanislav PECHEV2, Corine Mathonière2

and Tahar MHIRI

1Laboratoire de l’Etat Solide, Département de chimie, Faculté des Sciences de Sfax, BP1171 route sokra, km 3,5, 3000, Sfax, Université de Sfax, Tunisia e-mail :zakaria_elaoud@yahoo.com

2Institut de Chimie de la Matière Condensée de Bordeaux-ICMCB, 87 av Dr A; Schweitzer, 33608 Pessac Cedex-France

The large structural variability of Cu (II) due to the presence of an active Jahn–Teller effect in the d9 electronic system and the relative flatness of the potential surfaces make the thermochromism in chlorocuprates of continual interest. These compounds and their properties are of interest not only in inorganic chemistry but also in fields ranging from solid-state physics to bioinorganic chemistry. Among solid-state physicists and chemists, there is a great interest in the copper (II) halides owing to the plasticity of the metal coordination sphere which leads to a great variety of crystalline architectures with different coordination numbers, geometries and nuclearties, and makes copper systems excellent candidates for analysing correlations between structural parameters and magnetic properties [1]. Single crystals of the novel, of bis tetrapropylammonium hexachlorodicuprate (II) [N(C3H7)4]2Cu2Cl6 , were grown by slow evaporation solution technique at room temperature. The compound was characterised by IR, differential thermal analysis (TG-DTA), single crystal X-ray diffraction and temperature dependent magnetic susceptibility. The latter crystallizes in the triclinic system (space group P-1, Z = 2) with the following unit cell dimensions: a = 9.3851(2)Ǻ , b = 9.3844(2)Ǻ , c = 11.8837(3)Ǻ , α = 106.333(1)°, β = 100.028(1)° and γ = 113.283(1)°. Besides, its structure was solved using 5526 independent reflections down to R = 0.043. The atomic arrangement can be described by alternating organic and inorganic layers parallel to the (101) plan, made up of tetrapropylammonium groups and Cu2Cl6 dimers, respectively (Fig.1). In crystal structure, the inorganic layers, built up by Cu2Cl6 dimers, are connected to the organic ones through hydrogen bonding C-H…Cl and van der Waals interaction in order to build cation–anion–cation cohesion [2]. These interactions cause to the formation of a three-dimensional supramolecular architecture, in which they may be effective in the stabilization of the crystal structure. The temperature dependence of the magnetic susceptibility was measured in the temperature range of 1.8 and 300 K at different magnetic field intensities. The experimental effective magnetic moment coincides with theoretical one. The results indicate that the complex exhibit weak antiferromagnetic coupling between the copper (II) centers [3]. [1] P. Roman, J. Sertucha, A. Luque, L. Lezama, T. Rojo, Polyhedron 15 (1996) 1253–1262. [2] G. Lach, L. Laskowski, I.V. Kityk, V. Kapustianyk, V. Rudyk, Ya. Shchur, S. Tkaczyk, J. Swiatek, M. Piasecki, J. Non-Crystalline Solid 353 (2007) 4353. [3] Chow C., Inorg. Chem. 14 (1975 ) 205.

59

A15

SNP@PSI: experiments performed with MuPAD at the Paul Scherrer Institut

Amy Poole

1, Bertrand Roessli

1, Peter Babkevich

2, Andrew Boothroyd

2, Jonathon White

1, Michel Kenzelmann

3, Tom

Fennell1

1. Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen, PSI, Switzerland 2. Department of Physics, Oxford University, Oxford, OX1 3PU, United Kingdom

3. Laboratory for Development and Methods, Paul Scherrer Institut, CH-5232 Villigen, PSI, Switzerland

This poster will give an overview of recent experiments that have been completed with the MuPAD spherical neutron polarimetry (SNP) set-up on the TASP triple axis spectrometer, at the Paul Scherrer Institut, Switzerland. [1] Polarised neutron experiments allow the measurement of the interference terms between magnetic and nuclear scattering as well as between the different components of the magnetic interaction vector, M

⊥⊥⊥⊥

. These terms allow the separation of a weak magnetic signal from a large amount of nuclear scattering and/or the measurement of the change in the intensity due to scattering from real and imaginary components of M

⊥⊥⊥⊥

. [2] Tb2Ti2O7 is an example of the former application whereby MuPad was used to confirm the elastic/inelastic contributions to diffuse scattering measurements made on an energy-integrating instrument. [3] The latter application is demonstrated with the magnetic structure determination and domain population measurements of the type-two, spin spiral multiferroic materials Mn2GeO4 and CuO. [4, 5] References [1] M Janoschek, S Klimko, R Gaehler, B Roessli, P Boeni, Physica B 397 (2007) 125 [2] F Tasset, PJ Brown, E Lelievre-Berna, et al Physica B, 267 (1999) 69 [3] T Fennell, M Kenzelmann, B Roessli, M K Haas, R. J. Cava, submitted [4] J S White, T Honda, K Kimura, et al PRL 108 (2012) 077204 [5] P Babkevich, A Poole, R D Johnson, B Roessli, D Prabhakaran, A T Boothroyd, PRB, accepted A16

Polarized SANS study of spatially ordered arrays of interacting nanowires

N. A. Grigoryeva

1, S. V. Grigoriev

2, K. S. Napol’skii

3, A. P. Chumakov

2, A. A. Eliseev

3, I. V. Roslyakov

3, H.

Eckerlebe4, and A. V. Syromyatnikov

2

1St. Petersburg State University, St. Petersburg, 198504 Russia

2Petersburg Nuclear Physics Institute, Gatchina, Saint-Petersburg, 188300, Russia

3Moscow State University, Moscow, 119991 Russia

4Helmholtz_Zentrum Geesthacht, Geesthacht, 21502 Germany

Magnetic properties of spatially ordered arrays of interacting nanowires have been studied by means of small–angle diffraction of polarized neutrons. Several diffraction maxima or rings that correspond to the scattering of the highly ordered structure of pores/wires with hexagonal packing have been observed in neutron scattering intensity maps. The interference (nuclear–magnetic) and pure magnetic contributions to the scattering have been analyzed during the magnetic reversal of the nanowires array in a field applied perpendicular to the nanowire axis. The average magnetization and the interference contribution proportional to it increase with the field and are saturated at H = HS. The magnetic reversal process occurs almost without hysteresis. The intensity of the magnetic contribution has hysteresis behavior in the magnetic reversal process for both the positive and negative fields that form the field dependence of the intensity in a butterfly shape. It has been shown that this dependence is due to the magnetostatic interaction between the filaments in the field range of H ≤ HS. A theory for describing the magnetic properties of the arrays of interacting ferromagnetic nanowires in the magnetic field has been proposed.

60

A17

Spatially Ordered Magnetic Nanowires investigated by Polarized SANS

Thomas Maurer, Fatih Zighem, S. Gautrot, Frédéric Ott, Grégory Chaboussant

Laboratoire Leon Brillouin, UMR12 CEA-CNRS, F-91191 Gif sur Yvette, France L. Cagnon, O. Fruchart

Institut Néel, UPR 5031, 25, Avenue des Martyrs F-38049 Cedex 9 Grenoble, France The structural, magnetic and optical properties of nano-objects organized in periodic arrays have been intensively studied in the recent years, as part of the growing interest, both scientifically and technologically, for functionalized nanostructures. Many experimental techniques have been developed to probe the properties of nanomaterials. The first approach consists in studying the properties of nanomaterials in the direct space (microscopy). However, in this approach, the information remains local and, in order to probe assemblies of nano-objects, studying the properties of materials in the reciprocal space seems an appealing alternative (Raman spectroscopy, X-ray scattering and neutron scattering). SANS in particular allows probing a large range of nanosystems and giving access to both static and dynamic properties. We present a polarized SANS study of ferromagnetic Co nanowires (40 nm diameter) included in porous Al2O3 membranes with about 100nm inter-nanowire distances. Both the structural and magnetic properties of such arrays of nanowires have been investigated under magnetic field in the whole hysteresis cycle. We show that the magnetic contribution to the total SANS signal cannot be explained without considering demagnetizing fields and neighbouring nanowires [1]. [1] Th. Maurer et al, in preparation (2012).

A18

The transition from magnetic Coulomb phase to Higgs phase in the quantum spin ice Yb2Ti2O7

L. J. Chang, S. Onoda

1, Y. Su2, Y. –J. Kao

3, Y. Yasui

4

Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan ljchang@mail.ncku.edu.tw, 1Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan

2Jülich Centre for Neutron Science JCNS-FRM II, Forschungszentrum Jülich GmbH, Outstation at FRM-II, Lichtenbergstrasse 1, D-85747 Garching, Germany

3Department of Physics, National Taiwan University, Taipei 10607, Taiwan 4Department of Physics, Division of Material Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,

Japan Polarized neutron-scattering experiments had been carried out on single crystal Yb2Ti2O7 in a 3He-dilution refrigerator from 1.5 K to 0.04 K. The results reveal that the diffuse [111]-rod scattering [1] is suppressed below Tc ~ 0.21 K, where magnetic Bragg peaks and a full depolarization of neutron spins are observed with the thermal hysteresis, indicating a first-order ferromagnetic transition. The transition from magnetic Coulomb phase to Higgs phase in a quantum spin-ice model [2] is adapted to explain the consequences. Pinch points are observed in both experimental and theoretical results to suggest its quantum spin ice state. This has been understood theoretically from an effective classical model where <111> Ising moments, i.e., pseudospin-1/2 interact mainly through a magnetic dipolar interaction [3], showing anisotropic and power-law decaying dipolar spin correlations [4]. [1] K. A. Ross et al., Phys. Rev. Lett. 103, 227202 (2009). [2] L. J. Chang et al., arXiv: 1111.5406. [3] S. T. Bramwell and M. J. P. Gingras, Science 294, 1495 (2001). [4] S. V. Isakov et al., Phys. Rev. Lett. 93, 167204 (2004).

