Published : 01-01-2015 by : Pawan Janorkar

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In the weird world of quantum mechanics the fundamental, particle, electron possesses a property Called ‘spin’. It is not the sort of spin used in common everyday speech but, the angular momentum or the rotational momentum of a subatomic particle that creates its own tiny magnetic field. By exploiting this spin property, in a field called spintronics, computer scientists and physicists have the potential to revolutionise the basis of computer processing and storage technologies.

‘Spintronics’ can be a fairly new term for you but the concept isn’t so very exotic this technological discipline aims to exploit the subtle and mind-bending esoteric quantum properties of the electron to develop a new generation of electronic devices. The word itself is a blend of electronics with spin, the quantum property it exploits. Like so many words applied to the subatomic realm, you can refer spin figuratively as a convenient label for a property that has no equivalent in gross matter.

Every electron exists in one of two states, namely, spin-up and spin-down, with its spin either +1/2 or - 1/2 (refer Figs 1 and 2). In other words, an electron can rotate either clockwise or anticlockwise around its own axis with constant frequency. The two possible spin states naturally represent ‘0’ and ‘1’ states in logical operations. And just because of this it is possible to make a sandwich of gold atoms between two thin films of magnetic material that acts as, a filter or a valve permitting only the electrons in one of the two states to pass. 

Semiconductor spintronics devices combine advantages of semiconductor with the concept of magnetoelectronics. This category of devices includes spin diodes, spin filter, and spin FET. To make semiconductor based spintronic devices, researchers need to address several following different problems. A first problem is creation of inhomogeneous spin distribution. It is called spin-polarisation or spin injection. Spin-polarised current is the primary requirement to make semiconductor spintronics based devices. It is also very fragile state.

Therefore, the second problem is achieving transport of spin-polarised electrons maintaining their spin-orientation. Final problem, related to application, is relaxation time. This problem is even more important for the last category devices. Spin comes to equilibrium by the phenomenon called spin relaxation. It is important to create long relaxation time for effective spin manipulation, which will allow additional spin degree of freedom to spintronics devices with the electron charge. Utilizing spin degree of freedom alone or add it to mainstream electronics will significantly improve the performance with higher capabilities.

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