Absence of an induced magnetic moment in Pt on … · Absence of an Induced Magnetic Moment in Pt...
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Absence of an Induced Magnetic Moment in Pt on Y 3 Fe 5 O 12 Stephan Geprägs 1 , Matthias Opel 1 , Sibylle Meyer 1 , Fabrice Wilhelm 2 , Katharina Ollefs 2 , Andrei Rogalev 2 , Sebastian T.B. Goennenwein 1 , Rudolf Gross 1,3 1 Walther - Meißner - Institut (WMI), Bayerische Akademie der Wissenschaften , 85748 Garching , GERMANY 2 European Synchrotron Radiation Facility (ESRF), 38043 Grenoble Cedex 9, FRANCE 3 Physik - Department, Technische Universität München, 85748 Garching, Germany www.wmi.badw.de MA 55.9 – DPG Frühjahrstagung (Dresden, 2014) www.wmi.badw.de Yttrium Iron Garnet (YIG, Y 3 Fe 5 O 12 ) and Pt Spin Currents X-Ray Absorption Near Edge Spectra (XANES) Summary This work was supported by the ESRF via HE-3784 and the DFG via priority program SPP 1538. High -quality epitaxial Y 3 Fe 5 O 12 (YIG) thin films via pulsed laser deposition on Y 3 Al 5 O 12 (YAG) substrates In -situ e-beam evaporation of thin Pt layers (1.6, 3, 7, 10 nm) XANES at Pt L 2,3 edges compatible with metallic Pt on Y 3 Fe 5 O 12 No indication for oxidation of Pt → high interface quality Element -specific magnetization in four Pt|Y 3 Fe 5 O 12 samples Finite XMCD for Pt|Fe (FMM), no XMCD for Pt|Y 3 Fe 5 O 12 (FMI) No indication for magnetic proximity effect in Pt on Y 3 Fe 5 O 12 Supports spin -Hall interpretation of MR in Pt (SMR model) Element-Specific Investigation Laser-MBE of Y 3 Fe 5 O 12 Thin Films [1] H. Nakayama et al., Phys. Rev. Lett. 110 , 206601 (2013). [2] M. Althammer et al., Phys. Rev. B 87 , 224401 (2013). [3] S. Meyer et al., submitted to Appl. Phys. Lett. (2014), arXiv:1401.7787 [4] Y.M. Lu et al., Phys. Rev. Lett. 110 , 147207 (2013). [5] Y.-T. Chen et al., Phys. Rev. B 87 , 144411 (2013). [6] S. Geprägs et al., Appl. Phys. Lett. 101 , 262407 (2012). [7] S. Geprägs et al., arXiv:1307.4869 (2013). Comparison with MPMR model (Lu et al.) Magnetic Proximity MR vs. Spin-Hall MR X-Ray Magnetic Circular Dichroism (XMCD) resonant excitation theory: Tserkovnyak, PRL 88 , 117601 (2002) expt.: Mosendz, PRL 104 , 046601 (2010) scaling: Czeschka, PRL 107 , 046601 (2011) FMM: Uchida, Nature 455 , 778 (2008) FMI: Uchida, Nature Mater. 9 , 894 (2010) DMS: Jaworski, Nature Mater. 9 , 898 (2010) local SSE: Weiler, PRL 108 , 106602 (2012) thermal excitation Transfer of Angular Momentum, No Transfer of Electrical Charge spin current normal metal NM ferromagnet FM magnons spin current detection → via inverse spin-Hall effect (iSHE) in normal metal (NM) problem → conductivity of the ferromagnet (FM) solution → use ferromagnetic insulators (FMI) NECESSARY: Clean Interfaces Element-Specific Determination of Induced Magnetic Moments Finite Magnetoresistance (MR) in non-magnetic Pt m agnetic p roximity m agneto- r esistance (MPMR) idea: induced magnetic moments in Pt on Y 3 Fe 5 O 12 