61

A19

High-resolution neutron Larmor diffraction for phase transition studies of LaAlO3

J. Repper

a, T. Keller

b,c, W.W. Schmahl

d

aPaul Scherrer Institut, Materials Science and Simulation, NUM/ASQ, 5232 Villigen PSI, Switzerland bForschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), TU München, Lichtenbergstr. 1, 85747 Garching, Germany

cMax-Planck-Institut für Festkörperphysik, Heisenbergstr. 3, 70569 Stuttgart, Germany dLehrstuhl für anorganische und biogene Geomaterialien, LMU München, Theresienstr. 41, 80333 München, Germany

Neutron Larmor diffraction (LD) is a high-resolution diffraction technique (∆d/d=10-6) based on the Larmor precession of polarized neutrons. The basic principle of the LD technique is to mark each single neutron by a Larmor precession phase such that the phase f only depends on the lattice spacing d and is independent of the Bragg angle or the velocity of the single neutron. However, the number of Bragg reflections hit the detector area influences the signal. The deconvolution of two superposed lattice spacing information is challenging, since often the scattering fractions are not known. LaAlO3 is a rhombohedral perovskites often used as substrate material for superconducting or ferroelectric thin films and possesses a rhombohedral-cubic phase transition temperature of approx. Tt = 813 K. In the low-temperature phase some Bragg reflections of the cubic phase split, e.g. (220) in (220)+(208), others not (e.g. (020)). In this study we followed the phase transition, and thus the splitting of Bragg reflections, in-situ by neutron Larmor diffraction. Thermal expansion and peak splitting are in the focus of this study. A20

Skew scattering of cold unpolarized neutrons in ferromagnetic crystal

Udalov Oleg

Institute for Physics of Microstructures RAS, (603950) GSP-105, Nizhny Novgorod, Russia, udalov@ipmras.ru The problem of neutron scattering by a single magnetic atom is theoretically considered in the second order perturbation theory. It is demonstrated that the elastic scattering of unpolarized neutron by a magnetic atom is skewed, i.e., it contains a term including the symmetry of a mixed product of the atom magnetic moment and the wave vectors of incident and scattered neutrons )]'([ hkk ⋅× . The problem of dynamical diffraction of unpolarized neutrons by a perfect ferromagnetic crystal is investigated. We consider the case when the Bragg condition is satisfied for two reciprocal lattice vectors. In this situation the neutron skew scattering manifests itself as a dependence of the diffracted beam intensity on the sign of the crystal magnetization. The diffraction of unpolarized neutrons by a Dy crystal has been calculated. The change in the intensity through the magnetization reversal in this case is estimated at 50%.

62

A21

Observation of ferromagnetic correlation caused by 3d admixture in nonmagnetic material by means of small-

angle polarized neutron scattering

V. Runov, D. Ilyin, M. Runova, A. Radzhabov

Petersburg Nuclear Physics Institute (PNPI), 188350, Gatchina, Russia e-mail: runov@pnpi.spb.ru

We discuss possibility of studying ferromagnetic correlation, caused by 3d metal admixture in nonmagnetic matrix. As example, the results of measuring polarization and magnetic-nuclear interference got from analysis small-angle polarized neutron scattering in alloy CuZn(20) with admixture Ni (1ат.%). It was shown that Ni are clustered in CuZn matrix with typical correlation radius 100 < Rc < 5000 Ǻ depending on thermal treatment of the sample. The type of cross-correlator, defining magnetic-nucleus interference, is satisfactorily described by exponential law exp(-r/Rc), where r is a distance. It was found that nonmagnetic CuZn(20) matrix with nearly uniform statistical distribution of 1% Ni possesses metamagnetic properties in magnetic field H ≈ 0.5 T at room temperature. Possibility of studying ferromagnetic correlation, caused by vacancies in nonmagnetic matrix are discussed too. A22

Larmor labeling methods: Neutron Resonance Spin Echo spectroscopy beyond standard line width measurements

Felix Groitl

1, Katharina Rolfs

1, Diana Quintero-Castro

1, Klaus Kiefer

1,

Thomas Keller2, 3

, Klaus Habicht1

1Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, 14109 Berlin, Germany, felix.groitl@helmholtz-berlin.de

2Max-Planck-Institute for Solid State Research, Heisenbergstraße 3, 70569 Stuttgart, Germany 3FRM II, Lichtenbergstraße 1, 85748 Garching, Germany

We explore new territory for Neutron Resonance Spin Echo (NRSE) spectroscopy beyond measuring lifetimes of elementary excitations and present two experiments which benefit from the high resolution offered by this method. The first experiment aims at separating modes split in energy which are difficult to resolve with standard neutron scattering techniques [1]. In this context it is essential to take violation of the spin echo conditions and arbitrary local gradients of the dispersion surface into account which we provide with an extended model of the NRSE resolution function [2]. The second class of experiments deals with line shape analysis relevant for the phenomenon of asymmetric line broadening [3]. Measurements were performed on Cu(NO3)2⋅2,5D2O, a model material for a 1-D bond alternating Heisenberg chain, and on Sr3Cr2O8, a dimerized spin-1/2 antiferromagnet. This is the first time this effect has been measured with high-resolution NRSE. The particular advantage of the NRSE method is the direct access to the line shape since there is no convolution of the signal with the resolution function of the spectrometer. Our experimental results show clear evidence for double peaked line shapes rather than a continuous asymmetry. References [1] F. Groitl et al., Physica B 406 12 2342-2345 (2011) [2] K. Habicht et al., Physica B 350 E803-806 (2004) [3] D. A. Tennant et al., Physica Review B 85 1 014402 (2012)

63

A23

Magnetic anisotropy in the interface of Fe3O4/Mn3O4 superlattices probed by neutron reflectivity

Chin Shan Lue1, L. J. Chang

1,2, M. Takeda

3, C. H. Lee

2, G. Chern

4

1Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan, cslue@mail.ncku.edu.tw

2Department of Engineering and System Science, National Tsing Hua University, HsinChu 30013, Taiwan 3 Quantum Beam Science Directorate, JAEA, Tokai, Ibaraki 319-1195, Japan

4 Department of Physics, National Chung Cheng University, Chia-Yi 621, Taiwan

Fe3O4 and Mn3O4 both have spinel structure and some physical similarities. However, Fe3O4 is well known to show the

Verwey transition, while Mn3O4 shows ferrimagnetism and substantially high magnetic anisotropy. The magnetic

anisotropy Fe3O4/Mn3O4 superlattices is thus expected to possess highly magnetic anisotropy, and to have an effect on

the antiparallel state (spin–flop phase) and compensation point. High quality Fe3O4/Mn3O4 superlattices grown on

MgO [110] have been prepared by molecule-beam epitaxy, and characterized by in-situ reflection high-energy electron

diffraction and ex-situ x-ray diffraction. We will report polarized neutron reflectivity results on Fe3O4/Mn3O4

superlattices for the temperature range cross both Fe3O4 and Mn3O4 transitions to investigate the anisotropy and

magnetic configuration around the compensation point of the system.

A24

Field-induced magnetism in super-oxygenated (La,Sr)2CuO4+y

S.L. Holm1, L. Udby

1, J. Larsen

2, N.B. Christensen

2, S.B. Emery

3, Y.F. Nie

3,

N.H. Andersen2, J.-G. Grivel

2, Ch. Niedermayer

4, B.O. Wells

3, and K. Lefmann

1

E-mail: sonja@fys.ku.dk 1Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Denmark

2Materials Science Division, Risø-DTU, Roskilde, Denmark 3Department of Physics, University of Connetticut, USA

4Laboratory for Neutron Scattering, Paul Scherrer Institute, Switzerland

The super-oxygenated (La,Sr)2CuO4+y (LSCO+O) may be a key to understanding the complex interplay between superconducting and magnetic phases in the cuprate high-Tc super-conductors [1]. Earlier studies of LSCO+O suggests that the system performs an electronic phase separation into a) a magnetically ordered phase, resembling the “1/8” phase of the oxygen-stoichiometric (La,Sr)2CuO4 (LSCO), and b) a near-optimally doped superconductor [2].

We have produced a new, large single crystal sample of LSCO+O, with a Tc of 38.5 K, similar to optimally doped LSCO. In contrast to all other LSCO+O samples investigated to date, muon spin rotation shows no signature of static magnetic order. Neutron diffraction, however, shows a field-induced signal from magnetic long-range 1/8-order, as seen in LSCO [3], but this signal vanishes in the limit of zero field. In near-optimally doped LSCO samples, similar behavior has been found, but with a field-offset before appearance of the static magnetic signal [4,5]. This could suggest that our system is right at the quantum critical point in the phase diagram of field-induced magnetism [6].

References [1] B.O. Wells et al., Z. Phys. B 100, 535 (1996) [4] B. Khaykovich et al., PRB 71, 220508 (2005) [2] H.E. Mohottala et al., Nature Materials 5, 377 (2006) [5] J. Chang et al., PRL 102, 177006 (2009) [3] B. Lake et al., Science 291, 1759 (2001) [6] E. Demler et al, PRL 87, 067202 (2001) Work at Univ. Conn. supported by USDOE-BES under grant DE-FG02-00ER45801.

