Past and Future Insights from Neutron Scattering Collin Broholm*

Johns Hopkins University and NIST Center for Neutron Research

Virtues and Limitations of Neutron Scattering

New Sources and Instrumentation

Capabilities of New Instrumentation

Conclusionsik

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* supported by NSF DMR-0074571

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Zachary Fisk and Neutron Scattering

More than 70 papers on neutron scattering: Heavy Fermion Systems Kondo Insulators Valence Fluctuating systems High TC superconductors

Neutrons used to probe Magnetic order and Fluctuations Structure and sample quality Thermal Expansion Phonons

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Spin Fluctuations in U2Zn17

Broholm et al. PRL (1987)

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Structure of YbInCu4

d-spacing (A)

Inte

nsity

(103 c

ount

s/s

)

Lawrence et al PRB (1996)

•Contrast between elements with similar Z•Sensitivity to light atoms in heavy matrix

a probe of sample quality

Flux-grown crystal

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Magnetic Structure of CeRhIn5

Bao et al PRB (2000)

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Probing Spin Density Distribution

UPt3

U 5f, 6d, and -7f spin polarizationPt polarized as well

UBe13

Only U polarized

Neumann, Brown, et al. Physica B (1991)

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Electronic Interactions in La2CuO4

Coldea et al PRL (2001)

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What makes it hard

150 MeV thermal energy per neutron (fission) a factor Z2 less than X-ray scattering Limitations of current instrumentation

dynamics in samples < 1 mm3

dynamics in nano-structured solids Lateral surface structure complex materials with weak signals Signals from impurities at low concentration Spatial and temporal resolution Pressure above 25 GPa

2cr

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Expanding Applicability of a Powerful Probe

Increase source brightness Increase spectral brightness by cooling neutrons Increase temporal brightness in pulsed neutron source

Improve beam delivery system Match solid angle to wave vector resolution requirements Match bandwidth to energy resolution requirements

Increase solid angle of detection system Position sensitive detectors Crystal analyzer arrays

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New Instrumentation and Sources

NIST cold source and instrument upgrade 2002-4 HFIR cold source and instrument upgrade 2002 LANSCE source and instrument upgrade 2002 US Spallation Neutron Source 2006 German high flux research reactor 2004 Australian high flux research reactor 2005 Japanese Spallation Neutron Source 2006 European Spallation Neutron Source ? Chinese Advanced Research reactor ?

Instrument Begin E (meV) Condensed Matter Science Enabled

FANS 1999 1-3 Phonon Density of States

Spin Echo 2000 10-5 Flux lattice dynamicsDynamic Correlations in Glasses

Back Scattering 1999 10-3 Critical PhenomenaQuantum Tunelling

Disc Chopper 2001 10-2-1 Quantum Critical phenomenaPhonon density of states

MACS 2004 10-2-1 Structure of fluctuating systemsImpurity dynamicsInelastic Scattering from small samples

New Instruments for CMP at NIST

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Intensity from Focusing

1428 cm2 PG(002)

MC Simulation Qiu and Broholm (2001)

MACS monochromator

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Upgraded Neutron Scattering Facilities at HFIR, ORNL

Upgraded Neutron Scattering Facilities at LANSCEInstrument Begin Specification Condensed Matter

Science Enabled HIPPO Powder Diffractometer

2002 0.35%<Q/Q<5% V1 mm3

Structure and Texture of disordered materials

SMARTS eng. Diffractometer

2001 1 mm3<V<1 m3 Residual Strain in Engineered Structures

Protein Crystallography

2001 TOF sorted Laue diffraction

H-positions in Protein Structure

PHAROS Spectrometer

2002 E/E=0.5% 1 meV<E<1 eV

Room T Lattice and Spin Dynamics

ASTERIX reflectometer

2001 Polarized beam Structure of solid and magnetic interfaces

eV Spectrometer

2004 Rep-rate multiplication

Low T Lattice, Spin, and Liquid Dynamics

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Fisk Fest 8/15/01May 2001 Aug 7 2001

Instrument Begin Specification Condensed Matter Science Enabled

Silicon Backscattering

2006 eV<E<10eV 0.1Å-1<Q<3.8Å-1

Diffusion, tunneling, and solvent dynamics

Vertical Reflectometer

2006 0<Q<7Å-1 R>10-10

Structure of solid and magnetic interfaces

Horizontal Reflectometer

2006 0<Q<0.5 Å-1

R>10-10 Structure of Liquid interfaces

Extended Q SANS

2006 0.004Å-1<Q<12Å-1 Nano-scale solid and solvent structure

Powder Diffraction

2006 0.1%<Q/Q<1.6% V<0.1 cm3

High Resolution Structure

meV-eV Spectrometer

2006 1.5%<E/E<5% 1 meV<E<1 eV

Room T Lattice and Spin Dynamics

eV-meV Spectrometer

2006 3%<E/E<10% 0 meV<E<20 meV

Low T Lattice, Spin, and Liquid Dynamics

Instruments for CMP at SNS

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Neutrons in the 21 centuryChemical and magnetic structure at the interfaces of nano-

scale artificially structured systemsExcitations in materials patterned on the nano-scaleProtein structure (including D-positions) and dynamicsComplete 4 D Q-E mapping of dynamic correlation

function for spin and lattice in large single crystals 0<E<100 meV

Systematic access to order parameters of weak or complex broken symmetry phases

Inelastic neutron scattering as a super-susceptometer for screening new materials

Parametric and complete information about structure of matter under extreme conditions

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Conclusions

Neutrons are great but we don’t have enough yet

New sources and instrumentation should produce a renaissance for the technique

New facilities must be easily accessible to non-neutron-experts to broaden the science program