Huang et al., PRL 109 , 107204 (2012) Lu et al., PRL 110 , 147207 (2013) Nakayama et al., PRL 110 , 206601 (2013) Althammer et al., PRB 87 , 224401 (2013) Meyer et al., APL (2014), arXiv:1401.7787 Experiments (compatible): s pin-Hall m agnetor esistance (SMR) theory/model: absorption of spin current by ferromagnetic insulator (FMI) Chen et al., PRB 87 , 144411 (2013) experimentally established for Pt on ferromagnetic metals (FMM) Parra and Medina, PRB 22 , 5460 (1980) Wilhelm et al., PRL 85 , 413 (2000) Wilhelm et al., PRL 87 , 207202 (2001) Wende, Rep. Prog. Phys. 67 , 2105 (2004) Wilhelm et al., PRB 69 , 220404 (2004) magnetic proximity effects ? Y 3 Fe 5 O 12 Pt Pt/Y 3 Fe 5 O 12 Pt/Au/Y 3 Fe 5 O 12 Pt/Cu/Y 3 Fe 5 O 12 Pt/Fe 3 O 4 Pt/NiFe 2 O 4 FMI: Y 3 Fe 5 O 12 (y ttrium i ron g arnet, YIG) NM: Pt (large spin-Hall angle) Y 3 Fe 5 O 12 (YIG) ferrimagnetic due to Fe 3+ ions high Curie temperature T C = 560 K electrically insulating Nakayama et al., PRL 110 , 206601 (2013) -40 -20 0 20 40 408.7 408.8 408.9 long (nm) Althammer et al., PRB 87 , 224401 (2013) -20 -10 0 10 20 -150 -100 -50 0 50 100 150 M (kA/m) 0 H (mT) Experimental observations magnetic hysteresis in ferrimagnetic Y 3 Fe 5 O 12 magnetoresistance effect in non -magnetic Pt magnetic proximity effect? European Synchrotron Radiation Facility (ESRF) Beamline ID12 Pt Fe L 2 edge: 2p 1/2 → 5d 13273 eV L 3 edge: 2p 3/2 → 5d 11564 eV K edge: 1s → 3d 7112 eV X-ray Absorption Near Edge Spectra XANES element-specific X-ray absorption X-ray Magnetic Circular Dichroism XMCD = XANES (H+,σ+) – XANES (H-,σ+) = XANES (H+,σ+) – XANES (H+,σ-) magnetic field: H (parallel to photons, in-plane) circular polarization: σ XMCD element-specific magnetic X-ray spectroscopy substrate IR heating laser and pyrometer 140 W, 938 nm RHEED screen UV excimer laser 248 nm target carousel zoom optics plasma plume target PLD parameters substrate: Y 3 Al 5 O 12 (111) (YAG) target: Y 3 Fe 5 O 12 (YIG) fluence: 2 J/cm 2 rep. rate: 10 Hz temperature: 500°C atmosphere: 2.5×10 -2 mbar O 2 thickness: ~ 60 nm 20 nm, 10 nm, 7 nm, 3 nm, 1.6 nm Pt by in-situ electron-beam evaporation 60 nm YIG(111) by pulsed laser deposition (PLD) SUB YAG(111) lattice mismatch = 3% Y 3 Fe 5 O 12 (111) FM insulator Pt normal metal Y 3 Al 5 O 12 (111) substrate PLD target PLD plasma plume 10 mm In-situ Thin Film Deposition via PLD (Y 3 Fe 5 O 12 ) and Electron-Beam Evaporation (Pt) -5000 0 5000 -200 -100 0 100 200 no Pt 3 nm Pt 7 nm Pt 10 nm Pt 0 H (mT) M (kA/m) Pt/YIG 300 K -20 0 20 0 H (mT) M (kA/m) 4 NM|FMI samples Pt|Y 3 Fe 5 O 12 on Y 3 Al 5 O 12 NM|FMM reference sample Pt|Fe on Y 3 Al 5 O 12 -100 -50 0 50 100 -1000 -500 0 500 1000 no Pt 10 nm Pt 0 H (mT) Pt/Fe 300 K YIG bulk SQUID Magnetometry SQUID results magnetization of Pt|Y 3 Fe 5 O 12 close to Y 3 Fe 5 O 12 bulk value of 143 kA/m excellent magnetic quality Pt|Fe sample for comparison Appl. Phys. Lett. 101 , 262407 (2012) Pt L 3 normalized whiteline