64

A25

Waveguide-enhanced polarized neutron reflectometry: a new approach in the study of magnetic proximity

effects

Yu.N. Khaydukov1,2

R.O. Tsaregorodsev2, B. Nagy

3, L. Bottyán

3, Yu.V. Nikitenko

4, V.L. Aksenov

4

1 Max Planck Institute for Solid State Research, Stuttgart, Germany 2 M.V. Lomonosov Moscow State University, Moscow, Russia

3 KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary 4 Joint Institute for Nuclear Research, Dubna, Russia

A number of intriguing physical phenomena are related with superconducting/ferromagnetic (S/F) heterostructures, where proximity effects can cause modification of superconducting and magnetic parameters. Study of such systems is the challenge for PNR as pronounced effects are small and/or number of proximity interfaces is restricted. In this paper we propose a new sensitive approach on the base of the use of waveguide enhancement of the intensity of magnetic scattering (spin-flip, diffuse or inelastic scattering). Polarized neutron reflectometry was used to study the magnetic proximity effect in a superconductor/ferromagnet (SC/FM) system of composition Cu(32nm)/V(40-80nm)/ FM(dFM)/MgO (FM: Fe, Ni, dFM = 1, 4 nm). In contrast to previous studies in the literature, here a single SC/FM bilayer is studied and possible multilayer artifacts are excluded. The necessary signal enhancement is achieved by waveguide resonance, i.e. preparing the SC/FM bilayer sandwiched by the highly reflective MgO substrate and Cu top layer, respectively. Change of the magnetic scattering intensity was observed for several samples below T . Different models of proximity effects explaining observed changes are

65

Poster Session B, Wednesday, July 04th 2012

B01

Wavelength-selected neutron pulses formed by a spatial magnetic neutron spin resonator

Christoph Gösselsberger, Gerald Badurek, Erwin Jericha, Sebastian Nowak

Vienna University of Technology, Atominstitut, Wien, Austria, goesselsberger@ati.ac.at We present a novel type of spatial magnetic neutron spin resonator for precise wavelength-selection and definition of the time structure of thermal and cold neutron beams. This device exploits the fact that upon passage of polarised neutrons through a spatially alternating transverse static magnetic field each neutron in its rest frame experiences an alternating field with a frequency depending on the neutron velocity and the spatial period of the resonator. If this frequency equals the Larmor precession frequency a resonant spin flip will take place. This property is used to pick out a desired wavelength band of adjustable width from an initially polychromatic neutron beam. The time structure of this neutron beam can be tailored from continuous operation to ultra-short pulses in the microsecond regime by application of a travelling magnetic wave mode. Thus, this new type of pulsed neutron magnetic spin resonator may be useful for polarised neutron beamlines both at continuous as well as short- and long-pulse spallation sources. It is of clear advantage that the time structure of neutron pulses produced by this method will be almost arbitrarily adjustable by purely electronic means. To demonstrate the feasibility of this technique, we designed and engineered a first prototype consisting of ten individually ultra-fast switchable aluminium stages for the generation of neutron pulses in the microsecond regime [1]. This resonator was installed at a polarised neutron beamline at the 250 kW TRIGA reactor of the Vienna University of Technology at the Atominstitut. Here we report on the results of a first test of this new type of magnetic neutron spin resonator. References: [1] C. Gösselsberger et al., J. Phys.: Conf. Ser. 340 (2011) 012028. Neutron beam tailoring by means of a novel pulsed spatial magnetic spin resonator.

B02

KOMPASS – the new three-axes-spectrometer with 3D spherical polarization analysis to-be at FRM-II

Alexander GRÜNWALD

1, A.C. Komarek

2, S. Giemsa

1, P. Böni

3, M. Braden

1

1: Institute of Physics II, University of Cologne, 50937 Cologne / Germany 2: Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden / Germany

3: Lehrstuhl für Experimentalphysik E21, Techn. Universität München, 85748 Garching / Germany KOMPASS, the new, cold neutron three-axes-spectrometer to-be installed at the FRM-II, is fully designed to work exclusively with polarized neutrons and to provide a zero-field 3D spherical polarization analysis. The instrument is therefore dedicated to study all types of magnetic ordering and excitations in crystalline structures. Besides a global presentation of the instrument design, here we will focus on the highlight of the instrument – the state-of-the-art polarizing and parabolically focusing guide system concept, which is expected to provide high polarization rates and superior flexibility with respect to the resolution in energy over the conventionally straight, or elliptical, guide systems [1]. References [1] A.C. Komarek, P. Böni, M. Braden, Nucl. Instr. and Meth. A 647 (2011) 63-72. This project is supported by the German Federal Ministry of Education and Research (BMBF) by project 05KN7PK1 & 05K10PK1.

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B03

Precise magnetic field mapping for the 3He neutron spin filter

T. Ino

1, Y. Arimoto

1, H. Kira

2, Y. Sakaguchi

2,

T. Shinohara3, K. Sakai

3, T. Oku

3, K. Kakurai

3, K. Ohoyama

4

1KEK, Tsukuba, Ibaraki 305-0801, Japan, takashi.ino@kek.jp 2CROSS, Tokai, Ibaraki 319-1106, Japan

3JAEA, Tokai, Ibaraki 319-1195, Japan 4IMR, Tohoku University, Sendai, Miyagi 980-8577, Japan

The 3He neutron spin filter requires a homogeneous magnetic field, otherwise the nuclear polarization of 3He gas will easily be lost by small magnetic field gradients. Magnetic cavities with their field gradients of 10-4/cm or better are often in demand, and many such cavities - Helmholtz coils, solenoids, magic boxes, etc - have been developed. It is, however, not so common to compare the design and actual magnetic fields for those cavities because measuring the magnetic field with a precision better than 10-4 is not so easy. In addition, the environmental magnetic field or the stray field should affect the magnetic cavities, and the actual fields may be quite different from those by simulations, especially at the neutron beamlines where magnetic materials, mostly iron, are everywhere. In many cases, one checks the field homogeneity by measuring the spin relaxation time of polarized 3He gas, T1 and/or T2. It is more convenient to realize higher homogeneities if the magnetic field can directly be measured, and we have developed a compact proton magnetometer to make a field mapping for the magnetic cavities of the 3He neutron spin filter. The sensor of the magnetometer is as small as 1 cm and has a precision of several ppm at 2mT, which is accurate enough for our purpose. As a demonstration of the magnetometer, we have made a three dimensional field mapping for a solenoid magnetic cavity to compare with the simulation.

B04

Polarisation Analysis Neutron Chopper Spectrometer, POLANO, at J-PARC

K. Ohoyama, T. Yokoo1,2, S. Itoh1,2, J. Suzuki1, K. Iwasa3, K. Tomiyasu3, M. Matsuura, H. Hiraka, M. Fujita, H. Kimura4, H. Kira5, Y. Sakaguchi5, T. Ino1,2, T. Oku6, Y. Arimoto1, T. Sato, T.J. Sato7, K. Kaneko6, J. Suzuki5, H.M. Shimizu1,8, T. Arima9, M. Takeda6, M. Hino10, S. Muto1,2, H. Nojiri

IMR, Tohoku Univ. Sendai 980-8577, Japan, ohoyama@imr.tohoku.ac.jp 1KEK, Tsukuba 305-0801, Japan, 2J-PARC Center, Tokai, 319-1195, Japan, 3Graduate School of Science, Tohoku Univ., Sendai

980-8578, Japan, 4IMRAM, Tohoku Univ. Sendai, 980-8577, Japan, 5CROSS, Tokai, 319-1106, Japan, 6JAEA, Tokai, 319-1195, Japan, 7ISSP, U. Tokyo, Tokai, 319-1195, Japan, 8Graduate School of Science, Nagoya Univ. Nagoya 464-8602, 9Dept. Adv.

Mat. Sci., Univ. Tokyo, Kashiwa, 277-8561, Japan, 10KUR, Kyoto Univ. Kumatori, 590-0494, Japan

We aim at constructing a polarisation analysis spectrometer in J-PARC based on a collaboration of KEK and Tohoku Univ., which will be indispensable for investigations of spin correlations in multipolar ordering materials, high-TC superconductors, multiferroic materials and so on. The proposed instrument, named POLANO, is designed as a compact chopper spectrometer with a rotary detector bank (L1=17.55m, L2=2.5m) installed at a decoupled H2 moderator of J-PARC/MLF. To realise experiments with Ei>100meV, direct guide tubes with ellipsoid focusing will be adopted. As a main polariser, a SEOP 3He spin filter will be used. The expected polarised beam flux at the sample is ~1.2E+5 (n/sec/cm2/meV/MW) at E=100meV for an optimised SEOP condition. We have already succeeded in polarised neutron diffraction experiments with a SEOP 3He filter for E=24meV in JRR-3. At the first phase of the project, we will concentrate the Ei, Ef <30meV region using a fan type bender supermirror analyser because rich scientific targets exists in this region. A V-shape supermirror polariser can be used for experiments with superconducting magnets in this region. As an ambitious challenge, we are considering to adopt cross correlation method for this project. In the second phase, we will try to install a 3He spin filter analyser for the Ef≧100meV region. This project passed in the final board of J-PARC on SEP-2011, and the construction has been authorised.

