2018.06.12 jairo sinova jgu

!1Nano-front Magnetism —Madrid — Jairo Sinova
12th of June 2018
Jairo Sinova
Johannes Gutenberg Universität Mainz
Smejkal, Zelezny, Sinova, Junwirth PRL (2017)
Smejkal, Jungwirth, Sinova PSS (2017)
Jairo Sinova and Tomas Jungwirth, Physics Today (2017)
Bodar, Smejkal, Jourdan, Kläui, JS, et al, Nature Comm. (2018)
Jungwirth, JS, et al, Nature Physics (AFM spintronics Reviews) (2018)
Topological Antiferromagnetic Spin-orbitronics:
from spin Hall effect, to spin-orbit torques,
to Néel spin-orbit torques, to tunable Dirac fermions
Olejnik, Jugwirth, Kampfrad, JS, et al - Science Advance 2018

I. Spin-Orbit Torques in Ferromagnets and Antiferromagnets:
•SHE and Inverse spin galvanic effect phenomenology
•Spin-orbit Torques
•Néel Spin-orbit Torque
II.Topological Dirac Fermion + Antiferromagnets + Neel SOTs
III.AHE in collinear AFMs
Kurebayashi, et al., Nat. Nanot. (2014)
Zelezny, Gao, JS, Jungwirth PRL (2014)
Zelazny, Gao, et al. PRB (2016)
Gomonay, Jungwirth, Sinova PRL (2016)
Yu, Smejkal, Jourdan, Kläui, JS, et al, arXiv: 1706.02482 (2017)
Sinova,et al RMP (2015)
Ciccarelli, et al., Nat. Phys. (2016)
Topological Antiferromagnetic Spin-orbitronics:
Surprises of the Spin Hall Effect, Physics Today 70, 7, 38 (2017)

!3
Hilbert et al. Science (2011)
Analog
to
Digital
Gutenberg
(1400-1468)
1015
1014
1013
1012
1986 1993 2000 2007
Digital: Hard-disks, DVDs,…
Analog: books, video/film, …
MB
Analog to digital = Ink to Spin
Nano-front Magnetism —Madrid — Jairo Sinova

Discovery of Giant Magneto Resistance
Albert Fert Peter Grünberg
GMR first observed in 1988
From fundamental to practical
Stuart Parkin
2014 Humboldt Professor
and 2014 Millennium Prize
Low Resistance High Resistance

What is next in memory storage?
Spin-Transfer
MRAM
(2015)
Heating Problems
MRAM
Magnetic Random
Access Memory
First generation did NOT
combine charge and spin

Magnetization dynamics and Spin Transfer Torque
d ˆM
dt
= ˆM ⇥ ~Heff + ↵ ˆM ⇥
d ˆM
dt
+
~PJ
2e
( ˆM ⇥ ˆM0) ⇥ ˆM
(proposed by Slonczewski, Berger 1996)
Ferro 1 Ferro 2Spacer
Torque
Spin Transfer Torque

Spin-Transfer-Torque MRAM
Spin-Transfer-Torque MRAM
MTJ
STT mechanism:
~ 30 μA
• excellent scaling
• lower power
• no crosstalk problem
• simpler fabrication
3"

in-plane-current switching MRAM
MTJ
In-plane-current-switching MRAM
If switching can be done by an
in-plane current then a key
issue in STT-MRAM is resolved
4"

Control of materials properties via spin-orbit coupling
Antiferro
magnetic
materials
Nano-
transport
Spintronic
Hall effects
Topological
transport
effects
Spin-
orbitronics
Caloritronics
Spin-orbit
Torques
Spin-orbitronics

Inverse Spin Galvanic Effect or Edelstein Effect
Spin-current and spin-polarization generation by currents
(Reverse process of circular photo-galvanic effect, Ganichev et al., 2001)
Wunderlich et at. arXiv ‘04, PRL ‘05
Spin Hall Effect in p-GaAs

[100]
[010]
Intrinsic spin-Hall effect: the Rashba SOC example
+sz
-sz
~Beff (~k) / ~seq
Δp ∼ eEt
~E
Beff ⇠ pˆy
~E
ky [010]
kx [100]
S=0
HR =
~2
k2
2m
µB~ · ~Beff (~k)
=
~2
k2
2m
+ ↵R( xky ykx)

