Tuesday, March 2, 2010

Spin Valve Transistor

In our conventional electronic devices we use semi conducting materials for logical operation and magnetic materials for storage, but spintronics uses magnetic material for both purposes. These spintronics devices are more versatile and faster than in the present one. One such device is spin valve transistor.Spin valve transistor is different from conventional transistor. In this for conduction we use spin polarization of electrons. Only electrons with correct spin polarization can travel successfully through the device. These transistors are used in data storage, signal processing, automation and robotics with less power consumption and results in less heat. This also finds its application in Quantum computing in which we use Qubits instead of bits.Spin is the root cause of magnetism that makes an electron a tiny magnet. Magnetism is already been exploited in recording devices.Where data is recorded and stored as tiny areas of magnetized iron or chromium oxide. To access that information the head detects the minute changes in magnetic fields. This induces corresponding changes in the head’s electrical resistance-a phenomenon called Magneto Resistance.
Spintronics came into light by the advent of Giant Magneto Resistance(GMR).GMR is much stronger than ordinary Magneto Resistance .It results from subtle electron – spin effects in ultra multilayers of magnetic materials that cause a huge change in electrical resistance.Giant Magneto Resistance is the phenomenon where the resistance of certain materials drops dramatically as a magnetic field is applied.It is described as Giant since it is a much larger effect than had ever been previously seen .The effect is most usually seen in magnetic multilayered structures, where two magnetic layers are closely separated by a thin spacer layer a few nm thick. For preparation of transistors we apply vaccum bonding both to obtain device quality semi conductor material for emitter and to allow room temperature processes.

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