67

B05

Development of a Polarised Neutron Diffraction System with a 3He Spin Filter on a Powder Diffractometer in JRR-3

K. Ohoyama, K. Tsutsumi1, T. Ino

2, H. Hiraka, Y. Yamaguchi, H. Kira

3, T. Oku

4, Y. Sakaguchi

3, Y. Arimoto

2, W. Zhang, H.

Kimura, K. Iwasa1, M. Takeda

4, J. Suzuki

3, K. Yamada

5, K. Kakurai

4

IMR, Tohoku Univ. Sendai 980-8577, Japan, ohoyama@imr.tohoku.ac.jp 1Graduate School of Science, Tohoku Univ., Sendai 980-8578, Japan,

2KEK, Tsukuba 305-0801, Japan, 3CROSS, Tokai, 319-1106, Japan, 4JAEA, Tokai, 319-1195, Japan, 5AIMR-WPI, Tohoku Univ. Sendai, 980-8577, Japan

We have constructed a polarised neutron diffraction (PND) instrument on an angular dispersive powder diffractometer, HERMES, in JRR-3, Japan, using a transportable 3He spin filter (SF) neutron polariser without optical pumping. We also developed a compact non-adiabatic two-coil spin flipper (Drabkin type) for thermal neutrons for this system. In the system, an identical cylindrical SF cell (220kPa, 30mm*50mm, GE180) was used. Note that, for every experiment, the SF cell was transported from a SEOP filling station in KEK to HERMES by car for ~2h. During the transportation and experiments, the SF cell was kept in a homogeneous magnetic field in a solenoid coil. Typical values of 3He and neutron (=1.84Å) polarisation at the beginning of experiments on HERMES were PHe=0.67(2) and Pn=0.66(4), respectively. Note that the obtained PHe is close to a typical value (~0.7) in the filling station. PHe decayed exponentially during experiments because the SF was operated without optical pumping; the decay time of PHe of 120~150hr was stably obtained in the experiments, which is longer than a typical measurement time (~10hr). Using the PND system on HERMES, we succeeded in performing flipping difference measurements of ferromagnetic application magnets. These results indicate that the transportable SF approach in this system worked quite well, so that SFs can be used in most of the instruments at J-PARC and JRR-3.

B06

Monte-Carlo simulations for the optimization of a MIEZE spin-echo instrument at the ESS

Georg Brandl

1,2, Tobias Weber

2, Wolfgang Häußler

1,2, Robert Georgii

1,2, Peter Böni

2

1 Forschungsneutronenquelle Heinz Maier-Leibnitz, Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany (georg.brandl@frm2.tum.de)

2 Physik Department E21, Technische Universität München, James-Franck-Str., 85748 Garching, Germany

The upcoming European Spallation Source ESS will combine an unprecedented peak neutron flux with a long-pulse beam structure, which are parameters ideally suited for neutron spin echo [1] techniques. We focus here on the study of a spectrometer using the MIEZE (Modulation of IntEnsity by Zero Effort) principle using the NRSE technique [2], because with MIEZE all beam preparation can be performed before and/or close to the sample thus allowing measurements with depolarizing samples and sample environment and/or a wide angular range, respectively. We present work on Monte-Carlo simulations and optimizations for MIEZE-type instruments using the McStas software package. In particular, we quantitatively describe the effects of various imperfections on the polarization, for example due to coil inhomogeneities or sample—detector path length differences in MIEZE [3], and discuss possible remedies in terms of an optimized geometry of the samples or correction coils.

References [1] F. Mezei, Z. Phys. A 255 (1972) 146. Neutron spin echo: A new concept in polarized thermal neutron techniques. [2] R. Golub and R. Gähler, Phys. Lett. A 123 (1987) 43. A neutron resonance spin echo spectrometer for quasi-elastic and inelastic scattering. [3] G. Brandl, R. Georgii, W. Häußler, S. Mühlbauer and P. Böni, Nucl. Inst. Meth. A 654 (2011) 394. Large scales–long times: Adding high energy resolution to SANS.

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Figure 1: Non-spin flip and spin-flip diffraction patterns from powdered Si.

B07

Initial Results of Uniaxial Polarisation Analysis on the WISH Diffractometer

J.G.Donaldson1, S.Boag

1, P.Manuel

1, J.R.Stewart

1, J.W.Taylor

1

1ISIS, STFC, Rutherford Appleton Lab, Didcot, Oxfordshire, UK, Joe.Donaldson@stfc.ac.uk

We report initial results using the polarization analysis insert, Zoolander [1], on the WISH time-of-flight diffractometer at ISIS. This insert enables uniaxial polarisation analysis, utilizing a neutron spin filter(NSF) polariser/flipper [2] and NSF analyser, held within a single magnetic field provided by a optimised four coil Barker set. The arrangement was used to extract flipping ratios from measurements of powdered Si establishing the polarisation of the beam as a function of time. Initial flipping ratios of up to 20 were achieved. The data collected were corrected to account for the finite polarisation of both the polariser and analyser NSF allowing a separation of coherent and incoherent scattering to be achieved. A discussion of future developments of the system is also presented. References [1] T.J. McKetterick et al, Physica B 406 (2011) 2436-2438. Optimised adiabatic fast passage spin flipping for 3He neutron spin filters. [2] C.J. Beecham et al, Physica B 406 (2011) 2429-2432. 3He polarization for ISIS TS2 phase I instruments.

B09

Using Light to see Neutrons: a New 2D-Detector with High Resolution at the Lab. Léon Brillouin

P. Baroni, L. Noirez, G. Exil, A. Laverdunt Laboratoire Léon Brillouin (CEA-CNRS), Ce-Saclay, 91191 Gif-sur-Yvette Cédex, France

A new position sensitive detector (PSD) built at the Laboratoire Léon Brillouin is now available. With 250000 pixels and a 16 bit dynamic range, the Barotron is well adapted for elastic neutron scattering studies. In contrast to conventional gas chamber detectors, this PSD uses a coupling of a photoemission means adapted for the neutron radiation and a cooled low-light level charge-coupled detection (CCD) device. The result is a two-dimensional detector with a large detection area (260 mm x 260 mm), a very low detection threshold (<1 neutron/cm2/s), a true 16 bits dynamic range and a high spatial resolution (0.5 mm x 0.5 mm). This new neutron detector offers a performance which is competitive with those of the best synchrotron equipment in terms of a very detailed and quantitative observation of the reciprocal space.

An exclusive license agreement has been signed by the CEA with the company MAATEL-Scientific Instrumentation

[1] patent n°0502379, 24/03/2005 - PCT [2] L. Noirez, P. Baroni, Applied Physics Letters 90 (2007) 243111.

High resolution 2D neutron scattering pattern produced by a 1mm thick sample of PTFE (Teflon*) stretched along the horizontal direction. PTFE is a semi-crystalline polymer. The pattern indicates that the stretching has induced the orientation of the crystallites.

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B10

Neutron Polarizations in POLANO Project at J-PARC

T. Yokoo, K. Ohoyama1, S. Itoh, S. Ishimoto

2, H. Kira

3, Y. Sakaguchi

3, T. Ino, T. Oku

4, Y. Arimoto, M. Takeda

4, M. Hino

5,

S. Muto

IMSS, High Energy Accelerator Research Organization (KEK) & J-PARC Center, Tsukuba Japan, tetsuya.yokoo@kek.jp 1IMR, Tohoku Univ., Sendai Japan, 2KEK, IPNS, Tsukuba Japan, 3CROSS, Tokai Japan, 4JAEA, Tokai Japan, 5KUR Kyoto

Univ., Kumatori Japan The devices and methods for polarized neutron experiment in POLANO project are now under discussion. POLANO is the project that we plan to construct a new inelastic spectrometer in J-PARC/MLF utilizing polarized neutron for comprehensive material research. We scheduled three steps toward a realization of polarization analysis on inelastic scattering experiments. We target the energy range of up to hw=30 meV with using SEOP station and supermirror analyzer (fan shaped) as a polarizer and an analyzer, respectively, to begin with. In the second phase, we focus on higher energy experiments (0 meV <hw<100 meV) with a large change of its layout. Dynamic nuclear polarization (DNP) technique will be adopted as a polarizer [1], and a large solid angle SEOP/MEOP will be installed as an analyzer. Finally, over 100 meV of transfer energy will be the target, even though it requires a big technical jump to accomplish such a high energy experiment with polarization analysis. It is reported the current R&D status of polarizers, analyzers and related components in POLANO project, also the concept of the spectrometer is discussed. References [1] D. G. Grabb, C. B. Higley, A. D. Krisch, R. S. Raymond, T. Roser, J. A. Stewart and G. R. Court, Physical Review Letters 64 (1990) 37003. Observation of a 96% Proton Polarization in Irradiated Ammonia

B11

Up-Coming Polarised Neutron Capabilities on ANSTO Instruments Using Polarised 3He Neutron Spin Filters

Wai Tung Lee

1, Frank Klose

1, David Jullien

2, Pierre Courtois

2, Ken Andersen

3

1Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia, wtl@ansto.gov.au 2Institute Laue Langevin, Grenoble, France

3European Spallation Source, Lund, Sweden A joint project of the ANSTO and the ILL is underway to put Polarised 3He based neutron spin-filters - polariser and polarization analyser on 6 ANSTO instruments. The instruments include SANS Quokka, diffractometer Wombat, reflectometer Platypus, thermal and cold triple-axis spectrometers Taipan and Sika, and cold neutron time-of-flight spectrometer Pelican. Works are underway to expand their use to Laue diffractometer Koala and new instruments that are being designed and built. A 3He gas polarizing station based on the Metastable Exchange Optical Pumping method [1] is being shipped to ANSTO. It has reached 72% 3He polarization in spin-filter cell at a 1.2 bar-litre production rate. Silicon-window cells with 3He decay time constant T1 up to 300 hours are being incorporated into several instruments. Wide-angle analyser “Pastis” cells [2] will analyse the scattering on the diffractometer and the TOF spectrometer. To house the 3He cells, our works has produced 500mm-long magnetio-static cavities “Magic Boxes” (MB) with T1(MB-only)=400 hours, and “Pastis” uniform field coil with T1(coil-only)=400-1200 hours. We will present the latest development of the project. References [1] G.K. Walters, et al., Phys. Rev. Lett. 8 (1962) 429. [2] K.H. Andersen, et al., Physica B404 (2009) 2652.