Inverse Spin Galvanic Effect or Edelstein Effect
kx
ky
δS=0δSy≠0
J || x
Wunderlich, Jungwirth, JS, et al PRL/PRB 2003/2004
Current induced polarization

Experiments of in-plane current magnetic switching
Miron et al., Nature ‘11
Buhrman,et al., Science ‘12
spin-orbit torque at PM/FM interface
intrinsic SHE + STT
SHE as spin-current generator + STT
d ~M
dt
!
SHE ST T
= P ˆM ⇥ (ˆn ⇥ ˆM)
d ~M
dt
!
SOT
=
Jex
~
~M ⇥ ~s
hSOT || z × J
Jairo Sinova and Tomas Jungwirth, Physics Today (2017)

SpinHall Rashba
Courtesy of P. Gambardella
Spin-orbit Torques in Bilayer Systems
Make a ferromagnet behave like a cat:
SOC (broken bulk inversion)+ferromagnetism
?

[100]
[110]
[010]
[100]
[110]
[010]
Dresselhaus
GaMnAs
GaAs
GaMnAs
Intrinsic (Berry phase) spin-orbit torque in GaMnAs
Rashba
d ˆM
dt
!
SOT
= ˆM ⇥ sz(✓M E)ˆz
current direction
angle between M and
current direction
Kurebayashi, JS, et al.,
Nat. Nanot. (2014)

90 180 270
-150
-100
-50
0
50
100
150
µ0
hz
[µT]
[100]
90 180 270
-150
-100
-50
0
50
100
150
[010]
0 90 180 270 360
θM-J
-150
-100
-50
0
50
100
150
µ0
hz
[µT]
[1-10]
90 180 270 360
θM-J
-150
-100
-50
0
50
100
150
[110]
Discovery of anti-damping spin-orbit torques
Solid line: Calculations with HKL (captures higher harmonics)
S // M
[100]
[010]
Kurebayashi, JS, et al., Nat. Nanot. (2014)

Antiferromagnetic Spintronics
17Nano-front Magnetism —Madrid — Jairo Sinova
Spin not charge based
Radiation-hard
Ordered spins
Non-volatile
No net moment
Insensitive to magnetic fields,
no fringing stray fields
THz dynamics
Ultra-fast switching
Multiple-stable domain configurations
Memory-logic bit cells
Materials range
Insulators, semiconductors, semimetals,
metals, superconductors
Last issue of the
International Technological
Roadmap for
Semiconductors in 2016

Writing by spin-orbit torque in a single-layer ferromagnet
Magnet reversing itself : SOT
Antiferromagnetic Spin-orbitronics
AFM
Néel SOT
J. Zelezny, H. Gao, K. Vyborny, J. Masek, J. Zemen, A. Manchon, J. Sinova, and T. Jungwirth, PRL (2014)

Antiferromagnet with broken sublattice space-inversion symmetry: (Mn2Au)
Writing by Néel spin-orbit torque in a single-layer antiferromagnet
kx
ky
kx
ky
S=0
S=0
Sy≠0
Sy≠0
J || x
HSOT || z × J
HSOT || -z × J
Zelezny, Gao, Jungwirth,
JS PRL 2004

Antiferromagnet with broken sublattice space-inversion symmetry: (Mn2Au)
By
A
By
B
Bx
B
Bx
A
0 45 90 135 180
Φ (Degrees)
B(mT)(per107A/cm2)
0.4
0.2
0
-0.2
-0.4
-90 -45 0 45 90
θ (Degrees)
B(mT)(per107A/cm2)
0.3
0.1
0
-0.1
-0.3
Bx
A
Bx
B
By
B
Bz
B
By
A
Bz
A
J || x
Zelezny, Gao, Jungwirth, JS
December PRL (2014)
Writing by Néel spin-orbit torque in a single-layer antiferromagnet

