Dilute moment ferromagnetic semicinductors for spintronics

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Dilute moment ferromagnetic semicinductors for
spintronics
Tomas Jungwirth
Bryan Gallagher, Tom Foxon, Richard Campion,
Kevin Edmonds, Andrew Rushforth, Devin
Giddings, Chris King, et al.
Jan Mašek, Alexander Shick Karel Výborný,
Jan Zemen, Vít Novák, et al.
Prague
Nottingham
NANOSPIN
Jorg Wunderlich, David Williams, Andrew Irvine,
Kaiyou Wang, Elisa De Ranieri, et al.
CNRS, Wuezburg, Warsaw, Thales
Texas Universities Jairo Sinova, Allan H.
MacDonald. et al.
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(Ga,Mn)As (and realated DMSs)
spintronics Ideal systems for exploring basic
physics and new functionality concepts
Dilute moment ferromagnets based on semiconductor
material dependence on doping low saturation
magnetization
Ferromagnetic Mn-Mn coupling mediated by GaAs
host-like As p-orbital band states strongly
exchange split and SO coupled yet relatively
simple carrier bands
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Spintronics based on extraordinary
magnetoresistance effects (AHE, AMR, STT,TMR,....)
Extraordinary magnetoresistance response to
internal magnetization in ferromagnets often via
quantum-relativistic spin-orbit coupling
anisotropic magnetoresistance
For decades controversial in conventional metal
FMs model of (non-SO-coupled non-exchange-split)
s-state carriers and localized d-states ?
difficult to match with microscopic bands of
mixed s-d character
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Origin of AMR
Basic symmetry arguments for zincblende DMSs
(GaMnAs)
SO-coupling spherical model
FM exchange spiitting
scattering rate
(k . s)2
Mx . sx
hot spots for scattering of states moving ? M ?
R(M ? I)gt R(M I)
Successful microscopic modelling
AMRtheor.
AMRexp.
still R(M ? I)gt R(M I) plus magnetocrystalline
anisotropy corrections (M vs. crystal axes)
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A family of new AMR effects dicovered in GaMnAs
- TAMR sensor/memory elemets
TAMR
TMR
no need for exchange biasing or spin coherent
tunneling
Au
predicted and recently confirmed to exist in
conventional metal FMs

• - CBAMR spintronic transistor
• combining processing with
• permanent storage and p-type
• and n-type transistor characteristics

predicted to exists in conventional metal FMs
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Spintronic transistor based on CBAMR
Huge, gatable, and hysteretic MR
Single-electron transistor
Two "gates" electric and magnetic
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Spintronic transistor based on CBAMR
magnetic
electric
control of Coulomb blockade oscillations
? magnitude of MR reaches magnitude of CB
oscillations
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Strong spin-orbit coupling ? band structure
depends on M ? chemical potential depends on M

• CBAMR if change of ??(M) e2/2C?
• In (Ga,Mn)As meV ( 10 Kelvin)
• In room-T ferromagnet change
• of ??(M)100K

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CBAMR SET

• Generic effect in FMs with SO-coupling
• 10 K in GaMnAs, 100 K in room-Tc metal FM
• Combines electrical transistor action
• with magnetic storage
• Switching between p-type and n-type transistor
  
• by M ? programmable logic

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(Ga,Mn)As (and realated DMSs)
spintronics Ideal systems for exploring basic
physics and new functionality concepts
Dilute moment ferromagnets based on semiconductor
material dependence on doping low saturation
magnetization
Ferromagnetic Mn-Mn coupling mediated by GaAs
host-like As p-orbital band states strongly
exchange split and SO coupled yet relatively
simple carrier bands
unprecedented micromagnetics ? Jorg Wunderlich's
talk