Spintronics: How spin can act on charge carriers and vice versa

Tomas Jungwirth

University of Nottingham

Institute of Physics Prague

Mott with spin current

Dirac with current through magnet

Mott without spin current

SpintronicsFrom Wikipedia, the free encyclopediaSpintronics (a pormanteau meaning spin transport electronics)....

Dirac without current through magnet

I I

I I

I I

MRAM2006

GMR1988

AMR1857

HD Read-heads1990‘s

I

I I

I

Mott with ferromagnets

Dirac with ferromagnets Dirac with antiferromagnets

I I

I I

Mott with antiferromagnets

Magnetic-field control of FMs:scales with current

Control by currentvia spin torques:scales with current density

0.1 pJ

Electro-static field control via relativisticmagnetic anisotropy effects:1fJ

(or piezo-electric)

Should work equally well or better in AFMs: more choices including SCs

Control by photo-carriers via spin torques:sub ps timescales

Relativistic spin-orbit torques might work equally well in AFMs plus photocarriers in SCs

Laser

Writing by currentvia spin torques:scales with current density

0.1 pJ

Writing by photo-carriers via spin torques:sub ps timescales

Relativistic spin-orbit torques might work equally well in AFMs plus photocarriers in SCs

Laser

Optical spin-transfer torque

Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492

M

M

sPn

OSTT

M

s

MPn

Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13

Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492

sPn

OSTT

M

s

MPn

Optical spin-transfer torque

Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13

Fernandez-Rossier, Nunez, Abofath, MacDonald cont-mat/0304492

sPn

OSTT

M

s

MPn

Optical spin-transfer torque

Němec, Tesařová, Novák, TJ et al. Nature Phys.’12, Nature Photonics ‘13, Nature Commun. ‘13

Zhang and Li PRL 2004Vanhaverbeke et al. PRB 2007,......

sPn

OSTT

M

Antidamping-like (adiabatic) STT

Electrical spin-transfer torque

s

MPn

Zhang and Li PRL 2004Vanhaverbeke et al. PRB 2007,......

Field-like (non-adiabatic) STT

Electrical spin-transfer torque

~

2)/(11

sex

2)/(1/

sex

sex

sexADNA STTSTT //

small in weakly SO-coupled dense-moment metal FMslarge in strongly SO-coupled dilute-moment (Ga,Mn)As

Antidamping-like STT Field-like STT

Electrical spin-transfer torque

Electrical spin-transfer torque: current induced DW motion

Zhang & Li, PRL 93, 127204 (2004)Vanhaverbeke & Viret, PRB 75, 024411 (2007)

vDW

j

= 0

jC

“intrinsic” pinning

Electrical spin-transfer torque: current induced DW motion

Antidamping STT

Antidamping-like STT

Zhang & Li, PRL 93, 127204 (2004)Vanhaverbeke & Viret, PRB 75, 024411 (2007)

vDW

jjC

<

Electrical spin-transfer torque: current induced DW motion

Antidamping-like STT

Field-like STT

Antidamping STT

Zhang & Li, PRL 93, 127204 (2004)Vanhaverbeke & Viret, PRB 75, 024411 (2007)

vDW

j

>

<

jCjC

Electrical spin-transfer torque: current induced DW motion

Antidamping-like STT

Antidamping STT

Field-like STT

Non-relativistic STT

External

Steady-state carrier spin polarization torque dtMd

s

QM averaging in non-equilibrium

Steady state

M

OSTT

nP

nP

Electrical spin injection

Optical spin injection

antidamping-like torque

Relativistic SOT

Internal

Steady-state carrier spin polarization torque dtMd

s

Steady state

M

(Ga,Mn)As OSOT

Optical spin injection

Electrical spin injection QM averaging in non-equilibrium

M

Relativistic SOT

Internal

Steady-state carrier spin polarization torque dtMd

s

Electrical drift and relaxation:broken inversion symmetry

ss

Optical generation and relaxation

Linear response: eigenstates of H & non-equilibrium distribution

s s

Steady state

ParamagnetsMagnetic field of moving nucleus

in electron‘s rest frame

Spin-orbit

s

Electrical drift and relaxation:broken inversion symmetry

Spin-galvanic effect

= SOT without acting on s

M

Aronov, Lyanda-Geller, JETP ’89, Edelstein SSC ’90, Ganichev et al. Nature ‘02

ParamagnetsMagnetic field of moving nucleus

in electron‘s rest frame

Spin-orbit

Spin Hall effect

Hall antidamping STT

Ralph, Buhrman,et al., Science ‘12

SHE in Pt acts as the external polarizer

MRAM switching by in-plane current SHE spin-current non-relativistic STT

MRAM switching by in-plane current attractive alternative to perp. current STT

Conventional perpendicular current STT

Conventional perpendicular current STT

MRAM switching by in-plane current attractive alternative to perp. current STT

Competing scenario: In-plane current swithing by relativitic SOT due to broken structural inversion symmetry at Co/Pt?

Miron et al., Nature ‘11

Ralph, Buhrman et al.: SHE Miron et al.: SOT

-We see antidamping-like torque

-SOT is field-like so we exclude it

- non-relativistic STT in metals is dominated by the antidamping torque

-We also see antidamping-like torque

-SOT is field-like but maybe there is some antidamping-like SOT as well

Where could a comparable strength antidamping-like SOT come from?