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The head GMR is one of the three types of play-back heads existing on the hard drives.

GMR means Giant MagnetoResistance

A head GMR is comparable, in its structure, with a magnétorésistive head. The writing continues to be assured by an inductive head. The reading, as for it, rests on a phenomenon discovered by two physicists (Albert Fert and Peter Grunberg Nobel Prize 2007). As with a magnétorésistive head, one measures the changes affecting the electrical resistance of an element placed in the vicinity of a magnetic field, but the device implements materials in extremely thin layers whose answer is much stronger than that obtained with the magnétorésistif process (from where the term giant ). The device being more sensitive, one can exploit magnetic traces much smaller on the disc.

Principle of magnetic heads GMR

With heads GMR, the writing is always ensured by an inductive head. The reading on the other hand, rests on the quantum property that an electron can have two spins. When the spin is parallel to the orientation of the magnetic field of the hard drive, a low electrical resistance is generated, on the other hand when the spin is of opposed direction, a strong resistance is observed.

The device being more sensitive, one can exploit magnetic traces much smaller on the disc. Thanks to the sensitivity of effect GMR, one can detect smaller fields, therefore to register smaller bits, i.e. to increase the density of information stored in the disc. Since their arrival on the market in 97, the density of storage of heads GMR increased by a factor higher than 100.

Beyond heads GMR

The GMR is a simple but industrially effective process to act on the spin of the electrons and to control the circulation of those. But the longer-term ambitions of the discipline aim at handling the spin on a each electron scale, using suitable devices. The prospects for miniaturization, just like speed of execution of such devices would then exceed all that micro-electronics let to us foresee until there. Let us recall that to date, our computers exploit macroscopic flows of electrons (i.e traditional electric currents) whose intensity makes it possible to record, to read, transmit or process binary data.

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