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B12

Magnetic shield design of in-situ SEOP polarized 3He neutron spin filter system

H.Kira

1, Y.Sakaguchi

1, J. Suzuki

1, K.Sakai

2, T.Shinohara

2, T.Oku

2, M.Nakamura

2, M.Arai

2, Y.Endo

2, K.Kakurai

2,

Y.Arimoto3, T.Ino

3, H. Hiraka

4, K.Ohoyama

4, H.M. Shimizu

5, L.J. Chang

6

1CROSS, Tokai, Ibaraki 319-1106, Japan, h_kira@cross.or.jp 2JAEA, Tokai, Ibaraki 319-1195, Japan

3KEK, Tsukuba, Ibaraki 305-0801, Japan, 4IMR, Tohoku University, Sendai, Miyagi 980-8577, Japan

5Nagoya Univ., Furocho, Chikusa, Nagoya 464-8602, Japan 6Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan

Polarized 3He gas functions as a neutron spin filter (NSF) and then 3He NSFs have been extensively developed

around the world in recent years. In order to achieve high 3He polarization, a NSF cell must be situated in a homogeneous magnetic field. To make the situation, a magnetic shield is important to screen the polarized gas against environmental stray magnetic fields at neutron beamlines.

Before we have designed a compact, in-situ spin-exchange optical pumping (SEOP) polarized 3He NSF system [1]. To use this NSF system as a neutron beam polarizer at J-PARC and JRR-3, a NSF cell with 10 cm in diameter, 10 cm long and long 3He relaxation time is required. In this study we designed a magnetostatic cavity to satisfy the requirements. The magnetostatic cavity is composed of a main solenoid coil with 25 cm in diameter and 35 cm long and two compensation coils with 12 cm in diameter and 1 cm long, those are surrounded by a double layer magnetic shield made of permalloy B. The calculated 3He relaxation time under 10-gauss stray field is more than 100 hours.

References [1] H. Kira, Y. Sakaguchi, T. Oku, J. Suzuki, M. Nakamura, M. Arai, K. Kakurai, Y. Endo, Y. Arimoto, T. Ino, H.M. Shimizu, T. Kamiyama, K. Tsutsumi, K. Ohoyama, H. Hiraka, K. Yamada, L.-J. Chang, PhysicaB 406 (2011) 2433.

B13

A Polarized 3He Neutron Spin Analyzer for SANS Polarization Analysis

W.C. Chen1,2

, K.L. Krycka1, S.M. Watson

1, Q. Ye

1, T.R. Gentile

1, and J.A. Borchers

1

1National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and 2University of Maryland, College Park, Maryland 20742, USA, wcchen@nist.gov

Supermirrors have typically been used for polarizing well-collimated neutron beams with high polarization and transmission, but their limited angular acceptance makes them impractical for polarization analysis on small-angle neutron scattering (SANS) instruments. We have implemented SANS polarization analysis with 3He neutron spin filters (NSFs) at the NIST Center for Neutron Research for studies of, for example, magnetic nanoparticle assembly [1], multiferroics [2], and giant magnetostriction [3]. Key issues for practical application for NSFs to SANS polarization analysis are sufficient angular coverage, long polarization storage times in the presence of stray fields from strong sample magnetic fields, and the capability to invert the 3He polarization and thus the neutron polarization. We present our recent development in SANS polarization analysis and a survey of scientific applications. Our spin filter analyzers are polarized off-line by spin-exchange optical pumping. Improvements in optical pumping have yielded initial 3He polarization values of 75% - 85%. We will present magnetic field apparatus that allows us to have relaxation time up of 200 hours when a transverse 1.5 T field is applied to the sample. SANS polarization analysis requires accurate knowledge of polarization and spin flip efficiencies. We report determination of these polarization efficiencies, which can be conveniently obtained with a 3He analyzer. Finally we discuss the plan for performing in-situ spin-exchange optical pumping on the SANS instrument. References [1] K. Krycka et al., Phys. Rev. Lett. 104, 207203 (2010). [2] M. Ramazanoglu et al., Phys. Rev. Lett. 107, 207206 (2011). [3] M. Laver et al., Phys. Rev. Lett. 105, 027202 (2010).

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B14

Characterization of Spatial Uniformity of Neutron Polarization for a Polarized 3He Based SANS Spin Analyzer

W.C. Chen

1,2, S.M. Watson

1, K.L. Krycka

1, J.A. Borchers

1, and R. W. Erwin

1

1National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and 2University of Maryland, College Park, Maryland 20742, USA, wcchen@nist.gov

A polarized 3He neutron spin filter (NSF) has been employed or is planned to be employed to spin-analyze the large area and widely divergent scattered beams in small-angle neutron scattering (SANS) in several neutron facilities worldwide. SANS polarization analysis with 3He NSFs has recently been developed at the NIST Center for Neutron Research for studies of magnetic nanoparticle assembly, multiferroics, and giant magnetostriction. These experiments required careful attention to polarization efficiency corrections, which result from the imperfection of the 3He spin filter, supermirror polarizer, neutron spin flipper, and possible spin transport and neutron depolarization from the sample. There is an intrinsic inhomogeneity of the analyzing efficiency due to small spatial variation of the path length of the 3He analyzer. The spin transport efficiency might also vary across the neutron beam. The spatial inhomogeneity in polarization efficiency will be problematic in performing polarization analysis, especially in probing a weak magnetic signal from the sample. We present determination of the overall instrumental polarization efficiency pixel by pixel over a 2-D position sensitive detector by measuring scattering from a strong coherent scatterer in SANS. We have obtained a spatial variation of neutron polarization of 1% for the scattered beams passing through the cell. We present a model for the spatial variation of the path length of the 3He analyzer for the scattered neutron beams. After taking account of the path length spatial variation, we have determined the spin transport loss is negligible for all scattered beams passing through the cell. We plan to incorporate the spatial variations of the efficiencies in the SANS polarization correction software to allow for the detection of even smaller magnetic signals.

B15

First results from Flynn: A new polarized 3He Filling Station

S.Boag1, D.Jullien

2, J.Donaldson

1, S.Marty

2, P.Mouveau

2, J.R.Stewart

1, J. Taylor

1

1ISIS Rutherford Appleton Lab, Didcot, Oxfordshire, OX11 0QX, UK, Stephen.Boag@stfc.ac.uk 2Institut Laue-Langevin, 6 Rue Jules Horowitz, 38042, Grenoble Cedex 9, France

] Polarized 3He can be used as both an effective neutron polarizer and analyser, in the form of Neutron Spin Filter (NSF) cells. 3He gas is traditionally polarized by two methods, metastability-exchange optical pumping (MEOP) and spin exchange optical pumping (SEOP). Building on the success of the TYREX MEOP filling station [1] operational at the ILL, ISIS is now embarking on employing the same technology. This work outlines the production of the new polarized 3He filling station constructed at ILL, and now installed at ISIS, and give details of the main components of the machine. We will also show the performance of the produced polarized gas from time of flight polarization measurement performed at ISIS. The station ‘Flynn’ can fill detachable NSF cells with 3He gas polarized by MEOP. It will be capable of producing gas up to a pressure of 4bars and 3He polarization of 75%, at a rate of at least 1bar-litre per hour. A vertical magnetic field encases the interior set-up in order to maintain polarization levels, it is generated by 6 coils held in place by an outer frame and optimised to give a highly homogenous field. Other components of the machine include 3 Ytterbium fibre lasers, each one polarizing gas in two 3He-filled optical pumping cells, and a piston compressor transferring polarized gas in two stages, first to the buffer cell and then compressed to the required pressure for the NSF cell. References [1] K.H. Andersen et al. Physica B 356 (2005) 103–108

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B16 A new-generation polarised 3He filling station developed at ILL

P. Courtois

1, D. Jullien

1, E. Lelièvre-Berna

1, P. Mouveau

1, A. Petukhov

1

1Institut Laue-Langevin, 6 Rue Jules Horowitz, 38042, Grenoble Cedex 9, France Since the commissioning in 2002 of the polarized 3He filling station Tyrex, ILL has built a set of electronics, tested new optical elements and worked on the electrodes used to polarize the 3He gas with the metastability-exchange optical pumping (MEOP) technique. This has led to huge improvements: the gas is polarized twice as fast as before (1.5 bar-litre per hour) and the maximum polarization available on a neutron beam has risen from 68% to 80%. The total quantity of gas that has been recycled and polarized with Tyrex exceeds 1000 bar-litre (about 1200 cells) and the common production rate reaches 150 bar-litre per year. Following this achievement, ILL has developed and built 2 MEOP filling stations with similar performances for ANSTO and ISIS. More compact, these new stations adopt a vertical design in order to maximize the lifetime of the electric piston compressor. Among many advances, a new release of the control software has been developed to ease the operation and improve further the reliability. We expect to reach 75% of 3He polarization at a rate of at least 1bar-litre per hour. In parallel, we have also designed and constructed new 3He instrument components, such as silicon windowed cells sealed with a new-generation pneumatic valve, a more compact magic box (“MB500”) and a new local filling system. The technical characteristics and the intrinsic performances will be presented in details.

