The simplest method of

							                                           ‫اسپین ترونیک‬

                                         (Spintronics)


 ‫از اسپین الکترون ها در الکترونیک است. در اسپینترونیک علم استفاده الکترونیک اسپینی اسپینترونیک یا‬
    ‫به جای "صفر و یک" یا "مثبت و منفی" استفاده میشود و در آینده تحولی در حالت "باال و پایین" اسپینی‬
     ‫میکروالکترونیکی بوجود خواهد آورد. این ویژگی برای ساخت دستگاه های باینری بسیار دستگاه های‬
            ‫.داشت کوچک، یعنی در مقیاس اتمی، مورد استفاده قرار میگیرد که انرژی کمتری الزم خواهند‬




 ‫در حاالت بینابین نیز وجود به عالوه از طبیعت کوانتومی چنین برمیآید که اسپین غیر از باال و پایین میتواند‬
                                                   ‫داشته باشد و با استفاده از این خاصیت در پردازش موازی‬

                                                                          (parallel computation)

                                      ‫سرعت باالتری برای کامپیوتر های کوانتومی در دسترس خواهد بود‬




[edit] Theory
In order to make a spintronic device, the primary requirement is to have a system that
can generate a current of spin polarised electrons, and a system that is sensitive to the
spin polarization of the electrons. Most devices also have a unit in between that
changes the current of electrons depending on the spin states.

The simplest method of generating a spin polarised current is to inject the current
through a ferromagnetic material. The most common application of this effect is a
giant magnetoresistance (GMR) device. A typical GMR device consists of at least two
layers of ferromagnetic materials separated by a spacer layer. When the two
magnetization vectors of the ferromagnetic layers are aligned, then an electrical
current will flow freely, whereas if the magnetization vectors are antiparrallel then the
resistance of the system is higher. Two variants of GMR have been applied in devices,
current-in-plane where the electric current flows parallel to the layers and current-
perpendicular-to-the-plane where the electric current flows in a direction
perpendicular to the layers.

[edit] Applications
Spintronic devices are used in the field of mass-storage devices; recently (in 2002)
IBM scientists announced that they could compress massive amounts of data into a
small area, at approximately one trillion bits per square inch (1.5 Gbit/mm²‫ )آ‬or
roughly 1 TB on a single sided 3.5" diameter disc. The storage density of hard drives
is rapidly increasing along an exponential growth curve. The doubling period for the
areal density of information storage is twelve months, much shorter than Moore's
Law, which observes that the number of transistors in an integrated circuit doubles
every eighteen months. Also the hard disk drives use a spin effect to function, the
Giant magnetoresistive effect (see below).

The most successful spintronic device to date is the spin valve. This device utilizes a
layered structure of thin films of magnetic materials, which changes electrical
resistance depending on applied magnetic field direction. In a spin valve, one of the
ferromagnetic layers is "pinned" so its magnetization direction remains fixed and the
other ferromagnetic layer is "free" to rotate with the application of a magnetic field.
When the magnetic field aligns the free layer and the pinned layer magnetization
vectors, the electrical resistance of the device is at its minimum. When the magnetic
field causes the free layer magnetization vector to rotate in a direction antiparallel to
the pinned layer magnetization vector, the electrical resistance of the device increases
due to spin dependent scattering. The magnitude of the change, (Antiparallel
Resistance - Parallel Resistance) / Parallel Resistance x 100% is called the GMR ratio.
Devices have been demonstrated with GMR ratios as high as 200% with typical
values greater than 10%. This is a vast improvement over the anisotropic
magnetoresistance effect in single layer materials which is usually less than 3%. Spin
valves can be designed with magnetically soft free layers which have a sensitive
response to very weak fields (such as those originating from tiny magnetic bits on a
computer disk), and have replaced anisotropic magnetoresistance sensors in computer
hard disk drive heads since the late 1990s.