!21
How it works - kind of
Nano-front Magnetism —Madrid — Jairo Sinova

Experimental Observation of Néel SOT in CuMnAs
!22Nano-front Magnetism —Madrid — Jairo Sinova0.4
0.8
!0.05
0.00
0.05
(
/cm
3
)
(
(
20
40
4.4)kO e)applied)No)field)applied
!30
0
30
$
$
$
ΔRt
(mΩ)
0 20 40 60 80 100 120 140 160
!30
0
30
$P uls e$number
$
$
ΔRt
(mΩ)
A" B"
C" D"
5 6 7 8 9 10
0
10
20
30
40
+
+
ΔRt+
(mΩ) S etting+current+dens ity+(MA/cm
2
)
A" B" 1" 2"
3"
4"5"6"
7"
8"CuMnAs"
GaP"
C" D"
0 2 4 6 8 10
'10
0
10
(
(
ΔRt
((mΩ)
P uls e(number
0 2 4 6 8 10
'10
0
10
(
(ΔRt
((mΩ)
(
P uls e(number
!0
!0
0
0
0
Moment((emu/cm
3
)
0 2 4 6 8 10 12
'40
'20
0
20
40
4.4)kO e)applied
)
)
ΔRt
(mΩ)
P uls e)number
No)field)applied
0 20 40 60 80 100 120 140 160
!30
$P uls e$number
Figure"4""
(A)"Transverse"resistance"using"orthogonal"probe"curren
(black)"and"3H7"(red)."(B)"Dependence"of"the"change"in"t
density"of"the"seUng"pulse."The"dashed"line"is"a"guide"to
resistance"aFer"current"pulses"alternately"along"orthogo
1H6)"and"with"4.4"kOe"ﬁeld"applied"(pulses"7H12)."(D)"Ma
measured"by"SQUID"magnetometer."
"
C" D"
5
0
Setting 1-5
Setting 3-7
CuMnAs
A
B
Rashba field:
B ~ 3 mT per 107 Acm-2
Wadley, Jungwirth, et al Science (2016)
AMR correspondance to Neel switching veriﬁed by
X-ray MLD photoemission electron microscopy

From prediction, to observation, to device in 1 one year!!
Works like this but
not done like this
Electrical read/write antiferromagnetic memory
Wadley, Jungwirth et al. Science ’16, Jungwirth, Marti, Wadley, Wunderlich, Nature Nanotech. ’16

Experimental Observation of Néel SOT in Mn2Au
●
●
●
●
●
■
■
■
■
■
● Mn-Au
■ Au
0 1 2 3 4 5
0
10
20
30
Disorder/%
ρ/μΩcm
■
■
■
■
□ □ □ □ □
●
●
●
●
●
○
○ ○ ○ ○
■ Au [100]
□ Au [110]
● Mn-Au [100]
○ Mn-Au [110]
0 1 2 3 4 5
0
1
2
3
4
5
6
Disorder/%
AMR/%
[100] [010]
[001]
Experiment
Experiment
0.6+-0.3% Au rich,
Mn-Au <5%
Experiment:
S.Bodnar et al.*,
(2.5-6 %),
M.Meinert et al,
arXiv.1706.06983
(5 %D: App.Phys)
M.Jourdan et al.,
JoP . (2015): 8
μΩcm
H.Wu et al., AFM
(2016) (1-2.5 %)
Relativistic DFT:
Bodnar, Smejkal, Jourdan, Kläui, Jungwirth, JS, et al, Nature Communications (2018)

Anisotropic spectral function and stability of Dirac points
CPA preserves the symmetry prevented hybridisations
Disorder propagates Dirac point to Fermi level and shifts the Fermi level
E(k) ! A(E, k) =
1
⇡
ImG
kx
-1.5
-1
-0.5
0
0.5
Energy/eV
M Γ
[100]
[010]
Angular dependence of Bloch spectral function
⇢k > ⇢?
AMR > 0
n||[010]n||[100]
⇢?
⇢k
-1.5
-1
-0.5
0
0.5
Energy/eV
M Γ
[100]
[010]
Bodnar, Smejkal, Jourdan, Kläui, Jungwirth, JS, et al, Nature Communications (2018)

CuMnAs
THz writing speed 𝟏/𝝉 𝒑 in antiferromagnetic memory
CuMnAs
2μm
THz writing speed !/#$ in antiferromagnetic memory
Contact μs-pulse electrical writing
Non-contact ps-pulse electrical writing
E
1/'( ≈ MHz
1/'( ≈ THz
Olejnik, TJ et al., unpubl.
Olejnik, Jungwirth, Kampfrad, JS, et al - Science Advance 2018

