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Physics and applications ofPhysics and applications of spintronicsspintronics
Tomas Jungwirth
University of NottinghamInstitute of Physics ASCR, Prague
University of Cambridge & Hitachi Cambridge Lab
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Information reading
Information reading & storage
MRAM chips
Information reading & storage & writing
magnetization switching by spin-currents
Information reading & storage & writing & processingspins & transistors & semiconductors
Mn
Ga
As Mn
Spintronics explores new avenues for
GMR, TMR sensors
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quantum mechanics & special relativity
Spin from relativistic quantum mechanicsSpin from relativistic quantum mechanics
Dirac equation electron has charge and internal angular momentum
internal magnetic moment = spin
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SpintronicsSpintronics
its all about spin and charge of electroncommunicating with each other
ee-- ss
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FerromagnetismFerromagnetism == PauliPauli exclusion principle & Coulomb repulsionexclusion principle & Coulomb repulsion
DOS
DOS
ee--
ee--
ee--
Collective spin behavior easy to manipulate spins large sensitivity (magnetic fields)
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SpinSpin--orbit couplingorbit coupling
nucleus rest frame electron rest frame
EvSBS == 222 mc
eg
HB
SOh
ee--
Magnetic anisotropy bistability & hysteresis magnetic memory
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Simplicity of translation fromphysics to electronics
Resistor
Tunneling device
Electro-chemical potential
Density of states
Scattering lifetimes
Complexity of designEfficiency ofEfficiency of
spintronicspintronic devicesdevices
Single Electron Transistor
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~ 100% MR effect~ 100% MR effect
DOS < DOS
SpinSpin--dependent DOSdependent DOS tunnelingtunneling magnetoresistancemagnetoresistance
DOS < DOS
DOS < DOS
DOS > DOS >
HDD read-head sensors
Non-volatile magnetic RAM
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M
[110]
[100]
[110] [010]
SpinSpin--dependent electrodependent electro--chemical potentialchemical potential
M
M
~1000% MR controlled by low-gate-voltage
spintronicspintronic transistortransistor for amplification and logic
Source Drain
Gate
VG
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WhyWhy spintronicspintronic transistors?transistors?
IntergratingIntergrating conventionalconventional spintronicspintronic and electronic devices in one physical elementand electronic devices in one physical elemente.g. TMR magnetic tunnel junctions with transistorse.g. TMR magnetic tunnel junctions with transistors
Pure electrical control (no external magnetic fields) ofPure electrical control (no external magnetic fields) of spintronicsspintronics
e.g. magnetization switching induced by gate voltage on ae.g. magnetization switching induced by gate voltage on a spintronicspintronic transistortransistor
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Mn
Ga
As
Mn
Other approach: make conventional SC magneticOther approach: make conventional SC magnetic
GaAsGaAs -- standard IIIstandard III--V semiconductorV semiconductor
GroupGroup--IIII MnMn -- dilutedilute magneticmagnetic momentsmoments
& holes& holes
GaAsGaAs::MnMn -- feferrromagneticromagnetic & electrically& electricallydoped semiconductordoped semiconductor
More tricky than just hammering an iron nail in a silicon wafer
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Non-volatile gating of GaAs:Mn by ferroelectric gate
superhybrid ferromagnetic/ferroelectric/semiconducting FET
Electrical gate control of ultra-thin Fe on Au
large change of magnetic anisotropy byelectric fields in room-temperature FM
Proximity effects in FS/FM hybrids
magnetic behavior of a GaAs:Mninterfacial layer at room-temperature
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I || E
_ FSO
FSO
_ __
Spin Hall effect
spin-dependent deflection transverse edge spin polarization
E
+v
-v
+S
-S
EvS =2
mc
eHSO
SpintronicsSpintronics in nonin non--magnetic materialsmagnetic materials
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spin Hall effect mikro-chip
Same magnetization in a normal semiconductor achieved at106 x smaller dimensions & 106 x smaller currents
superconducting magnet
The potential ofThe potential of spintronicsspintronics ..
need to learn much more to fully exploit spin in microelectronneed to learn much more to fully exploit spin in microelectronicsics
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