intensity ~1.25 a.u. → compatible with metallic Pt EXAFS wiggles at ~11587 eV and ~13299 eV → characteristic for Pt metal arXiv:1307.4869 (2013) Appl. Phys. Lett. 101 , 262407 (2012) XANES results for Pt metallic Pt layer no indication for oxidation or intermixing with Y 3 Fe 5 O 12 probing depth = Pt thickness 11540 11560 11580 11600 0.00 0.05 0.10 0.15 0.20 0.25 0.035 Pt (3nm)/YIG XANES (a.u.) Photon Energy (eV) Pt (20nm)/YIG 0.185 Absolute XANES Step Intensity Pt L 3 edge thickness: × 6.5 XANES step intensity: × 5.5 11560 11580 11600 13250 13300 13350 0.0 0.5 1.0 1.5 * * L 2 edge norm. XANES (a.u.) 295 K 0.6 T Pt(1.6nm)/YIG Pt L 3 edge 11540 11560 11580 11600 0.0 0.5 1.0 Pt(3nm)/YIG Pt(7nm)/YIG Pt(10nm)/YIG norm. XANES (a.u.) Photon energy (eV) 295 K 60 mT 1.25 1.25 Normalized XANES in Pt|Y 3 Fe 5 O 12 Samples Pt L 3 edge Pt L 2 edge EXAFS wiggle EXAFS wiggle arXiv:1307.4869 (2013) Appl. Phys. Lett. 101 , 262407 (2012) XMCD results XMCD for Pt on Fe BUT: no finite XMCD for Pt on Y 3 Fe 5 O 12 no magnetic proximity effect for Pt on Y 3 Fe 5 O 12 XANES and XMCD in Pt|Fe Reference Sample 11560 11580 11600 13250 13300 13350 0.0 0.5 1.0 1.5 * * L 2 edge norm. XANES (a.u.) 295 K 0.6 T Pt(1.6nm)/YIG Pt L 3 edge -1.0% -0.5% 0.0% 0.5% 1.0% 1.5% 2.0% XMCD 11540 11560 11580 11600 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1.25 Pt(3nm)/YIG Pt(7nm)/YIG Pt(10nm)/YIG norm. intensity (a.u.) Photon energy (eV) XANES XMCD x100 < 0.003 μ B /Pt XANES and XMCD in Pt|Y 3 Fe 5 O 12 Samples from integrated XMCD signal: Pt|Y 3 Fe 5 O 12 : m s < 0.003 μ B /Pt 11540 11560 11580 11600 -1.00 -0.75 -0.50 -0.25 0.00 0.25 0.50 0.75 1.00 1.25 XMCD x100 Pt(10nm)/YIG Pt(10nm)/Fe Photon energy (eV) norm. intensity (a.u.) XANES 0.03 μ B /Pt Pt|Fe: m s = 0.03 μ B /Pt consistent with literature values for Pt|Ni, etc… Phys. Rev. Lett. 110 , 147207 (2013) Lu, Choi, Ortega, Cheng, Cai, Huang, Sun, Chien, PRL 110 , 147207 (2013) XAS/XMCD in only one single Pt|Y 3 Fe 5 O 12 sample 2.07 no detection of EXAFS wiggles Pt L 3 "normalized XAS step height" [3] = 2.07 a.u. → not compatible with metallic Pt from literature Lu et al. report XMCD for Pt on Y 3 Fe 5 O 12 , BUT: XAS/XMCD investigation of only one single sample strong indication for non-metallic Pt MPMR explanation questionable for Pt on Y 3 Fe 5 O 12 Kolobov et al., APL 86 , 121909 (2005) Compound Whiteline Intensity ("XAS step height") PtO 1.6 2.20 a.u. PtO 1.36 1.50 a.u. Pt 1.25 a.u. XRD results epitaxial, oriented growth no secondary phases detectable low mosaic spread FWHM = 0.1° for YIG(444) X-Ray Diffraction (XRD) ω-2θ scan 20° 40° 60° 80° 100° 120° 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 * * I (cps) 2 YIG (888) YAG (888) Y 3 Fe 5 O 12 on Y 3 Al 5 O 12 * 50° 51° 52° 53° 54° 10 1 10 2 10 3 10 4 10 5 YIG (444) YAG (444) Phys. Rev. B 87 , 224401 (2013)
Transcript of Absence of an induced magnetic moment in Pt on … · Absence of an Induced Magnetic Moment in Pt...