B17

Spin flip chopper using Landau-Zener-Stückelberg Interferometry

Kaoru Taketani

KEK, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan, kaoru.taketani@kek.jp

One can obtain a neutron bunch by using a spin flip chopper, which consists of a RF spin-flipper and a magnetic mirror [1]. The opening time of this chopper cannot be less than the spin-flip time, which is proportional to the amplitude of the RF field from the spin-flipper. Therefore, to obtain smaller opening time, we have to use large amplitude of RF field to rotate neutron spins. However, it becomes difficult to switch on and off the large current to the spin-flipper with high speed. To overcome this problem, we study a Landau-Zener-Stückelberg (LZS) interferometer [2] for neutrons. Its phase shift is proportional to the magnetic field parallel to the neutron spin (p-field) and its beam splitter’s reflectivity can be controlled by the magnetic field perpendicular to the neutron spin (s-field). Because the spin rotation angle is equal to the phase shift of this interferometer, we could reduce the spin-flip time by using a strong and static p-field. On the other hand, we can effectively set the phase shift to zero by switching off the s-field. Because the s-field is not necessarily strong, we can switch on and off the field with high speed. Therefore, we can expect LZS interferometry has a possibility to create a small neutron bunch. To study this possibility, we, as a first step, analysed the spin flip probability through a LZS interferometer that consists of three Helmholtz coils. We will report the details of this analysis. References [1] K. Taketani, et al., Nucl. Instr. Meth. A 634 (2011) S134. A high S/N ratio spin flip chopper system for a pulsed neutron source. [2] S. N. Shevchenko, S. Ashhab, and F. Nori, Physics Reports 492 (2010) 1. Landau–Zener–Stückelberg interferometry

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B18

Design and performance of a cryo-flipper using a YBCO film

S.R.Parnell

1, H.Kaiser

1, F.Li

1, T.Wang

1, D.V.Baxter

1 , W.A.Hamilton

2and R.Pynn

1,2

Department of Physics and Centre for Exploration of Energy and Matter, Indiana University, Bloomington, USA Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee

It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined non-adiabatic magnetic field transition. This can be utilized to produce a highly efficient neutron spin flipper that is suitable for use on a white beam. However, these devices typically utilize niobium and hence require continuous use of liquid helium in order to maintain the device temperature. The use of high Tc materials removes the need for cryogens and has been explored previously [1]. Here we present a design using a 350-nm-thick YBCO film capped with 100 nm of gold on a 78 x 100 x 0.5 mm sapphire substrate (Theva, Germany). We discuss the design and performance of this device. The apparatus is compact (~300 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle He refrigerator. The part of the vacuum chamber, where the YBCO film is located, is ~ 5 cm wide, which allows us to minimize the distance from the film to the magnetic guide fields. This distance is ~30 mm on each side. The details of the guide field design are also discussed. In this design, the maximum neutron beam size that can be used is 45x45 mm2 and we can easily switch from a vertical to a horizontal guide field on either side of the YBCO film. Data are shown for neutron wavelengths between 5-13Å. Acknowledgements: This project is supported by NSF-grant Number DMR-0956741. We would like to acknowledge E.Lelivere-Berna (ILL) for useful discussions on the heat shield construction. References [1] M.R. Fitzsimmons etal., Nucl. Instr. Meth. Phys. Res. A 411, 401 (1998).

B19

Simulations of a neutron spin echo spectrometer and its components using pulsed magnetic fields by VITESS

software package

Raul Victor Erhana,b,*

, Sergey Manoshina,*

, Victor Bodnarchuka, Alexander Ioffe

c and Alexander Belushkin

a

a Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia b Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Bucharest-Magurele MG-6 077125,

Romania, erhan@tandem.nipne.ro c Jülich Centre for Neutron Science-Outstation Garching, Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747

Garching, Germany Making use of polarized neutrons at neutron spectrometers became rapidly a well-known technique at neutron sources. Neutron spin handling devices that employ time-dependent magnetic fields are very frequently used in different polarized neutron instruments. Considering the recent developments of the VITESS software package and the polarization suite provided by it [1], we will present the results of the Monte Carlo simulations of a neutron spin echo spectrometer and its components with [2,3] and without pulsed (i.e. time-gradient) magnetic fields. The simulations will outline the performance of the neutron spin-echo spectrometers and the performance of the SESANS option of a NSE spectrometer with time-gradient magnetic fields. References [1] S. Manoshin, A. Belushkin, A. Ioffe, Physica B 406 (2011) 2337-2341. VITESS polarized neutron suite: allows for the simulation of performance of any existing polarized neutron scattering instrument. [2] A. Ioffe, V. Bodnarchuk, K. Bussmann, R. Müller, Physica B 397 (2007) 108-111. Larmor labeling by time-gradient

magnetic fields. [3] A. Ioffe, V. Bodnarchuk, K. Bussmann, R. Müller, R. Georgii, NIMA 586 (2008) 36-40. A new neutron spin–echo spectrometer with time-gradient magnetic fields: First experimental test.

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B20

Performance of IN15 polarizing and analysing supermirror devices.

T. Bigault1, D. Jullien

1, B. Farago

1, P. Falus

1

Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble, France, bigault@ill.fr On the spin-echo instrument IN15 at the ILL [1], supermirror devices have been installed or upgraded during the last 6 years in order to polarize and analyse efficiently neutrons with wavelengths ranging from 0.5 to 2.5 nm. In this presentation, the main features of the two polarizing devices (one reflecting mirror and one V-shaped transmission device) and of the analyser will be presented. These devices use in-house coated Fe/Si and Co/Ti supermirrors, with m-values ranging from 2.5 to 3.6. Thanks to opaque polarized 3He spin filter cells, it is possible to measure the polarizers and analyser polarisation performances independently, directly on the instrument in a realistic configuration. The results from such a measurement will be presented. References [1] P. Schleger, G. Ehlers, A. Kollmar et al.,The sub-neV resolution NSE spectrometer IN15 at the Institute Laue Langevin, Physica B, 266, 49-55 (1999).

B21

Wide-aperture fan neutron supermirror analyzer of polarization for Magnetism Reflectometer

Syromyatnikov V.G.1

, Ulyanov V.A.1

, Lauter V.2

, Bulkin A.P.1

, Pusenkov V.M.1

Petersburg Nuclear Physics Institute, 188300, Gatchina, St.Petersburg, Russia,

svg@pnpi.spb.ru 1 - Petersburg Nuclear Physics Institute, 188300, Gatchina, St.Petersburg, Russia,

2 – SNS, Oak Ridge National Laboratory P.O. Box 2008 Oak Ridge, TN 37831, USA During the last years in PNPI it has been created two highly effective supermirror analyzers of polarisation of fan type for neutron reflectometers REMUR (JINR, Russia) [1] and NeRo (GKSS, Germany) [2]. A new improved wide aperture analyzer of polarization of fan type on the basis of polarizing supermirrors SwissNeutronics is created in PNPI for neutron Magnetism Reflectometer (SNS ORNL, USA). The analyzer is installed in front of the two coordinate position-

sensitive detector with sensitive area 260 × 260 mm2

. The neutrons with wavelengths from 2 to 12 Å are used in

reflectometer. The analyzer consists of 157 channels and its entrance cross-section is 120× 240 mm2

. In the paper the results of calculations and tests of the analyzer are presented. References [1] Yu.V. Nikitenko, V.A. Ulyanov, V.M. Pusenkov, S.V. Kozhevnikov, K.N. Jernenkov, N.K. Pleshanov, B.G. Peskov, A.V. Petrenko, V.V. Proglyado, V.G. Syromyatnikov, A.F. Schebetov, Nuclear Instruments and Methods A 564 (2006) 395. A fan analyzer of neutron beam polarization on the spectrometer REMUR at the pulsed reactor IBR-2. [2] V.G.Syromyatnikov, A.F.Schebetov, D.Lott, A.P.Bulkin, N.K.Pleshanov, V.M.Pusenkov, Nuclear Instruments and Methods A 634 (2011) s126. PNPI wide-aperture fan neutron supermirror analyzer of polarization.

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B22

Neutron-optical system of the channel GEK- 4-4’ of reactor PIK

Syromyatnikov V.G., Schebetov A.F., Pusenkov V.M., Pleshanov N.K., Serebrov A.P., Bulkin A.P.

Petersburg Nuclear Physics Institute, 188300, Gatchina, St.Petersburg, Russia, svg@pnpi.spb.ru

Petersburg Nuclear Physics Institute, 188300, Gatchina, St.Petersburg, Russia In the next some years in PNPI the new research high-flux reactor PIK will be started. The horizontal channel of the GEK4-4’ of reactor PIK will be equipped with a liquid hydrogen source of cold and ultracold neutrons. Use of this channel for carrying out basic researches on physics of weak interactions with the polarized neutrons is planned. For this channel in PNPI, on the basis of the experience [1], the highly effective wide-aperture polarized neutron-optical system was developed for both parts of the channel. In paper results of calculations of neutron-optical characteristics of this system are presented. Comparison of this system with the best foreign analogs is carried out. References [1] A. Schebetov, A. Serebrov, V. Pusenkov, M. Lasakov, P. Böni, M. Lüthy, and J. Sromicky, Nuclear Instruments and Methods A 497 (2003) 479. New Facility for Fundamental Research in Nuclear Physics with Polarized Cold Neutrons at PSI.

