Part 2

Report
Spintronics: How spin can act on charge carriers and vice versa
Tomas Jungwirth
Institute of Physics Prague
University of Nottingham
Mott without spin current
Mott with spin current
I

Spintronics
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From Wikipedia, the free encyclopedia
Spintronics (a pormanteau meaning
spin transport electronics)....
GMR
1988
MRAM
2006
Dirac without current through magnet
Dirac with current through magnet
I
AMR
1857
I
HD Read-heads
1990‘s
Writing by current: non-relativistic spin-transfer torque
Spins injected from external polarizer in a non-uniform magnetic structure
Mp
M
Ie
Berger PRB ’96, Slonczewski JMMM ’96
STT-MRAM
Writing by current: non-relativistic spin-transfer torque
Spins injected from external polarizer in a non-uniform magnetic structure
Mp
M
Ie
Berger PRB ’96, Slonczewski JMMM ’96
Mott
I
I
Writing by current: relativistic spin-orbit torque
Spin current in a uniform magnetic structure with broken space-inversion symmetry
M
Ie
Manchon & Zhang, PRB ‘08, Chernyshev et al. Nature Phys.‘09,
Miron et al. Nature Mater. ‘10, Fang, Ferguson, TJ et al. Nature Nanotech.‘11
Zinc-blende (Ga,Mn)As:
broken bulk inversion symmetry
In-plane current switching
Miron et al., Nature ‘11
Co/Pt: broken structural inversion symmetry
Writing by current: relativistic spin-orbit torque
Spin current in a uniform magnetic structure with broken space-inversion symmetry
M
Ie
Manchon & Zhang, PRB ‘08, Chernyshev et al. Nature Phys.‘09,
Miron et al. Nature Mater. ‘10, Fang, Ferguson, TJ et al. Nature Nanotech.‘11
Dirac
Zinc-blende (Ga,Mn)As:
broken bulk inversion symmetry
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I
Materials
Paramagnets: very frequent
Disordered M=0: bad for direct manipulation by magnetic field,
no magnetic memory
compatible with semiconductors: transitsors & photonics
Spin Hall effect
Kato et al., Science ’04, Wunderlich, TJ et al. Phys. Rev. Lett. ’05
Spin-orbit
Magnetic field of moving nucleus
in electron‘s rest frame
Paramagnets: very frequent
Disordered M=0: bad for direct manipulation by magnetic field,
no magnetic memory
compatible with semiconductors: transitsors & photonics
Spin Hall effect
Spin-orbit
Magnetic field of moving nucleus
in electron‘s rest frame
Paramagnets: very frequent
Disordered M=0: bad for directmanipulation by magnetic field,
no magnetic memory
compatible with semiconductors: transitsors & photonics
Spin-orbit
Antiferromagnets: frequent
Magnetic field of moving nucleus
in electron‘s rest frame
Ordered M=0: bad for direct manipulation by magnetic field,
good for retention with magnetic field around
compatible with semiconductors: transitsors & photonics
Ferromagnets: rare
Eexchange
Ordered M0: good for direct manipulation by magnetic field,
bad for retention with magnetic field around
not well compatible with semiconductors
Egap
EFermi
Magnetic-field control of FMs:
scales with current
Control by current
via spin torques:
scales with current
density
Control by photo-carriers
via spin torques:
sub ps timescales
0.1 pJ
Relativistic spin-orbit torques
might work equally well in
AFMs plus photocarriers in SCs
Electro-static field control via relativistic
magnetic anisotropy effects:
1fJ
Should work equally well or better
in AFMs: more choices including SCs
(or piezo-electric)
Mott with antiferromagnets
Mott with ferromagnets
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I
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Dirac with ferromagnets
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
I
Dirac with antiferromagnets
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I
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Spintronics with antiferromagnets
