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