B23

Design study of neutron spin flippers for a new neutron reflectometer at J-PARC

H. Hayashida1, M. Takeda

2, D. Yamazaki

1, R. Maruyama

1, K. Soyama

1, M. Kubota

2, T. Mizusawa

3, Y. Sakaguchi

3 and

N. Yoshida3

1J-PARC Center, JAEA, Tokai, Ibaraki 319-1195, Japan, e-mail:hayashida.hirotoshi@jaea.go.jp 2Neutron Materials Research Center, Quantum Beam Science Directorate, JAEA, Tokai, Ibaraki 319-1195, Japan

3Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan A new neutron reflectometer SHARAKU with vertical sample-plane geometry was installed to the beam line 17 at Materials and Life science experiment Facility (MLF) at J-PARC. Experiments with polarized neutron can be performed for the specular and off-specular mode. Magnetism in thin magnetic film is one of the main targets on SHARAKU and neutron spin flippers were installed. Since a high total polarization of neutron spin more than 0.95 (Ptotal≧0.95) is required for the magnetism study, polarization of more than 0.985 is required for each spin flippers with wide wavelength band of from 0.24 nm to 0.75 nm. A two-coil spin flipper is installed to the upstream of the sample position. At the downstream of the sample position, another two-coil spin flipper and mezei-type spin flipper are selectively used for the specular and off-specular measurements, respectively. Both of the two-coil spin flippers cover a beam size of 50 mm in vertical and 5 mm in horizontal. The mezei-type spin flipper covers more wide area of 50 mm in vertical and 100 mm in horizontal in order to control a neutron spin reflected by off-specular. Design studies of these spin flippers with magnetic field simulation and neutron spin analysis along the simulated field was performed. As a result, the two-coil flipper which covers beam area of the above with P > 0.985 and the mezei-type flipper which covers beam area of the above with P > 0.987 were designed.

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B24

Design study of magnetic environments for XYZ polarization analysis using 3He for the new thermal time of flight spectrometer TOPAS

Zahir SALHI, Earl BABCOCK, Alexander IOFFE

Jülich Centre for Neutron Science at the FRM II, Garching, Germany e-mail address: z.salhi@fz-juelich.de

Abstract: We present a finite element calculation of the magnetic field (MagNet software) taken with the newly proposed PASTIS Coil, which uses a wide-angle banana shaped 3He Neuton Spin Filter cell (NSF) to cover a large range of scattering angle. The goal of this insert is to enable XYZ polarization analysis to be installed on the future thermal time-of flight spectrometer TOPAS. Polarization analysis, PA, of polarized neutrons is a powerful tool for separation of nuclear spin-incoherent background, analysis of complex magnetic structures and the study of magnetic excitations. Several wide angle spectrometers with polarization analysis exist or are under construction in which PA is used. The PA can be performed in a variety of ways depending on the instrument’s parameters, but with performance limited by the analyzer height and integration over the height of the detectors. Installation of a new longer, height-position sensitive detector bank

gives a unique opportunity to prototype and test a polarized 3He XYZ analysis system which could utilize the full height

and position resolution of these new detectors. We present an initial design study with finite element magnetic field (FEM) calculations of possible XYZ field configurations suitable for polarized 3He and adapted to the TOPAS instrument geometry

B25

Solving and Refining Magnetic Structures by Combined Polarimetry and Integrated Intensity data

Juan Rodriguez-Carvajal, Oksana Zaharko

Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France. E-mail: jrc@ill.eu Paul Scherrer Institute, SINQ, Villigen, Switzerland. E-mail: oksana.zaharko@psi.ch

In the present communication we present a new program, MagOptim, using simulated annealing followed by local optimization, to solve and refine magnetic structures using, simultaneously, data coming from polarimetry measurements with CryoPAD, or MuPad, and conventional integrated intensities. Whatever kind of magnetic structure can be treated using the formalism of propagation vectors. Full account of domains is taken into account for treating the data. In the communication the Blume-Maleyev formulae [1, 2] adapted to crystallographic conventions are discussed in detail showing the way the domains are treated in the program. The program is still in a test stage and improvements are currently being performed. The program is based in CrysFML [3] and has been developed taking as template a previous program for solving crystal structures (see directory Structures_GlobalOptimization in the repository [4]). The program is freely available, including the source code, from the ILL forge [4]. [1] M. Blume, Phys. Rev. 130, 1670-1676 (1963). [2] Maleyev, S.V., Bar’yachtar, V.G., et Suris, P.A., Sov. Phys. Solid State 4, 3461 (1963). [3] J, Rodriguez-Carvajal and J Gonzalez-Platas, Compcomm Newsletter 1, 50-58 (2003). “Crystallographic Fortran Modules Library (CrysFML): A simple toolbox for crystallographic computing programs”,Computing Commission of the International Union of Crystallography. [4] The library CrysFML and related programs, in particular the program MagOptim, are accessible at: https://forge.ill.eu/projects/crysfml/repository

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B26

Development of RF-flippers for large angle NRSE. Klimko Sergey, Longeville Stephane, Malikova Natalie

Laboratoire Léon Brillouin, CEA Saclay, France (sergey.klimko@cea.fr)

The widening of the detection area of the NRSE spectrometer MUSES requires using large solid angle (LSA) resonance spin flippers. The aim of the Multi-MUSES project [1] is to design and construct LSA flippers with a “curved” geometry. Each flipper consists of a combination of vertical coil producing a static magnetic field of the order of a few hundred Gauss, and radiofrequency coil used for the generation of horizontal oscillating field in the frequency range between 50 kHz and 1 MHz. The design of the flipper which corresponds to the shorter radius of curvature is the most difficult task to realize, in terms of obtaining curved coils with required field values and acceptable field homogeneity. This work presents the calculation and optimization of a curved radiofrequency coil and an approach to the design of static coils for bootstrap flipper combination. We show that curved radiofrequency coils should be equipped with additional compensation coils to approach the homogeneity ±1% over the 30˚ of scattering angle. To homogenize static magnetic field it is preferable to use mu-metal yoke for each curved coil rather than to interconnect bootstrap coils with mu-metal plates at the top and bottom of the coils. References [1] J.-M. Zanotti, S. Combet, S. Klimko, S. Longeville and F. Coneggo, Neutron News 22 (2011) 24. Present and future of the quasi-elastic neutron spectroscopy at LLB. More than simply samples: devices.

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Participants list

Earl BABCOCK e.babcock@fz-juelich.de Jülich Centre for Neutron Science, Munich Gerald BADUREK badurek@ati.ac.at Vienna University of Technology / Atominstitut Patrick BARONI patrick.baroni@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Thierry BIGAULT bigault@ill.fr Institut Laue Langevin, Grenoble Stephen BOAG stephen.boag@stfc.ac.uk ISIS, STFC, Oxford François BOUE francois.boue@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Andrew BOOTHROYD a.boothroyd@physics.ox.ac.uk University of Oxford Frederic BOURDAROT frederic.bourdarot@cea.fr CEA Grenoble Markus BRADEN braden@ph2.uni-koeln.de Universität zu Köln Steve BRAMWELL s.t.bramwell@ucl.ac.uk London Centre for Nanotechnology and Dpt of Physics and Astronomy Georg BRANDL georg.brandl@frm2.tum.de FRM II, Münich Gregory CHABOUSSANT gregory.chaboussant@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Mun CHAN mchan053@gmail.com University of Minnesota Lieh-Jeng CHANG ljchang@mail.ncku.edu.tw National Cheng Kung University, Taiwan Laurent CHAPON chapon@ill.fr Institut Laue Langevin, Grenoble Wangchun CHEN wcchen@nist.gov NIST and University of Maryland Pierre COURTOIS courtois@ill.fr Institut Laue Langevin, Grenoble Françoise DAMAY francoise.damay@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Pascale DEEN pascale.deen@esss.se European Synchrotron Radiation Facility, Grenoble Sylvain DESERT sylvain.desert@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Maxime DEUTSCH maxime.deutsch@crm2.uhp-nancy.fr Université de Lorraine, Nancy Sabrina DISCH sabrina.disch@gmx.de JCNS and ILL Joe DONALDSON joe.donaldson@stfc.ac.uk ISIS, STFC, Oxford Zakaria ELAOUD zakaria_elaoud@yahoo.com Faculté des Sciences de Sfax, Tunisie Raul Victor ERHAN raul.erhan@gmail.com Department of Nuclear Physics, Bucharest Benjamin FRANDSEN baf2128@columbia.edu Columbia University in the City of New York Alexander FRANK frank@nf.jinr.ru Frank Laboratory of Neutron Physics, Moscow Thomas GENTILE thomas.gentile@nist.gov NIST Robert GEORGII robert.georgii@frm2.tum.de FRM II, Münich Béatrice GILLON beatrice.gillon@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Christoph GÖSSELSBERGER goesselsberger@ati.ac.at Vienna University of Technology, Atominstitut Martin GREVEN greven@physics.umn.edu University of Minnesota Sergey GRIGORIEV grigor@pnpi.spb.ru Petersburg Nuclear Physics Institute, Gatchina