Absence of an Induced Magnetic Moment in Pt on Y3Fe5O12
Stephan Geprägs1, Matthias Opel1, Sibylle Meyer1, Fabrice Wilhelm2, Katharina Ollefs2, Andrei Rogalev2,Sebastian T.B. Goennenwein1, Rudolf Gross1,3
1 Walther-Meißner-Institut (WMI), Bayerische Akademie der Wissenschaften, 85748 Garching, GERMANY2 European Synchrotron Radiation Facility (ESRF), 38043 Grenoble Cedex 9, FRANCE3 Physik-Department, Technische Universität München, 85748 Garching, Germany
www.wmi.badw.de
MA 55.9 – DPG Frühjahrstagung (Dresden, 2014)
www.wmi.badw.de
Yttrium Iron Garnet (YIG, Y3Fe5O12) and PtSpin Currents
X-Ray Absorption Near Edge Spectra (XANES)
Summary
This work was supported by the ESRF via HE-3784and the DFG via priority program SPP 1538.
High-quality epitaxial Y3Fe5O12 (YIG) thin films via pulsed laser deposition on Y3Al5O12 (YAG) substrates
In-situ e-beam evaporation of thin Pt layers (1.6, 3, 7, 10 nm)
XANES at Pt L2,3 edges compatible with metallic Pt on Y3Fe5O12
No indication for oxidation of Pt → high interface quality
Element-specific magnetization in four Pt|Y3Fe5O12 samples
Finite XMCD for Pt|Fe (FMM), no XMCD for Pt|Y3Fe5O12 (FMI)
No indication for magnetic proximity effect in Pt on Y3Fe5O12
Supports spin-Hall interpretation of MR in Pt (SMR model)
Element-Specific Investigation
Laser-MBE of Y3Fe5O12 Thin Films
[1] H. Nakayama et al., Phys. Rev. Lett. 110, 206601 (2013).[2] M. Althammer et al., Phys. Rev. B 87, 224401 (2013).[3] S. Meyer et al., submitted to Appl. Phys. Lett. (2014), arXiv:1401.7787[4] Y.M. Lu et al., Phys. Rev. Lett. 110, 147207 (2013).[5] Y.-T. Chen et al., Phys. Rev. B 87, 144411 (2013).[6] S. Geprägs et al., Appl. Phys. Lett. 101, 262407 (2012).[7] S. Geprägs et al., arXiv:1307.4869 (2013).
Comparison with MPMR model (Lu et al.)
Magnetic Proximity MR vs. Spin-Hall MR
X-Ray Magnetic Circular Dichroism (XMCD)
resonant excitation
theory: Tserkovnyak, PRL 88, 117601 (2002)expt.: Mosendz, PRL 104, 046601 (2010)
scaling: Czeschka, PRL 107, 046601 (2011)
FMM: Uchida, Nature 455, 778 (2008)FMI: Uchida, Nature Mater. 9, 894 (2010)
DMS: Jaworski, Nature Mater. 9, 898 (2010)local SSE: Weiler, PRL 108, 106602 (2012)
thermal excitation
Transfer of Angular Momentum, No Transfer of Electrical Charge
spin current
no
rmal
met
alN
M
ferr
om
agn
etFMmagnons
spin current detection→ via inverse spin-Hall effect (iSHE) innormal metal (NM)
problem→ conductivity of the ferromagnet (FM)
solution→ use ferromagnetic insulators (FMI)
NECESSARY:Clean InterfacesElement-Specific Determination of Induced Magnetic Moments
Finite Magnetoresistance (MR) in non-magnetic Pt
magnetic proximity magneto-resistance (MPMR)
idea:induced magnetic momentsin Pt on Y3Fe5O12
Huang et al., PRL 109, 107204 (2012)Lu et al., PRL 110, 147207 (2013)
Nakayama et al., PRL 110, 206601 (2013)Althammer et al., PRB 87, 224401 (2013)Meyer et al., APL (2014), arXiv:1401.7787
Experiments (compatible):
spin-Hall magnetoresistance(SMR)
