Proximity Magnetism and Spin-Hall Anomalous Hall Effectin Pt on Y3Fe5O12 (YIG)Sibylle Meyer1, Richard Schlitz1, Stephan Geprägs1, Matthias Opel1,Fabrice Wilhelm2, Katharina Ollefs2, Andrei Rogalev2, Sebastian T.B. Goennenwein1,3, Rudolf Gross1,3,4
1 Walther-Meißner-Institut (WMI), Bayerische Akademie der Wissenschaften, 85748 Garching, GERMANY2 European Synchrotron Radiation Facility (ESRF), 38043 Grenoble Cedex 9, FRANCE3 Nanosystems Initiative Munich (NIM), 80799 München, GERMANY4 Physik-Department, Technische Universität München (TUM), 85748 Garching, GERMANY
www.wmi.badw.de
International Workshop on Oxide Electronics (Paris, 2015), P47
www.wmi.badw.de
2 4 6-100
-50
0
50
B (
p
m)
µ0H (T)
50
100
150
Pt(3.1nm)|YIGA (
p
m)
Pt(2.0nm)|YIG
Spin Currents
resonantexcitation
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)
thermalexcitation
Transport of Angular Momentum, No Moving Charges
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)
Laser-MBE of Y3Fe5O12 Thin Films
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
Geprägs et al.,Appl. Phys. Lett. 101, 262407 (2012)
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)
Althammer et al.,Phys. Rev. B 87, 224401 (2013)
Pt and Yttrium Iron Garnet (Y3Fe5O12)
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?
Spin-Hall Magnetoresistance (SMR) in Pt on Y3Fe5O12 (YIG)
Spin-Hall Effect in Ptspin separation
Spin Current Jsperpendicular to S and Jq
⇓
Spin Accumulationat the interface to YIG
⇓
Spin Absorption by YIGvia spin-transfer torque (STT)
⇓
Dissipationof spin current Js
⇓
Increase of Electrical Resistivity ρ in Pt⇓
Pt
Y.-T. Chen et al.,Phys. Rev. B 87, 144411 (2013)
YIG
ONLY IFM ⊥ s
Althammer et al.,PRB 87, 224401 (2013)
Nakayama et al.,PRL 110, 206601 (2013)
jC
jS
s
Novel SMR effect:
𝜌SMR = 𝜌0 − 𝜌1𝑚𝑡2
mt = transverse component of M (along s)
Conventional (polycrystalline) AMR effect:
𝜌AMR = 𝜌0 + Δ𝜌 𝑚𝑗2
mj = longitudinal component of M (along jc)
-90° 0° 90° 180° 270°
406.5
406.6
406.7
(
n
m)
300 K
1 T
experimental dataSMR simulation (mt = sin β, ρ ∝ sin2β)AMR simulation (mj = 0)
photo-lithography
rotating magneticfield h
abso
rpti
on
of
spin
cu
rre
nt
refl
ect
ion
of
spin
cu
rre
nt
abso
rpti
on
of
spin
cu
rre
nt
Compound Whiteline Intensity("XAS step height")
PtO1.6 2.20 a.u.
PtO1.36 1.50 a.u.
Pt 1.25 a.u.
Temperature Dependence of the SMR
SMR Amplitude in Pt|Y3Fe5O12
Temperature/thickness dependence
SMR model
0 5 10 15 20
3.0x10-4
6.0x10-4
9.0x10-4
1.2x10-3
3.0x10-4
6.0x10-4
9.0x10-4
1.2x10-3
3.0x10-4
6.0x10-4
9.0x10-4
1.2x10-3
50K
20K
10K
t (nm)
150K
100K
75K
300K
250K
200K
−𝜌1
𝜌0=
2𝛼SH2 𝜆2
𝑡
𝜌𝐺↑↓ tanh𝑡
2𝜆
1 + 2𝜆𝜌𝐺↑↓ coth𝑡𝜆
Y.-T. Chen et al., Phys. Rev. B 87, 144411 (2013)
Pt resistivity: ρPt thickness: tPt spin diffusion
length: λ ≃ 1.5 nm
Pt spin-Hall angle:αSH ≃ 0.08 … 0.11
Spin mixing interfaceconductance:G↑↓ ≃ 4×1014 Ω-1m-2
Meyer et al.,Appl. Phys. Lett. 104, 242411 (2014)
Results from fits
Result
SMR max. forPt Thickness ≈ Spin Diffusion Length
Summary
This work was supported by the ESRF via HE-3784, HC-1500and 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
Finite XMCD for Pt|Fe (FMM), no XMCD for Pt|Y3Fe5O12 (FMI)
No indication for magnetic proximity effect in Pt on Y3Fe5O12
Spin-Hall angle for Pt ≃ 0.08 … 0.11
Spin-Hall anomalous Hall effect with higher order contributions
S. Meyer et al., Appl. Phys. Lett. 104, 242411 (2014).S. Meyer et al., Appl. Phys. Lett. 106, 132402 (2015).M. Althammer et al., Phys. Rev. B 87, 224401 (2013).H. Nakayama et al., Phys. Rev. Lett. 110, 206601 (2013).Y.M. Lu et al., Phys. Rev. Lett. 110, 147207 (2013).Y.-T. Chen et al., Phys. Rev. B 87, 144411 (2013).S. Geprägs et al., arXiv:1307.4869 (2013).S. Geprägs et al., Appl. Phys. Lett. 101, 262407 (2012).