79

Natalia GRIGORYEVA natali@lns.pnpi.spb.ru Saint-Petersburg State University Felix GROITL felix.groitl@helmholtz-berlin.de Helmholtz-Zentrum Berlin für Materialien und Energie Alexander GRUENWALD gruenwald@ph2.uni-koeln.de University of Cologne Arsen GUKASOV arsen.goukassov@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Klaus HABICHT habicht@helmholtz-berlin.de Helmholtz-Zentrum Berlin für Materialien und Energie Wolfgang HAEUSSLER wolfgang.haeussler@frm2.tum.de FRM II, Münich Patrick HAUTLE patrick.hautle@psi.ch Paul Scherrer Institut, Switzerland Hirotoshi HAYASHIDA hayashida.hirotoshi@jaea.go.jp Japan Atomic Energy Agency, Tokai Bill HERSMAN hersman@unh.edu University of New Hampshire et Xemed LLC Trevor HICKS trevor.hicks@monash.edu.au Monash University, Australia Masahiro HINO hino@rri.kyoto-u.ac.jp Research Reactor Institute, Kyoto University Sonja HOLM sonja@fys.ku.dk Niels Bohr Institutet, Nano-Science Center, Copenhagen Takashi INO takashi.ino@kek.jp KEK, Japan Alexander IOFFE a.ioffe@fz-juelich.de Jülich Centre for Neutron Science, Münich Henrik JACOBSEN henrik.jacobsen.fys@gmail.com Niels Bohr Institute, Copenhagen Erwin JERICHA jericha@ati.ac.at Vienna University of Technology, Atominstitut Thomas KELLER t.keller@fkf.mpg.de MPI for Solid State Research, Stuttgart and FRM II Nikolay KARDJILOV kardjilov@helmholtz-berlin.de Helmholtz Centre Berlin Yury KHAYDUKOV Yury.Khaydukov@frm2.tum.de FRM II, Münich Jonas KINDERVATER jonas.kindervater@frm2.tum.de Physik Department E21, Technische Universität München Hiroshi KIRA h_kira@cross.or.jp Comprehensive Research Organization for Science and Society, Japan Christine KLAUSER klauser@ill.fr Institut Laue-Langevin, Grenoble Sergey KLIMKO sergey.klimko@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Sergey KOZHEVNIKOV kozhevn@nf.jinr.ru Frank Laboratory of Neutron Physics, JINR, Dubna Vladimir KOZHEVNIKOV vladimir@itf.fys.kuleuven.be Tulsa Community College, USA Wolfgang KREUZPAINTNER Wolfgang.Kreuzpaintner@frm2.tum.de Technische Universität München, Physik-Department E21 Thomas KRIST krist@helmholtz-berlin.de Helmholtz-Zentrum Berlin Kathryn KRYCKA kathryn.krycka@nist.gov NIST Center for Neutron Research Daniel LAMAGO daniel.lamago@cea.fr Laboratoire Léon Brillouin, Paris Valeria LAUTER lauterv@ornl.gov Oak Ridge National Laboratory Wai Tung LEE wtl@ansto.gov.au Australian Nuclear Science and Technology Organisation Eddy LELIEVRE-BERNA lelievre@ill.eu Institut Laue Langevin, Grenoble Lian LIU lllinger1989@gmail.com Columbia University in the city of New York Emilio LORENZO emilio.lorenzo@grenoble.cnrs.fr Institut Néel, CNRS Grenoble Dieter LOTT dieter.lott@hzg.de Helmholtz-Zentrum Geesthacht Chin Shan LUE CHIN SHAN cslue@mail.ncku.edu.tw National Cheng Kung University, Taiwan Dominique LUNEAU luneau@univ-lyon1.fr Université Claude Bernard Lyon 1

80

Garry MCINTYRE garry.mcintyre@ansto.gov.au Australian Nuclear Science and Technology Organisation Nicolas MARTIN nicolas.martin@frm2.tum.de FRM II, Münich Ryuji MARUYAMA ryuji.maruyama@j-parc.jp J-PARC Center, Japan Atomic Energy Agency Stefan MATTAUCH s.mattauch@fz-juelich.de JCNS, Münich Vasily MATVEEV matveev@lns.pnpi.spb.ru Petersburg Nuclear Physics Institute, Gatchina Lucile MANGIN-THRO lucile.mangin-thro@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Alain MENELLE Alain.Menelle@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Andreas MICHELS andreas.michels@uni.lu Laboratory for the Physics of Advanced Materials, Luxembourg Evgeny MOSKVIN emoskvin@gmail.com Petersburg Nuclear Physics Institute, Gatchina Balint NAFRADI nafradi@yahoo.com Laboratory of Nanostructures and Novel Electronic Materials, EPFL Michihiro NAGAO mnagao@nist.gov NIST and Indiana University Kirill NEMKOVSKI k.nemkovskiy@fz-juelich.de Jülich Centre for Neutron Science Jennifer NIEDZIELA jen.niedziela@gmail.com Joint Institute for Neutron Sciences, Oak Ridge Yuri NIKITENKO nikiten@nf.jinr.ru Frank Laboratory of Neutron Physics, Dubna Yohei NODA noda.yohei@jaea.go.jp Japan Atomic Energy Agency Laurence NOIREZ Laurence.Noirez@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Tatsuro ODA t_oda@nucleng.kyoto-u.ac.jp Department of Nuclear Engineering, Kyoto University Kenji OHOYAMA ohoyama@imr.tohoku.ac.jp Institute for Materials Research, Tohoku University Takayuki OKU oku.takayuki@jaea.go.jp J-Parc Center, JAEA Shigeki ONODA s.onoda@riken.jp Condensed Matter Theory Laboratory, RIKEN , Japan Frederic OTT Frederic.Ott@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Fernando PALACIO palacio@unizar.es Instituto de Cienca de Materiales de Aragon, SPAIN Catherine PAPPAS c.pappas@tudelft.nl TU Delft Steven PARNELL srPARNELL@googlemail.com CEEM, USA Alexander PETUKHOV petukhov@ill.fr Institute Laue-Langevin, Grenoble Sylvain PETIT Sylvain.Petit@cea.fr Laboratoire Léon Brillouin, CEA/CNRS, Paris Florian PIEGSA florian.piegsa@phys.ethz.ch ETH Zürich Jeroen PLOMP j.plomp@tudelft.nl Delft University of Technology Amy POOLE amy.poole@psi.ch PSI, Switzerland Nadya POTAPOVA potapova@lns.pnpi.spb.ru Petersburg Nuclear Physics Institute Louis-Pierre REGNAULT regnault@ill.fr CEA Grenoble Julia REPPER Julia.Repper@psi.ch Paul Scherrer Institut, Switzerland Juan RODRIGUEZ-CARVAJAL jrc@ill.fr Institut Laue-Langevin Vladimir RUNOV runov@pnpi.spb.ru Petersburg Nuclear Physics Institute Zahir SALHI z.salhi@fz-juelich.de Jülich Centre for Neutron Science Philipp SCHMAKAT philipp.schmakat@frm2.tum.de Technische Universität München, FRM II Werner SCHWEIKA w.schweika@fz-juelich.de JCNS, Forschungszentrum Jülich

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Takenao SHINOHARA takenao.shinohara@j-parc.jp J-PARC Center, Japan Atomic Energy Agency virginie SIMONET virginie.simonet@grenoble.cnrs.fr Institut Néel, Grenoble Markos SKOULATOS markos.skoulatos@psi.ch Laboratory for Neutron Scattering, PSI, Switzerland Markus STROBL markus.strobl@esss.se European Spallation Source, Lund Amir SYED MOHD AMIR smamir.alig@gmail.com UGC-DAE Consortium for Scientific Research, Indore, India Vladislav SYROMYATNIKOV svg@pnpi.spb.ru Petersburg Nuclear Physics Institute Masayasu TAKEDA takeda.masayasu@jaea.go.jp Japan Atomic Energy Agency Kaoru TAKETANI kaoru.taketani@kek.jp KEK, Japan Vladislav TARNAVICH tarnavich@lns.pnpi.spb.ru Petersburg Nuclear Physics Institute Wolfgang TREIMER treimer@helmholtz-berlin.de Helmholtz Centre Berlin for Materials and Energy Oleg UDALOV udalov@ipmras.ru Institute for Physics of Microstructures, Nizhny Novgorod, Russia Victor UKLEEV ukleev@lns.pnpi.spb.ru Petersburg Nuclear Physics Institute Eugene VELICHKO evgen@pnpi.spb.ru Petersburg Nuclear Physics Institute Vladimir VORONIN vvv@pnpi.spb.ru Petersburg Nuclear Physics Institute Meng WANG wangm@iphy.ac.cn Institute of Physics, Chinese Academy of Sciences Shannon WATSON shannon.watson@nist.gov NIST Center for Neutron Research Albrecht WIEDENMANN wiedenmann@ill.fr ILL Grenoble Xin XIN TONG tongx@ornl.gov OAK RIDGE NATIONAL LABORATORY Tetsuya YOKOO tetsuya.yokoo@kek.jp High Energy Accelerator Research Organization KEK, Japan Oksana ZAHARKO Oksana.Zaharko@psi.ch Laboratory for Neutron Scattering, PSI, Switzerland Jinkui (J.K.) ZHAO zhaoj@ornl.gov Oak Ridge National Lab. Kirill ZHERNENKOV v-zherne@ill.fr Ruhr University Bochum Fatih ZIGHEM zighem@gmail.com Université Paris XIII