theory/model:absorption of spin current byferromagnetic insulator (FMI)
Chen et al., PRB 87, 144411 (2013)
experimentally established for Pton ferromagnetic metals (FMM)
Parra and Medina, PRB 22, 5460 (1980)Wilhelm et al., PRL 85, 413 (2000)Wilhelm et al., PRL 87, 207202 (2001)Wende, Rep. Prog. Phys. 67, 2105 (2004)Wilhelm et al., PRB 69, 220404 (2004)
magnetic proximity effects
?Y3Fe5O12
Pt
Pt/Y3Fe5O12
Pt/Au/Y3Fe5O12
Pt/Cu/Y3Fe5O12
Pt/Fe3O4
Pt/NiFe2O4
FMI: Y3Fe5O12
(yttrium iron garnet, YIG)
NM: Pt (large spin-Hall angle)
Y3Fe5O12 (YIG)
ferrimagnetic due to Fe3+ ionshigh Curie temperature TC = 560 Kelectrically insulating
Nakayama et al.,PRL 110, 206601 (2013)
-40 -20 0 20 40
408.7
408.8
408.9
lo
ng (
n
m)
Althammer et al.,PRB 87, 224401 (2013)
-20 -10 0 10 20
-150
-100
-50
0
50
100
150
M (
kA
/m)
0H (mT)
Experimental observations
magnetic hysteresis in ferrimagnetic Y3Fe5O12
magnetoresistance effect in non-magnetic Pt
magnetic proximity effect?
European Synchrotron Radiation Facility(ESRF)
Beamline ID12
Pt
Fe
L2 edge: 2p1/2 → 5d 13273 eVL3 edge: 2p3/2 → 5d 11564 eV
K edge: 1s → 3d 7112 eV
X-ray
Absorption
Near
Edge
Spectra
XANES element-specific X-ray absorption
X-ray
Magnetic
Circular
DichroismXMCD = XANES (H+,σ+) – XANES (H-,σ+)
= XANES (H+,σ+) – XANES (H+,σ-)
magnetic field: H (parallel to photons, in-plane)circular polarization: σ
XMCD element-specific magnetic X-ray spectroscopy
substrate
IR heatinglaser andpyrometer140 W, 938 nm
RHEEDscreen
UV excimerlaser
248 nm
targetcarousel
zoom optics
plasmaplume
target
PLD parameters
substrate: Y3Al5O12(111) (YAG)
target: Y3Fe5O12 (YIG)
fluence: 2 J/cm2
rep. rate: 10 Hz
temperature: 500°C
atmosphere: 2.5×10-2 mbar O2
thickness: ~ 60 nm
20 nm, 10 nm, 7 nm, 3 nm, 1.6 nm Ptby in-situ electron-beam evaporation
60 nm YIG(111)by pulsed laser deposition (PLD)
SUB YAG(111)lattice mismatch = 3%
Y3Fe5O12(111) FM insulator
Pt normal metal
Y3Al5O12(111) substrate
PLD target
PLDplasmaplume
10 mm
In-situ Thin Film Deposition via PLD (Y3Fe5O12) and Electron-Beam Evaporation (Pt)
-5000 0 5000-200
-100
0
100
200
no Pt
3 nm Pt
7 nm Pt
10 nm Pt
0H (mT)
M (
kA
/m)
Pt/YIG
300 K
-20 0 20
0H (mT)
M (
kA
/m)
4 NM|FMI samplesPt|Y3Fe5O12 on Y3Al5O12
NM|FMM reference samplePt|Fe on Y3Al5O12
-100 -50 0 50 100
-1000
-500
0
500
1000 no Pt
10 nm Pt
0H (mT)
Pt/Fe
300 K
YIGbulk
SQUID Magnetometry
SQUID results
magnetization of Pt|Y3Fe5O12
close to Y3Fe5O12 bulk value of 143 kA/m
excellent magnetic quality
Pt|Fe sample for comparison
Appl. Phys. Lett. 101, 262407 (2012)
Pt L3 normalized whiteline intensity ~1.25 a.u.→ compatible with metallic Pt
EXAFS wiggles at ~11587 eV and ~13299 eV→ characteristic for Pt metal
arXiv:1307.4869 (2013)Appl. Phys. Lett. 101, 262407 (2012)
XANES results for Pt
metallic Pt layer
no indication for oxidationor intermixing with Y3Fe5O12
probing depth = Pt thickness
11540 11560 11580 116000.00
0.05
0.10
0.15
0.20
0.25
0.035
Pt (3nm)/YIG
XA
NE
S (
a.u
.)
