Part 1

Report
Spintronics: How spin can act on charge carriers and vice versa
Tomas Jungwirth
Institute of Physics Prague
University of Nottingham
STT-MRAM
Reading by GMR (TMR)
Fert, Grünberg, et al. 1988
Nobel Prize 2007
Writing by STT
Sloncyewski, Berger, 1996
Buckley Prize at APS MM 2013
Read-out: non-relativistic giant magnetoresistance (GMR)
Ie
Ie
Fert, Grünberg, et al. 1988
Nobel Prize 2007
Read-out: non-relativistic giant magnetoresistance (GMR)
Fert, Grünberg, et al. 1988
Nobel Prize 2007
Antiferromagnetic arrangement of a ferromagnetic multilayer at B=0
Writing information in spin-valve: towards spintronic memory (MRAM)
1. AFM coupling between FMs at B=0
FM
FM
FM
FM
FM
FM
2. One FM flips harder than the other FM
Soft FM
Soft FM
Hard FM
Hard FM
3. One FM pinned by AFM material
Soft FM
Soft FM
Fixed FM
AFM
Fixed FM
AFM
Towards reliable switching of a particular MRAM bit
Soft FM
NM
Fixed FM
AFM
Toggle switching  first commercial MRAMs
“Synthetic AFM“
FM
FM
Fixed FM
AFM
Writing by current: non-relativistic spin-transfer torque (STT)
Spins injected from external polarizer in a non-uniform magnetic structure
Mp
M
Ie
Sloncyewski, Berger, 1996
Buckley Prize at APS MM 2013
MRAM: universal memory
Write with magnetic field:
on market since 2006
scales with current
Write with current (STT-MRAM):
on market since 2013
scales with current density
MRAM: universal memory
Compatible with CMOS
GB MRAMs in few years
Conventional architecture with CMOS
New architectuture with MRAM
MRAM
kB
MB
huge
gap
GB
TB
Worldwide MRAM development
Spin-transistor
Datta, Das, APL 1990
Conventional architecture with CMOS
New architectuture with
spin-memory/logic
Read-out: non-relativistic giant magnetoresistance (GMR)
Ie
Ie
Fert, Grünberg, et al. 1988
Nobel Prize 2007
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
M
Ie
Kelvin, 1857
Two paradigms for spintronics
“Mott“ non-relativistic two-spin-channel model of ferromagnets
I
I
Mott, 1936
“Dirac“ relativistic spin-orbit coupling
I
Dirac, 1928
I
Spin-orbit coupling
nucleus rest frame
electron rest frame
I  Qv
1
B   0 0 v  E  2 v  E
c
Lorentz transformation  Thomas precession
H SO
E
Q
4 0 r
3
r
0 I  r
B
4 r 3
g B
e

SB 
SvE
2
2
2mc
Spin-orbit coupling: quantum relativistic physics
p2
1
E 

m v2
2m
2


i
 (r , t ) 
t

2 2


(
r
, t)
2m r 2
Spin-orbit coupling: quantum relativistic physics
E  m c2 , m  m0
  1 / (1  v 2 / c 2 )
Dirac equation
Spin-orbit coupling: quantum relativistic physics
Ultra-relativistic quantum particles (neutrino)
Dirac equation
 
E  cp  s
spin and orbital motion coupled

Ultra-relativistic quantum particles (neutrino)
Dirac equation
 
E  cp  s
spin and orbital motion coupled

Ultra-relativistic quantum particles (neutrino)
Dirac equation
 
E  cp  s
spin and orbital motion coupled


Ohmic “Dirac“ device: AMR
Kelvin, 1857
Magnetization-orientation-dependent scattering
Ohmic “Mott“ device: GMR
Fert, Grünberg, 1988
Spin-channel-dependent scattering
Tunneling “Mott“ device: TMR
Julliere 1975, Moodera et al., Miyazaki & Tezuka 1995
MRAM
Spin-channel-dependent tunneling DOS
Tunneling “Dirac“ device: TAMR
Gould, TJ et al. PRL ‘04
Magnetization-orientation-dependent
tunneling DOS
Magnetization-orientation-dependent
chemical potential
Chemical potential controlled
“Dirac“ device
Wunderlich, TJ et al. PRL ‘06

Dirac spintronic device without current through magnet

Chemical potential of magnetic gate changes
Charge on magnetic gate changes
Polarisation charge on non-magnetic channel
Magnet
Dielectric
Non-magnetic
channel
Ciccarelli, Ferguson, TJ et al. APL ‘12

M
-
+
+
Dirac spintronic device without current through magnet

Chemical potential of magnetic gate changes
Charge on magnetic gate changes
Polarisation charge on non-magnetic channel
Magnet
Dielectric
Non-magnetic
channel
Ciccarelli, Ferguson, TJ et al. APL ‘12

M
-
+
+
Dirac spintronic device without current through magnet

Chemical potential of magnetic gate changes
Charge on magnetic gate changes
Polarisation charge on non-magnetic channel
Magnet
Dielectric
Non-magnetic
channel
Ciccarelli, Ferguson, TJ et al. APL ‘12

M
-
+
+
+
+
+
Dirac spintronic device without current through magnet
Vg = /e
Ciccarelli, Ferguson, TJ et al. APL ‘12
Direct approach to spin-transistor
Inverted approach to spin-transistor
Direct approach to spin-transistor
Inverted approach to spin-transistor
Direct approach to spin-transistor
Inverted approach to spin-transistor
Direct approach to spin-transistor
Inverted approach to spin-transistor
Direct approach to spin-transistor
Inverted approach to spin-transistor

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