spintronics: how spin can act on charge carriers and vice versa tomas jungwirth university of...
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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