07-04-2011, 02:11 PM
Presented by:
VIJAY KASHYAP
[attachment=11851]
spintronics
INTRODUCTION
Spintronics, also known as magnetoelectronics, exploits the intrinsic spin of the electron.
They rely completely on magnetic moment of the electron.
Electrons are spin-1/2 fermions and therefore constitute a two-state system with spin "up" and spin "down".
Electrons have a property that they occupy only one quantum state at a given time.
To make a spintronic device, the primary requirements are a system that can generate a current of spin-polarized electrons comprising more of one spin species—up or down—than the other (called a spin injector),
Spin process can be accomplished using real external magnetic fields or effective fields caused by spin-orbit interaction.
HISTORICAL PERSPECTIVE
The research field of spintronics emerged from experiments on spin-dependent electron transport phenomena in solid-state devices done in the 1980s.
Further in 1997 this technology got a boost by the discovery of Giant magnetoresistance (GMR) .
GMR was discovered by Albert Fert and Peter Grünberg for which they also got nobel prize in physics.
PROPOSED PLASTIC SPINTRONIC MEMORY STICK
WORKING
All spintronic devices act according to the simple scheme:
(1) Information is stored (written) into spins as a particular spin orientation (up or down).
(2) The spins, being attached to mobile electrons, carry the information along a wire, and
(3) The information is read at a terminal.
GIANT MAGNETORESISTANCE(GMR)
GMR is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and non magnetic layers.
In GMR two or more ferromagnetic layers are separated by a very thin (about 1 nm) non-ferromagnetic spacer (e.g. Fe/Cr/Fe). At certain thicknesses the coupling between adjacent ferromagnetic layers becomes
SPIN DETECTION
Spin detection in semiconductors is another challenge, which has been met with the following techniques:
Faraday/Kerr rotation of transmitted/reflected photons.
Circular polarization analysis of electroluminescence.
DEPICTING SPIN OF ELECTRONS
CONCERNS
To devise economic ways to combine ferromagnetic metals and semiconductors in integrated circuits.
To find an efficient way to inject spin-polarized currents, or spin currents, into a semiconductor.
To maximize the time period for spin current to retain its polarization in a semiconductor.
To make semiconductors that are ferromagnetic at room temperature and don’t lose their property even at high temperature
To minimize spin currents at boundaries between different semiconductors so as to minimize the loss .
APPLICATIONS
Motorola has developed a 1st generation 256 kb MRAM based on a single magnetic tunnel junction and a single transistor and which has a read/write cycle of under 50 nanoseconds.
There are two 2nd generation MRAM techniques currently in development:
a).Thermal Assisted Switching (TAS) which is being developed by Crocus Technology, and
b). Spin Torque Transfer (STT) on which Crocus, Hynix, IBM, and several other companies are working.
Semiconductor lasers using spin-polarized electrical injection have shown threshold current reduction and controllable circularly polarized coherent light output.
VIJAY KASHYAP
[attachment=11851]
spintronics
INTRODUCTION
Spintronics, also known as magnetoelectronics, exploits the intrinsic spin of the electron.
They rely completely on magnetic moment of the electron.
Electrons are spin-1/2 fermions and therefore constitute a two-state system with spin "up" and spin "down".
Electrons have a property that they occupy only one quantum state at a given time.
To make a spintronic device, the primary requirements are a system that can generate a current of spin-polarized electrons comprising more of one spin species—up or down—than the other (called a spin injector),
Spin process can be accomplished using real external magnetic fields or effective fields caused by spin-orbit interaction.
HISTORICAL PERSPECTIVE
The research field of spintronics emerged from experiments on spin-dependent electron transport phenomena in solid-state devices done in the 1980s.
Further in 1997 this technology got a boost by the discovery of Giant magnetoresistance (GMR) .
GMR was discovered by Albert Fert and Peter Grünberg for which they also got nobel prize in physics.
PROPOSED PLASTIC SPINTRONIC MEMORY STICK
WORKING
All spintronic devices act according to the simple scheme:
(1) Information is stored (written) into spins as a particular spin orientation (up or down).
(2) The spins, being attached to mobile electrons, carry the information along a wire, and
(3) The information is read at a terminal.
GIANT MAGNETORESISTANCE(GMR)
GMR is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and non magnetic layers.
In GMR two or more ferromagnetic layers are separated by a very thin (about 1 nm) non-ferromagnetic spacer (e.g. Fe/Cr/Fe). At certain thicknesses the coupling between adjacent ferromagnetic layers becomes
SPIN DETECTION
Spin detection in semiconductors is another challenge, which has been met with the following techniques:
Faraday/Kerr rotation of transmitted/reflected photons.
Circular polarization analysis of electroluminescence.
DEPICTING SPIN OF ELECTRONS
CONCERNS
To devise economic ways to combine ferromagnetic metals and semiconductors in integrated circuits.
To find an efficient way to inject spin-polarized currents, or spin currents, into a semiconductor.
To maximize the time period for spin current to retain its polarization in a semiconductor.
To make semiconductors that are ferromagnetic at room temperature and don’t lose their property even at high temperature
To minimize spin currents at boundaries between different semiconductors so as to minimize the loss .
APPLICATIONS
Motorola has developed a 1st generation 256 kb MRAM based on a single magnetic tunnel junction and a single transistor and which has a read/write cycle of under 50 nanoseconds.
There are two 2nd generation MRAM techniques currently in development:
a).Thermal Assisted Switching (TAS) which is being developed by Crocus Technology, and
b). Spin Torque Transfer (STT) on which Crocus, Hynix, IBM, and several other companies are working.
Semiconductor lasers using spin-polarized electrical injection have shown threshold current reduction and controllable circularly polarized coherent light output.