Photon Energy (eV)
Pt (20nm)/YIG0.185
Absolute XANES Step Intensity
Pt L3 edge
thickness: × 6.5XANES step intensity: × 5.5
11560 11580 11600 13250 13300 13350
0.0
0.5
1.0
1.5
**
L2 edge
norm
. X
AN
ES
(a.u
.)
295 K
0.6 TPt(1.6nm)/YIG
Pt L3 edge
11540 11560 11580 116000.0
0.5
1.0
Pt(3nm)/YIG
Pt(7nm)/YIG
Pt(10nm)/YIGnorm
. X
AN
ES
(a.u
.)
Photon energy (eV)
295 K
60 mT
1.2
51
.25
Normalized XANES in Pt|Y3Fe5O12 Samples
Pt L3 edge Pt L2 edge
EXAFS
wiggle
EXAFS
wiggle
arXiv:1307.4869 (2013)Appl. Phys. Lett. 101, 262407 (2012)
XMCD results
XMCD for Pt on Fe
BUT: no finite XMCD for Pt on Y3Fe5O12
no magnetic proximity effect for Pt on Y3Fe5O12
XANES and XMCD in Pt|Fe Reference Sample
11560 11580 11600 13250 13300 13350
0.0
0.5
1.0
1.5
**
L2 edge
norm
. X
AN
ES
(a.u
.)
295 K
0.6 TPt(1.6nm)/YIG
Pt L3 edge
-1.0%
-0.5%
0.0%
0.5%
1.0%
1.5%
2.0%
XM
CD
11540 11560 11580 11600-0.50
-0.25
0.00
0.25
0.50
0.75
1.00
1.25
Pt(3nm)/YIG
Pt(7nm)/YIG
Pt(10nm)/YIG
norm
. in
tensity (
a.u
.)
Photon energy (eV)
XANES
XMCD
x100
< 0.003 µB/Pt
XANES and XMCD in Pt|Y3Fe5O12 Samples
from integrated XMCD signal:
Pt|Y3Fe5O12: ms < 0.003 µB/Pt
11540 11560 11580 11600-1.00
-0.75
-0.50
-0.25
0.00
0.25
0.50
0.75
1.00
1.25
XMCD x100
Pt(10nm)/YIG
Pt(10nm)/Fe
Photon energy (eV)
norm
. in
tensity (
a.u
.)
XANES
0.03 µB/Pt
Pt|Fe: ms = 0.03 µB/Pt
consistent with literaturevalues for Pt|Ni, etc…
Phys. Rev. Lett. 110, 147207 (2013)
Lu, Choi, Ortega, Cheng, Cai, Huang, Sun, Chien, PRL 110, 147207 (2013)
XAS/XMCD in only one single Pt|Y3Fe5O12 sample
2.0
7
no detection of EXAFS wiggles
Pt L3 "normalized XAS step height" [3] = 2.07 a.u.→ not compatible with metallic Pt
from literature
Lu et al. report XMCD for Pt on Y3Fe5O12, BUT:
XAS/XMCD investigation of only one single sample
strong indication for non-metallic Pt
MPMR explanation questionable for Pt on Y3Fe5O12
Kolobov et al., APL 86, 121909 (2005)
Compound Whiteline Intensity("XAS step height")
PtO1.6 2.20 a.u.
PtO1.36 1.50 a.u.
Pt 1.25 a.u.
XRD results
epitaxial, oriented growth
no secondary phases detectable
low mosaic spreadFWHM = 0.1° for YIG(444)
X-Ray Diffraction (XRD)
ω-2θ scan
20° 40° 60° 80° 100° 120°
101
102
103
104
105
106
107
108
**
I (c
ps)
2
YIG
(888)
YA
G (8
88)
Y3Fe
5O
12
on Y3Al
5O
12
*
50° 51° 52° 53° 54°
101
102
103
104
105
YIG
(444)
YAG
(444)
Phys. Rev. B 87, 224401 (2013)