AFM IrMn
Dirac
I
I
FM
AFM
 2
 AMR ~ (m) 
Shick, Wunderlich, TJ, et al., PRB‘10
Spin-valve with AFM electrode
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
Pt
NiFe
MgO
NiFe
MnIr
Ta/Ru/Ta
Spin-valve with AFM electrode
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
Pt
MgO
NiFe
MnIr
Ta/Ru/Ta
NiFe
Spin-valve with AFM electrode
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
Pt
MgO
MnIr
NiFe
Ta/Ru/Ta
Spin-valve with AFM electrode
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
100
1.5 & 3nm IrMn
R [k]
Pt
MgO
MnIr
50
NiFe
Ta/Ru/Ta
-1
4K
0
B[T]
1
>100% spin-valve-like signal at ~50 mT
Spin-valve with AFM electrode
Pt
MgO
MnIr
R (kohm)
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
80
60
40
NiFe
Ta/Ru/Ta
20
-1000
-500
0
Field (Oe)
500
Electrically measurable memory effect in AFM
Spin-valve with AFM electrode
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
Pt
MgO
MnIr
NiFe
R (kohm)
Ta/Ru/Ta
80
60
40
20
-100
-50
0
Field (mT)
50
Small signal in control sample without IrMn
Spin-valve with AFM electrode
I
Park, Marti, Wunderlich,TJ et al. Nature Mat. ’11, PRL ’12
Writing by magnetic field via FM/AFM exchange-spring
I
B
~100% AFM-TAMR
AFM memory effect
50
-1
[o]
R (k)
R [k]
100
0
B[T]
1
80
60
40
20
-100
Wang et al. PRL ’12: room-T AFM TAMR in CoPt/IrMn/AlOx/Pt
-50
0
B [mT]
50
AFM tunnel junction written by field-cool without FM
Petti, Marti, Bertacco, TJ et al., submitted to APL ‘13
Pt
MgO
MnIr
NiFe
Ta/Ru/Ta
AFM tunnel junction written by field-cool without FM
Petti, Marti, Bertacco, TJ et al., submitted to APL ‘13
Pt
MgO
MnIr
NiFe
Ta/Ru/Ta
AFM tunnel junction written by field-cool without FM
Petti, Marti, Bertacco, TJ et al., submitted to APL ‘13
Pt
MgO
MnIr
Ta/Ru/Ta
Compare:
thermal-assisted MRAM
AFM tunnel junction written by field-cool without FM
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Petti, Marti, Bertacco, TJ et al., APL ‘13
Principle: increase susceptibility  write by field  back to negligible susceptibility AFM
I
z
Pt
MgO
B
x
y
MnIr
(RH-RL)/RL (%)
Ta/Ru/Ta
Magnetic memory insensitive to magnetic fields & producing no stray fields
Control by electro-static fields or photo-carriers: magnetic semiconductors
Spintronics & transistors
Spintronics & photonics
M
Tc < room-T
Ohno, Dietl et al., Science ’98,’00, TJ et al., Rev. Mod. Phys. ‘06
Magnetic semiconductors: more AFMs than FMs and high-TN AFMs
TJ, Novák, Martí et al. PRB ’11, Cava Viewpoint, Physics ’11, Máca, Mašek, TJ et al. JMMM ’12
AFM TN (K)
III-V
MnO
122
FeN
100
MnS
152
FeP
115
MnSe
173
FeAs
77
MnTe
323
FeSb
100-220
II-VI
FM TC (K)
FM TC (K)
AFM TN (K)
EuO
67
GdN
72
EuS
16
GdP
15
EuSe
5
GdAs
19
EuTe
10
GdSb
27
AFM TN (K)
II-V-IV-V
CuFeO2
11
MnSiN2
CuFeS2
825
I-II-V
CuFeSe2
70
CuFeTe2
254
Ia=Li, Na,..
Ib=Cu
II=Mn
V=Sb,As, P
I-VI-III-VI
FM TC (K)
FM TC (K)
AFM TN (K)
490
FM TC (K)
AFM TN (K)
> room T
Spin-orbit-coupled Mott AFM semiconductor
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Kim et al., Science ’09, two focused sessions at APS MM 2013
Ohmic AMR in Sr2IrO4 AFM semiconductor
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Writing by magnetic field via
FM/AFM exchange-spring
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B
3000
R13
R23
10
I (A)
R ()
2000
1000
T = 4.2 K
0
Martí, TJ, Fontcuberta, Ramesh,
et al. preprint
-10
-20
0
0
0
V (mV)
100
200
T (K)
20
300
Ohmic AMR in Sr2IrO4 AFM semiconductor
Pt
SIO
Ag
Ag
LSMO
R/R (%)
1
T = 200 K
0
-1
0
0
90 180 270 360
R/R (%)
1
-1
0
90 180 270 360
0
90 180 270 360
0
90 180 270 360
 (°)
1
T = 40 K
0
-1
0
0
90 180 270 360
1
R/R (%)
Ag
LSMO
1
Martí, TJ, Fontcuberta, Ramesh,
et al. preprint
SIO
-1
1
T = 4.2 K
0
-1
0
0
90 180 270 360
 (°)
-1

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