THz writing speed 𝟏/𝝉 𝒑 in antiferromagnetic memory
Non-contact electrical writing with 1/#$ = THz pulses
THz writing speed */+, in antiferromagnetic memory
Transverse AMR
readout
V
V
V
V
Contact electrical writing with 1/#$ = MHz pulses
Olejnik, TJ et al., unpubl.
!~10%
Acm*+
@ 1/./~ GHz
Olejnik, Jungwirth, Kampfrad, JS, et al - Science Advance 2018

I. Spin-Orbit Torques in Ferromagnets and Antiferromagnets:
•SHE and Inverse spin galvanic effect phenomenology
•Spin-orbit Torques
•Néel Spin-orbit Torque
II.Topological Dirac Fermion + Antiferromagnets + Neel SOTs
III.AHE in collinear AFMs
Kurebayashi, et al., Nat. Nanot. (2014)
Zelezny, Gao, JS, Jungwirth PRL (2014)
Zelazny, Gao, et al. PRB (2016)
Gomonay, Jungwirth, Sinova PRL (2016)
Yu, Smejkal, Jourdan, Kläui, JS, et al, arXiv: 1706.02482 (2017)
Sinova,et al RMP (2015)
Ciccarelli, et al., Nat. Phys. (2016)
Topological Antiferromagnetic Spintronics:
Surprises of the Spin Hall Effect, Physics Today 70, 7, 38 (2017)

2003
2017
SHE
QSHE
2D TI
graphene
SOT
3D TI
Dirac/Weyl
semimetals
Néel SOT

Coexistence of Topological Dirac fermions and Néel
Can we control the relativistic fermions electrically?
?
+
Smejkal, Zelezny, Sinova, Jungwirth PRL (2017)

Model of AFM topological semimetal
[001] δs
A
δs
BA
B
[100]
[010]
J
YES!
Overlap of symmetry conditions
Dirac fermions AF spintronics
?
+
1. Two sites in unit cell
band crossing inversion-partner sites
→ staggered field
PT2. symmetry
Double band degeneracy
→ Dirac point
AF spin-sublattices
at inversion partner sites

Minimal lattice model: construction
Kane-Mele spin-orbit coupling
A
B
A
B

Minimal lattice model: band structure
Renormalization: 2D Dirac points —> 3D nodal lines
D2D1

Minimal lattice model: local symmetries
P
PT + A, B noncentrosymmetric
P
Neel spin-orbit torque
z
x
Pseudovector/axial vector
PT

Symmetry protection of Dirac points
[100]
[010]
Mirror Translate
nonsymmorphic symmetry = point group + nontrivial translation
glide mirror plane Gx={Mx/(1/2,0,0)} Mx
at Gx invariant
subspace

Electrical control of Dirac fermions
Nonsymmorphic symmetry:
Screw axis+Glide plane
Demonstration of inplane Field like torque manipulation
Demonstration of (001) ! inplane Field like torque
tetra.
ortho.

Topological magnetotransport: AMR

Néel SOT in a single-
layer antiferromagnet
SUMMARY
SOT in a single-layer
ferromagnet
M MB −~eq
eff
Beff ⇠ pˆy
~E
Kurebayashi, et al.,
Nature Nanotech (2014)
JS,Valenzuela, Wunderlich, Back,
Jungwirth RMP (2015)
SHE and ISGE
Wadley, et al Science (2016)
Neel SOT physics (ii)Topological Dirac
Semi Metal+ AFM (i)
Topological Antiferromagnetic
Spin-orbitronics
Kurebayashi, et al.,
Nature Physics (2016)
Libor Smejkal, et al PRL (2017) and PSS (2017)
J. Zelezny, et al, PRL (2014)
J. Zelezny, et al, PRB (2016)
O. Gomonay, et al, PRL (2016)
Yu, et al. arXiv: 1706.02482 (2017)
AHE in RuO2 (col-AFM)(iii)

Smejkal, Zelezny, Gyles, Ciccarelli, Kläui, Gomonay, Wadley, Kampfrath, Jungwirth
Univ. of NottinghamInstitute of Physics Prague Univ. of Cambridge
MPI - Berlin

40
3rd-7th of September 2018 - Mainz, Germany
9th
JEMS Conference 2018
Joint European Magnetic Symposia

2018.06.12 jairo sinova jgu

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