Hall Measurementsin Pt|Y3Fe5O12
Results
Ordinary Hall effect (OHE) changes sign for thin Pt
Anomalous Hall effect (AHE) increases for thin Pt
Higher order contributions to AHEMeyer et al.,Appl. Phys. Lett. 106, 132402 (2015)
Spin-Hall Anomalous Hall Effect (SH-AHE)
𝜌trans = −𝜌2𝑚𝑛
mn = normal componentof M (along n)
𝜌2 =2𝛼SH
2 𝜆2
𝑡
Im𝐺↑↓ tanh2 𝑡2𝜆
𝜌−1 + 2𝜆Re𝐺↑↓ coth𝑡𝜆
2𝜌trans = 𝐴 sin 𝛽 + 𝐵 sin3 𝛽
-2 0 2
-80-40
04080
-2 0 2 -2 0 2
0H (T)
Pt(19.5nm)|YIG
tr
ans(p
m)
= 90°
Pt(6.5nm)|YIG Pt(2.0nm)|YIG
2AHE
0° 180° 360°
-20
-10
0
10
20
tr
an
s (
p
m)
2T
4T
7T
Pt(3.1nm)|YIG
-20
-10
0
10
20
0 5 10 15 20
-10
0
10
20
Pt|YIG
10K
100K
300K
AO
HE(p
m/T
)
Pt thickness t (nm)
SH-AHE theory
ImG = -3x1013
-1m
-2
AA
HE(p
m)
ImG = 1x1013
-1m
-2
Pt L2 edge: 2p1/2 → 5d 13273 eVL3 edge: 2p3/2 → 5d 11564 eV
Comparison with Lu et al.X-Ray Magnetic Circular Dichroism (XMCD)
XANES results for Pt
metallic Pt layer
no indication for oxidationor intermixing with Y3Fe5O12
Geprägs et al., arXiv:1307.4869 (2013)& Appl. Phys. Lett. 101, 262407 (2012)
XANES and XMCD in Pt|Fe
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)
no
rm. in
tensity (
a.u
.)
XANES
= 0.03 µB/Pt
Pt|Fe: ms = 0.03 µB/Pt
consistent with literaturevalues for Pt|Ni, etc…
1.2
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
-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
no
rm. in
ten
sity (
a.u
.)
Photon energy (eV)
XANES
XMCD
x100
< 0.003 µB/Pt
Normalized XANES and XMCD in Pt|Y3Fe5O12
from integrated XMCD signal:
Pt|Y3Fe5O12: ms < 0.003 µB/Pt
1.2
51
.25 EXAFS
wiggle
EXAFSwiggle
Pt L3 normalized whiteline intensity~1.25 a.u.→ compatible with metallic Pt
EXAFS wiggles at ~11587 eVand ~13299 eV→ characteristic for Pt metal
Kolobov et al., APL 86, 121909 (2005)
Our XMCD results
XMCD for Pt on Fe
XMCD for Y3Fe5O12 on Pt (“inverted” bilayer)
BUT: no finite XMCD for Pt on Y3Fe5O12
no magnetic proximity effect for Pt on Y3Fe5O12
XANES whiteline intensities
11550 11580 11610 13260 13290 13320 133500.0
0.5
1.0
1.5
-1%
0%
1%
2%L
2 edge
no
rm. X
AN
ES
(a.u
.)
Photon Energy (eV)
295 K
0.6 TPt(1.6nm)/YIG
YIG/Pt(10nm)
Pt L3 edge
XM
CD
Normalized XANES and XMCD in „inverted“ Y3Fe5O12|Pt
= 0.037 µB/Pt
1.2
5
EXAFSwiggle
EXAFSwiggle
from sum rules:
Pt|Y3Fe5O12: ms = 0
Y3Fe5O12|Pt: ms = 0.037 µB/Pt
Pt L3 normalized whiteline intensity~1.25 a.u.→ compatible with metallic Pt
EXAFS wiggles at ~11587 eVand ~13299 eV→ characteristic for Pt metal
intermixing with/incorporation into Y3Fe5O12
due to high energy of PLD particles?
European Synchrotron Radiation Facility(ESRF) Beamline ID12
Lu, …, Chien, PRL 110, 147207 (2013)
2.0
7
XAS/XMCD investigation of only one single sample
XAS whiteline = 2.07
no EXAFS wiggles detected
strong indication for non-metallic Pt
MPMR explanation questionable for Pt on Y3Fe5O12Lu et al.,
Phys. Rev. Lett. 110, 147207 (2013)
Lu et al. report XMCD for Pt on Y3Fe5O12, BUT:
Pt(1.5 nm)|YIG: ms = 0.054 µB/Pt @300K
YIG: LPE-grown, Pt: ex-situ sputtered