Future applications may include a spin-based transistor which requires the
development of magnetic semiconductors exhibiting room temperature
ferromagnetism. The operation of MRAM or magnetic random access memory is also
based on spintronic principles.




Spintronics
Feature: April 2002

Devices that exploit the spin of the electron promise to revolutionize
microelectronics once polarized electrons can be injected efficiently into
semiconductors at room temperature.
Later this year physicists will be celebrating the centenary of Paul Dirac's birth. One of the
most influential scientists of the 20th century, Dirac combined quantum mechanics and
special relativity to explain the strange magnetic or "spin" properties of the electron. What
Dirac could not have foreseen, however, is how the spin of the electron could change the
field of microelectronics.
Indeed, the spin of the electron has attracted renewed interest recently because it
promises a wide variety of new devices that combine logic, storage and sensor
applications. Moreover, these "spintronic" devices might lead to quantum computers and
quantum communication based on electronic solid-state devices, thus changing the
perspective of information technology in the 21st century.
Since the 1970s conventional electronic microprocessors have operated by shuttling
packets of electronic charge along ever-smaller semiconductor channels. Although this
trend will continue for the next few years, experts predict that silicon technology is
beginning to approach fundamental limits. By 2008, for example, the width of the "gate
electrodes" in a silicon microprocessor will be just 45 nanometres across, which will place
severe demands on the materials and manufacturing techniques used in the semiconductor
industry. Indeed, the cost of implementing a new production line for such devices is
predicted to reach $33bn.
Although successors to silicon technology have been discussed, most of them rely on a
complete set of new materials, new handling and processing techniques, and altered circuit
design, among other developments. These new technologies include single-electron
transistors and molecular-electronic devices based on organic materials or carbon
nanotubes (see Carbon nanotubes roll on Physics World June 2000 pp31-36).
But the ability to exploit the spin degree of freedom in semiconductors promises new logic
devices with enhanced functionality, higher speeds and reduced power consumption.
Crucially, these devices could be fabricated with many of the tools already used in the
electronics industry, thereby speeding up their development. The challenge for
manufacturers is to combine the technology in the semiconductor industry with the
completely different techniques used in the magnetic-recording industry to produce
devices on the nanometre scale.
In the April issue of Physics World, Dirk Grundler of the University of Hamburg describes
how the recent developments in spin transport and spin injection may herald a new era of
semiconductor spintronics that could potentially transform the microelectronics industry.




                                                                     ) ‫اسپین ترونیک چیست؟ :( زهرا‬

 ، ‫اسپینترونیک یا الکترونیک اسپینی علم استفاده از اسپین الکترون ها در الکترونیک است. اسپین الکترونها‬
‫چگونگي حرکت الکترون بدور هسته می باشد و از این بابت اسپین نامیده مي شود که این حرکت را مارپیچي‬
                  .‫فرض نموده و حضور الکترون را در هر نقطه در هر لحظه ؛ احتمالي در نظر گرفته اند‬

  ‫در اسپینترونیک؛ حالت "باال و پایین" اسپینی به جای "صفر و یک" یا "مثبت و منفی" استفاده میشود و در‬
     ‫آینده تحولی در دستگاه های میکروالکترونیکی بوجود خواهد آورد. این ویژگی برای ساخت دستگاه های‬
.‫باینری بسیار کوچک، یعنی در مقیاس اتمی، مورد استفاده قرار میگیرد که انرژی کمتری الزم خواهند داشت‬

 ‫به عالوه از طبیعت کوانتومی چنین برمیآید که اسپین غیر از باال و پایین میتواند در حاالت بینابین نیز وجود‬
‫) سرعت باالتری برای‬parallel computation( ‫داشته باشد و با استفاده از این خاصیت در پردازش موازی‬
                                                           .‫کامپیوتر های کوانتومی در دسترس خواهد بود‬
                                          :‫به این سایت هم سر بزن‬
            http://unit.aist.go.jp/nano-ele/spinics/index.htm

                     http://www.wisegeek.com/what-is-spintronics.htm

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