Spin Torque Transfer
Encyclopedia
Spin-transfer torque is an effect in which the orientation of a magnetic layer in a tunnel magnetoresistance or spin valve
can be modified using a spin-polarized current.
Charge carriers (such as electrons) have a property known as spin
which is a small quantity of angular momentum
intrinsic to the carrier. An electrical current is generally unpolarized (consisting of 50% spin-up and 50% spin-down electrons); a spin polarized current is one with more electrons of either spin. By passing a current through a thick magnetic layer, one can produce a spin-polarized current. If a spin-polarized current is directed into a magnetic layer, angular momentum can be transferred to the layer, changing its orientation. This can be used to excite oscillations
or even flip the orientation of the magnet. The effects are usually only seen in nanometer scale devices.
Hynix Semiconductor and Grandis formed a partnership in April 2008 to explore commercial development of STT-RAM technology. On August 1, 2011, Grandis announced that it had been purchased by Samsung for an undisclosed sum.
Hitachi and Tohoku University demonstrated a 32-Mbit STT-RAM in June 2009.
Other companies working on STT-RAM include Crocus Technology and Spin Transfer Technologies. In May 2011, Russian Nanotechnology Corp. announced an investment of $300 millions in Crocus Technology which will build an MRAM factory in Russia.
Spin valve
A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance depending on the alignment of the magnetic layers, in order to exploit the Giant Magnetoresistive effect. The magnetic layers of the device align "up" or "down" depending on...
can be modified using a spin-polarized current.
Charge carriers (such as electrons) have a property known as spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
which is a small quantity of angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
intrinsic to the carrier. An electrical current is generally unpolarized (consisting of 50% spin-up and 50% spin-down electrons); a spin polarized current is one with more electrons of either spin. By passing a current through a thick magnetic layer, one can produce a spin-polarized current. If a spin-polarized current is directed into a magnetic layer, angular momentum can be transferred to the layer, changing its orientation. This can be used to excite oscillations
Ferromagnetic resonance
Ferromagnetic resonance, or FMR, is a spectroscopic technique to probe the magnetization of ferromagnetic materials. It is a standard tool for probing spin waves and spin dynamics...
or even flip the orientation of the magnet. The effects are usually only seen in nanometer scale devices.
Spin-transfer torque memory
Spin-transfer torque can be used to flip the active elements in magnetic random access memory. Spin-transfer torque random access memory, or STT-RAM, has the advantages of lower power consumption and better scalability over conventional MRAM which uses magnetic fields to flip the active elements. The name STT-RAM was first coined by Grandis, Inc. Spin-transfer torque technology has the potential to make possible MRAM devices combining low current requirements and reduced cost; however, the amount of current needed to reorient the magnetization is at present too high for most commercial applications, and the reduction of this current density alone is the basis for current academic research in spin electronics.Hynix Semiconductor and Grandis formed a partnership in April 2008 to explore commercial development of STT-RAM technology. On August 1, 2011, Grandis announced that it had been purchased by Samsung for an undisclosed sum.
Hitachi and Tohoku University demonstrated a 32-Mbit STT-RAM in June 2009.
Other companies working on STT-RAM include Crocus Technology and Spin Transfer Technologies. In May 2011, Russian Nanotechnology Corp. announced an investment of $300 millions in Crocus Technology which will build an MRAM factory in Russia.
See also
- Magnetoresistive Random Access Memory (MRAM)MRAMMagnetoresistive Random-Access Memory is a non-volatile computer memory technology that has been under development since the 1990s. Continued increases in density of existing memory technologies – notably flash RAM and DRAM – kept it in a niche role in the market, but its proponents...
- Spin (physics)Spin (physics)In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
- Memresistor
- SpintronicsSpintronicsSpintronics , also known as magnetoelectronics, is an emerging technology that exploits both the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-state devices.An additional effect occurs when a spin-polarized current is...
External links
- Spin torque applet
- Solicitation Number: BAA08-16 from the Defense Advanced Research Projects Agency
- J.C. Slonczewski:"Current-driven excitation of magnetic multilayers(1996)", Journal of Magnetism and Magnetic Materials Volume 159, Issues 1-2, June 1996, Pages L1-L7
- Crocus technology