Circular Polarizing Filter

Circular Polarizing Filter

Spintronics in Computer

Spintronics computer

Spintronics is an emerging technology that exploits the intrinsic properties of the electron spin and magnetic moment associated.

In 1980 the experiments on the transport phenomena dependent of electron spin in solid state devices donerevealed field of research includes the observation spintronics.It injection of electrons spin polarized ferromagnetic metal to a normal metal.

The electrons are spin-1 / 2 fermions. Fermion constitute a system of two states with spin "up" and spin "down." A current of spin-polarized electrons with more than one spin-species up or down, is the main requirement for spintronic devices. Therefore, turn devices require injectors and a separate system that is sensitive to spin polarization of electrons (spin detector). Manipulation of electron spin during transport between the injector and detector (especially in semiconductors) through spin precession is can be accomplished using external magnetic fields or effective field caused by spin-orbit interaction

Spin pol arization non-magnetic materials can achieved either through the Zeeman effect in large magnetic fields and low temperatures, or non-equilibrium methods. In the latter case, the polarization of nonequilibrium disintegrate in a period of time called the lifetime "twist." Spin lives of conduction electrons in metals are relatively short (<1nsec) but in semiconductors the lifetimes can be very long (μsec at low temperatures), especially when electrons are trapped in local trapping potential.

style = "text-decoration: underline;"> Metals spintronic-based devices

The method simple to generate a spin-polarized in a metal is to pass the current through a ferromagnetic material. This effect is useful in a giant magnetoresistance (GMR) device. A GMR device consists of at least two ferromagnetic material layers separated by a spacer layer. When the two magnetization vectors of ferromagnetic layers are aligned, the electrical resistance is lower (so a higher current flow to the constant voltage) that if the ferromagnetic layers are anti-aligned. This is a magnetic field sensor.ie device acts as an investor can, with the logic 0 or logic1.

Two variants have been applied in GMR devices:

(1) currently on the plane (CIP), where the electrical current flow parallel to the layers and

(2) current perpendicular to plane (CPP), where electric current flows in a direction perpendicular to the layers.

Other metal-based spintronic devices:

  1. Tunnel magnetoresistance (TMR): In this device the CPP transport is achieved through the use of quantum mechanical tunneling of electrons through a thin insulating layer separating the ferromagnetic.
  2. Return transfer torque: This a stream of spin-polarized electrons is used to control the direction of magnetization of the electrodes ferromagnetic device.

Semiconductor-based devices of spintronics

The spin-polarized electrons are generated through optical orientation using circularly-polarized photons in the incident bandgap energy of semiconductors with spin-orbit interaction sensitive (such as GaAs and ZnSe). While electrical spin injection can be achieved in metallic systems simply by passing a current through a ferromagnet, the lack of agreement between ferromagnetic metals and semiconductors large injection prevented efficient in all the metal semiconductor interfaces. One solution to this problem is to use ferromagnetic semiconductor sources (such as manganese arsenide gallium doped GaMnAs) increasing the strength of interface with a tunnel barrier, or the use of hot electron injection.

Spin detection in semiconductors is another challenge has been met with the following techniques:

  1. Faraday / Kerr rotation transmitted / reflected photons
  2. Circular analysis electroluminescence polarization
  3. nonlocal spin valve (adapted from Johnson and Silsbee metalworking
  4. Ballistic spin filtering

The latter technique is used to overcome the lack of spin-orbit interaction and issues materials to achieve spin transport in silicon, the most important semiconductor for electronics.

For external magnetic fields can cause large Hall effect and magnetoresistance in semiconductors, the only conclusive evidence of spin transport in semiconductors is the demonstration of precession and rotation gap in a magnetic field aligned the injected spin orientation. This is known as the Hanle effect.

Device Applications spintronics

  1. The storage density of hard drives is increasing rapidly along an exponential growth curve, in part because Spintronics-enabled devices such as GMR sensors and IMF have increased the sensitivity of the read head to measure the magnetic state of tiny magnetic domains (Bits) on the turntable. The deadline for the doubling of the density areas of information storage is twelve months, much shorter than Moore's Law, which notes that the number of transistors and cheaper than can be incorporated into an integrated circuit doubles every two years.
  2. Racetrack memory
  1. MRAM, or magnetic random access memory, uses a grid of magnetic storage elements called magnetic tunnel junctions (MTJ's). MRAM is nonvolatile way information is stored even when power is off, you can provide instant-on computing. Motorola has developed a 1st generation MRAM 256 kb based on individual magnetic tunnel junction and a single transistor and has a read / write cycle of less than 50 nanoseconds.

by heart Racetrack, encodes information in the direction of magnetization between

domain walls of ferromagnetic metal wire.

