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

Tomas Jungwirth

University of Nottingham

Institute of Physics Prague

Fert, Grünberg, et al. 1988Nobel Prize 2007

Sloncyewski, Berger, 1996Buckley Prize at APS MM 2013

STT-MRAM

Reading by GMR (TMR) Writing by STT

Ie

Ie

Fert, Grünberg, et al. 1988Nobel Prize 2007

Read-out: non-relativistic giant magnetoresistance (GMR)

Fert, Grünberg, et al. 1988Nobel Prize 2007

Antiferromagnetic arrangement of a ferromagnetic multilayer at B=0

Read-out: non-relativistic giant magnetoresistance (GMR)

FM

FM

FM

FM

FM

FM

Soft FM

Hard FM

Soft FM

Hard FM

Fixed FM AFM

Soft FM

Fixed FMAFM

Soft FM

1. AFM coupling between FMs at B=0

3. One FM pinned by AFM material

Writing information in spin-valve: towards spintronic memory (MRAM)

2. One FM flips harder than the other FM

Fixed FM

NM

AFM

Soft FM

Towards reliable switching of a particular MRAM bit

Fixed FMAFM

FM

FM

Toggle switching first commercial MRAMs

“Synthetic AFM“

Spins injected from external polarizer in a non-uniform magnetic structure

MpM

Ie

Writing by current: non-relativistic spin-transfer torque (STT)

Sloncyewski, Berger, 1996Buckley Prize at APS MM 2013

MRAM: universal memory

Write with magnetic field:on market since 2006

Write with current (STT-MRAM):on market since 2013

scales with current

scales with current density

MRAM: universal memory Compatible with CMOS

GB MRAMs in few years

Conventional architecture with CMOS New architectuture with MRAM

kB

MB

GB

TB

hugegap

MRAM

Worldwide MRAM development

Spin-transistor

Datta, Das, APL 1990

Conventional architecture with CMOS New architectuture with spin-memory/logic

Ie

Ie

Fert, Grünberg, et al. 1988Nobel Prize 2007

Read-out: non-relativistic giant magnetoresistance (GMR)

M

Kelvin, 1857

Ie

Read-out: relativistic anisotropic magnetoresistance (AMR)Spintronic effect 150 years ahead of time

M

Ie

Kelvin, 1857

Read-out: relativistic anisotropic magnetoresistance (AMR)Spintronic effect 150 years ahead of time

“Mott“ non-relativistic two-spin-channel model of ferromagnets

“Dirac“ relativistic spin-orbit coupling

I

I I

I

Mott, 1936

Dirac, 1928

Two paradigms for spintronics

Spin-orbit coupling

nucleus rest frame electron rest frame

vI Q rE3

04 r

Q

3

0

4 r

rIB

EvEvB 200

1

c EvSS

2B

mc

egH BSO

Lorentz transformation Thomas precession

2 2

Spin-orbit coupling: quantum relativistic physics

),(2

),(

2

1

2

2

22

22

trrm

trt

i

mvm

pE

)/1(/1

,

22

02

cv

mmmcE

Spin-orbit coupling: quantum relativistic physics

Dirac equation

Spin-orbit coupling: quantum relativistic physics

spcE

spin and orbital motion coupled

Ultra-relativistic quantum particles (neutrino)

Dirac equation

spin and orbital motion coupled

Ultra-relativistic quantum particles (neutrino)

spcE

Dirac equation

spin and orbital motion coupled

Ultra-relativistic quantum particles (neutrino)

spcE

Dirac equation

Ohmic “Dirac“ device: AMR

Magnetization-orientation-dependent scattering

Kelvin, 1857

Ohmic “Mott“ device: GMR

Spin-channel-dependent scattering

Fert, Grünberg, 1988

Tunneling “Mott“ device: TMR

MRAM

Spin-channel-dependent tunneling DOS

Julliere 1975, Moodera et al., Miyazaki & Tezuka 1995

Tunneling “Dirac“ device: TAMR

Gould, TJ et al. PRL ‘04

Magnetization-orientation-dependent tunneling DOS

Chemical potential controlled “Dirac“ device

Wunderlich, TJ et al. PRL ‘06

Magnetization-orientation-dependent chemical potential

++

--

MagnetDielectric

Non-magneticchannel

M

Chemical potential of magnetic gate changes

Charge on magnetic gate changes

Polarisation charge on non-magnetic channel

II

Dirac spintronic device without current through magnet

Ciccarelli, Ferguson, TJ et al. APL ‘12

MagnetDielectric

Non-magneticchannel

++

--

M

Chemical potential of magnetic gate changes

Charge on magnetic gate changes

Polarisation charge on non-magnetic channel

II

Dirac spintronic device without current through magnet

Ciccarelli, Ferguson, TJ et al. APL ‘12

MagnetDielectric

Non-magneticchannel

+++

---M--

++

Chemical potential of magnetic gate changes

Charge on magnetic gate changes

Polarisation charge on non-magnetic channel

II

Dirac spintronic device without current through magnet

Ciccarelli, Ferguson, TJ et al. APL ‘12

DVg = Dm/e

Ciccarelli, Ferguson, TJ et al. APL ‘12

Dirac spintronic device without current through magnet

Inverted approach to spin-transistorDirect approach to spin-transistor

Inverted approach to spin-transistorDirect approach to spin-transistor

Inverted approach to spin-transistorDirect approach to spin-transistor

Inverted approach to spin-transistorDirect approach to spin-transistor

Inverted approach to spin-transistorDirect approach to spin-transistor