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AMR and GMR (TMR) sensors: dawn of spintronics Inductive read elements Magnetoresistive read elements 1980’s-1990’s
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Institute of Physics ASCR Hitachi Cambridge, Univ.
Cambridge
From ferromagnetic to non-magnetic semiconductor spintronics:
Spin-injection Hall effect Tomas Jungwirth University of Nottingham
Bryan Gallagher, Richard Campion, Kevin Edmonds, Andrew Rushforth,
et al. Institute of Physics ASCR Karel Vborn, Jan Zemen, Jan Maek,
Vt Novk, Kamil Olejnk, et al. Hitachi Cambridge, Univ. Cambridge
Jorg Wunderlich, Andrew Irvine, Byonguk Park,et al. Texas A&M
Jairo Sinova, et al. AMR and GMR (TMR) sensors: dawn of
spintronics
Inductive read elements Magnetoresistive read elements 1980s-1990s
Ferromagnetism & spin-orbit coupling anisotropic
magnetoresistance
Ferromagnetismonly giant (tunnel) magnetoresistance ~ 100% MR
effect ~ 1% MR effect magnetization current Lord Kelvin 1857 Fert,
Grunberg et al. 1988 Renewed interest in SO induced MRs in
ferromagnetic semiconductors
~ 1000% MR effect & gate controlled Ohno Science 98 Coulomb
blockade AMR: likely the most sensitive spintronic transistors to
date Wunderlich et al. PRL 06 Coulomb blockade oscillations in
(Ga,MnAs) SET as a function of gate voltage and magnetization angle
Schlapps et al. arXiv: I B M I V V SO induced MRs: AMR &
anomalous Hall effect _ _ _
Ordinary Hall effect: response in normal metals to external
magnetic field via classical Lorentz force Anomalous Hal effect:
response to internal spin polarization in ferromagnets via
quantum-relativistic spin-orbit coupling B Hall 1879 Hall 1881 V _
M _ _ FSO _ FL I I V Tc in (Ga,Mn)As upto ~190 K but AHE survives
and dominates above room-T Ruzmetov et al. PRB 04 (Ga,Mn)As: simple
band structure of the host SC
j=3/2 HH HH & LH Fermi surfaces Spherical HH Kohn-Luttinger 3D
model Rashba and Dresselhaus 2D models Intense theory research of
AHE in model 2D R&D systems
Nagaosa et al RMP 09 in press (arXiv: ) Spin-injection Hall effect:
SO-induced Hall effect of spin-polarized electrical current
injected into non-magnetic system (2DEG) jqs nonmagnetic
Spin-polarizer (e.g. ferromagnet, light) Wunderlich et al. Nature
Phys.09 - spintronic effect in non-magnetic semiconductors based on
SO only immediate prospect for high-T operation - SO-induced Hall
effect (like AHE) in the model 2D Rashba&Dresselhaus systems -
and more . - spin-detection tool of unique SO-induced spin dynamics
effects in 2D systems - directly applicable to a variety of
opto-spintronic, spintronic transitor, etc. devices Optical
injection of spin-polarized charge currents into Hall bars
GaAs/AlGaAs planar 2DEG-2DHG photovoltaic cell p 2DHG i n 9 Optical
injection of spin-polarized charge currents into Hall bars
GaAs/AlGaAs planar 2DEG-2DHG photovoltaic cell - p 2DHG i n 10
Optical injection of spin-polarized charge currents into Hall
bars
GaAs/AlGaAs planar 2DEG-2DHG photovoltaic cell i p n 2DHG 2DEG 11
Optical injection of spin-polarized charge currents into Hall
bars
GaAs/AlGaAs planar 2DEG-2DHG photovoltaic cell h h h h h h VH e e e
e e e 2DHG 2DEG Optical spin-generation area near the p-n
junction
Simulated band-profile p-n junction bulit-in potential (depletion
length ) ~ 100 nm self-focusing of the generation area of
counter-propagating e- and h+ Hall probes further than 1m from the
p-n junction safely outside the spin-generation area and/or masked
Hall probes Experimental observation of the SIHE SIHE linear in
degree of polarization and spatially varying Spin dynamics in
Rashba&Dresselhaus SO-couped 2DEG
> 0, = 0 = 0, < 0 k-dependent SO field strong precession
& spin-decoherence due to scattering No decoherence for || = ||
& channel SO field
Bernevig et al PRL06 [110] [1-10] Diffusive spin dynamics &
Hall effect due to skew scattering
18 lacks nano-scale resolution
SIHE vs other spin-detection tools in semiconductors
Magneto-optical imaging non-destructive lacks nano-scale resolution
and only an optical lab tool Crooker et al. JAP07, others MR
Ferromagnet electrical requires semiconductor/magnet hybrid design
& B-field to orient the FM Ohno et al. Nature99, others
spin-LED all-semiconductor requiresfurther conversion of emitted
light to electrical signal 100-10nm resolution with current
lithography
Spin-injection Hall effect non-destructive electrical nm resolution
with current lithography in situ directly along the SC channel
& all-SC requiring no magnetic elements in the structure or
B-field Conclusions SIHE: high-T SO only spintronics in
non-magnetic systems Basic studies of spin-charge dynamics and Hall
effect in non-magnetic systems with SO coupling Spin-photovoltaic
cell: polarimeter on a SC chip requiring no magnetic elements,
external magnetic field, or bias All-electric Datta-Das like
transistor with Fe or (Ga,Mn)As spin-injectors, top/bottom gate
electrode, and SIHE detection