4.Advantages of semiconductor-based spintronics applications are potentially use less fuel and a smaller footprint that the electrical devices used to process information In addition, applications such as semiconductor lasers using electrical injection of spin polarized demonstrated reduction current threshold and controllable circularly polarized coherent light output. Future applications may include a spin-based devices with advantages over the MOSFET as steep hillside below the threshold.

References

IBM RD 50-1 ^ | Spintronics-A retrospective and perspective

^ Profile of Physics: Stu Wolf: True Q! History of Hollywood "

^ Http://prola.aps.org/pdf/PRL/v55/i17/p1790_1

^ Phys. Rev. Lett. 61 (1988): Baibich MN, JM Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, G. Creuzet, A. Friederich, and J. Chazel – Giant Magnetoresistanc …

^ Http: / / prola.aps.org/pdf/PRB/v39/i7/p4828_1

^ PII: 0370-1573 (94) 90105-8

^ Http: / / www.sciencedirect.com/science/article/B6TVM-46R3N46-10D/2/90703cfc684b0679356dce9a76b2e942

^ Requires cookies

^ Http: / / www.sigmaaldrich.com / materials-science / alternative-energy-materials / magnetic-materials / tutorial / spintronics.html

^ Http://www.everspin.com/technology.html

^ The development of MRAM practices http://www.crocus-technology.com/pdf/BH GSA article.pdf

^ Http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=218000269

^ Phys. Rev. B 62 (2000): BT Jonker, YD Park, BR Bennett, HD Cheong, G. Kioseoglou and A. Petrou – Electrical spin injection robust

Cookies ^ Requested

^ Phys. Rev. Lett. 90 (2003): X. Jiang, R. Wang, S. Van Dijken, R. Shelby, R. Macfarlane, GS Solomon, J. Harris, and SS Parkin – Optical detection of Hot-Electron

^ Phys. Rev. Lett. 80 (1998): JM Kikkawa and DD Awschalom – Spin resonant amplification

^ Optics polarized emissions from the decomposition or recombination of spin-polarized injected carriers – U.S. Patent 5874749

^ Electrical detection of spin transport in lateral ferromagnet-semiconductor devices: Abstract: Nature Physics

^ Electronic measurement and control of spin transport in silicon: Abstract: Nature

^ Availability: Nature

^ Access:: Nature

^ Cookies Required

Also read

"Introduction to spintronics." Cahaya Marc, Supriya Bandyopadhyay, CRC Press, ISBN 0-8493-3133-1

Ultrafast electron Handling Spin coherence. JA Garcia, R. Knobel, N. Samarth and DD Awschalom in Science, vol. 292, pages 2458-2461, June 29, 2001.

Spintronics: a spin-base Electronics Vision for the Future. SA Wolf et al., Science 294, 1488-1495 (2001)

How to create a current spin. P. Sharma, Science 307, 531-533 (2005)

Search Google Scholar for heavily cited query: spintronics O magnetoelectronics O "spin-based electronics"

"Electron Spin Manipulation and" current. D. Grinevich. 3rd edition, 2003 .*

Semiconductor spintronics. Fabián J., A. Matos-Abiague, C. Ertler, P. Stano and Žutić I., Phys Minutes Slovaca 57, 565-907 (2007)

Spintronics: Fundamentals and Applications. I. Žutić, J. Fabian and S. Das Sarma, Rev. Mod. Phys. 76, 323-410 (2004)

External Links

"Spintronics". Scientific American. June 2002. http://www.sciam.com/article.cfm?articleID=0007A735-759A-1CDD-B4A8809EC588EEDF.

Course: InformationWeek (April 11, 2008)

IBM (2003)

Wired: update on MRAM, July 2003

Spintronics GaAs research objectives.

Spintronics at the Indian Institute of Science, Bangalore, India

Spintronics SUNY Albany at the College of Science Nanoscale and Engineering

Spintronics information community site

IBM to use 'spintronics' to increase capacity computer memory (April 12, 2008)

Semiconductor Spintronics Laboratory at the University of Maryland

Spintronics Tutorial

Tanveer Rabiya.

LECTURER IN PHYSICS

Chaitanya and PG COLLEGE DEGREE

HNK, Warangal, INDIA.

AFFILIATION:

1.NANO Science and Technology Consortium,

Noida, UP.INDIA.

2.PHOTONICS 21 European Technology Platform. EMAIL: munaizag@gmail.com

About the Author

Lecturer

Dept. of physics & electronics,

 Chaitanya degree & P.G  College, kishan pura ,hanamkonda, warangal.A.P,india.

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