Antiferromagnetic Spintronics - School of...
Transcript of Antiferromagnetic Spintronics - School of...
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Lecture II
Antiferromagnetic‐Spintronics
Alireza QaiumzadehRadboud University (RU)
Institute for Molecules and Materials (IMM)Theory of Condensed Matter group (TCM)
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Louis Néel(1904‐2000)
AntiferromagnetismL. Néel, Ann. de physique (Paris), 17, 63 (1932).L. Néel, Ann. de physique (Paris), 5, 232 (1936) .F. Bitter, Phys.Rev., 54, 79 (1938).
FerrimagnetismL. Néel, Ann. de physique (Paris), 3 , 137 (1948) .
Nobel Lectures in Physics
Interesting but useless!
T. Jungwirth et al. arXiv: 1509.05296
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Ordered M0: good for direct manipulation by magnetic field, bad for retention with magnetic field aroundnot well compatible with semiconductors
Ferromagnets: rare
Disordered M=0: bad for directmanipulation by magnetic field, no magnetic memory compatible with semiconductors: transitsors & photonics
Paramagnets: very frequent
Antiferromagnets: frequent
Ordered M=0: bad for direct manipulation by magnetic field, good for retention with magnetic field aroundcompatible with semiconductors: transitsors & photonics
Egap
Eexchange
EFermi
Jungwirth
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I. Introduction
II. AFM-LLG equation
III. AFM Domain Wall dynamics (AFM-DWs)
OUTLINE
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1. Introduction
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II‐VI FM TC (K) AFM TN (K)
MnO 122
MnS 152
MnSe 173
MnTe 323
EuO 67
EuS 16
EuSe 5
EuTe 10
II‐V‐IV‐V FM TC (K) AFM TN (K)
MnSiN2 490
III‐V FM TC (K) AFM TN (K)
FeN 100
FeP 115
FeAs 77
FeSb 100‐220
GdN 72
GdP 15
GdAs 19
GdSb 27
I‐VI‐III‐VI FM TC (K) AFM TN (K)
CuFeO2 11
CuFeS2 825
CuFeSe2 70
CuFeTe2 254
I‐II‐V FM TC (K) AFM TN (K)
Ia=Li, Na,..Ib=CuII=MnV=Sb,As, P
> room T
Magnetic semiconductors: more AFMs than FMs and high-TN AFMs Jungwirth, Novák, Martí et al. PRB ’11, Cava Viewpoint, Physics ’11, Máca, Mašek, TJ et al. JMMM ’12
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FM AFM
Shick, Wunderlich, Jungwirth, et al., PRB‘10
Spintronics with antiferromagnets
AFM IrMn
2)(~ mAMR
I I
Dirac
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2. AFM-LLG equation
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Hals et al. PRL. 106, 107206 (2011)
Phenomenology of Current‐Induced Dynamics in Antiferromagnets
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Dynamics of AFMs obeys the second law of Newton: Inertia motion
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The non‐inertial mechanism requires a continuous driving force that pulls the mass over the potential barrier. A similar scenario is realized in magnetization reversal through precessional motion in ferromagnets. In contrast, in the inertial mechanism, during the action of the driving force the coordinate of the particle is hardly changed,but the particle acquires enough momentum to overcome the barrier afterwards.
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3. AFM Domain Wall dynamics
E. Tveten, A. Q., O. Tretiakov, A. Brataas, Phys. Rev. Lett. 110 , 127208 (2013).E. Tveten, A. Q., A. Brataas, Phys. Rev. Lett. 110 , 127208 (2013).
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Ferromagnetic Domain Walls
Neel DW Bloch DW
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FM‐STT: current induced FM-DW motion
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Spin‐transfer torque in magnetic textures : spin-waves induced DW motion
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Racetrack Memory (IBM)
S. Parkin, M. Hayashi, L. Thomas, Science 320, 190 (2008)
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Staggered Dynamics in Antiferromagnets by Collective CoordinatesPhys. Rev. Lett. 110 , 127208 (2013)
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Collective Coordinates Approach
Staggered Dynamics in Antiferromagnets by Collective Coordinates
Magnetic textures are often rigid, so that only a few, soft modes dominate the magnetization dynamics.
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Example: Texture dynamics
Staggered Dynamics in Antiferromagnets by Collective Coordinates
Out‐of‐plane tilt angel and domain wall width are hard modes:
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Anisotropic Magneto‐Resistance (AMR)
Staggered Dynamics in Antiferromagnets by Collective Coordinates
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Antiferromagnetic Domain Wall Motion Induced by Spin Waves
Spin‐wave excitation:
0m
In equilibrium (Walker DW):
00 ,exp )2
,0tan( )(t)(z)(t
w
FM spin‐waves
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Antiferromagnetic Domain Wall Motion Induced by Spin Waves
Dynamical variables:
Linearly polarized magnons:
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Linear polarization
Antiferromagnetic Domain Wall Motion Induced by Spin Waves
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Circular polarization
Antiferromagnetic Domain Wall Motion Induced by Spin Waves
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Antiferromagnetic Domain Wall Motion Induced by Spin Waves
Circularly polarized magnons:
Linearly polarized magnons: 0zmJ
Problem: Magnetic moment cannot constantly increase in an AFM!Result: Spin waves reflect from the domain wall
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Circular polarization
Antiferromagnetic Domain Wall Motion Induced by Spin Waves
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Wadley et al., arxiv1503.03765v1Wadley et al., Nat Comm. 2013
Antiferromagnetic Spin-OrbitronicsSpin‐Orbit Torques in Antiferromagnets
The antiferromagnetic order isControlled by Spin‐orbit TorquesDetected by Anisotropic Magnetoresistance
Bulk inversion asymmetry