The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2007 jointly to Albert Fert of France and Peter Grunberg of Germany. It is been awarded for their discovery of an entirely new physical effect known as Giant Magnetoresistance or GMR in 1988. The two scientists had independently discovered the effect in the same year that led to far reaching applications in the field of electronics and nanotechnology.
GMR is a quantum mechanical magnetoresistance effect observed in thin films that are composed of alternating ferromagnetic and nonmagnetic layers. It manifests itself as a significant decrease (typically 10-80%) in electrical resistance in the presence of magnetic field. In the absence of an external magnetic field, the direction of magnetization of adjacent ferromagnetic layers is anti-parallel due to a weak anti-ferromagnetic coupling between the layers resulting in high-resistance magnetic scattering due to electron spin. On applying an external magnetic field, the magnetization of the adjacent ferromagnetic layers is parallel resulting in lower magnetic scattering and lower resistance.
A system of this kind is the perfect tool for reading data from hard disks when information that is coded magnetically should be converted into electric current. In 1997, the first read out head that was based on the GMR was launched and that became the standard technology. A hard disk stores information in the form of microscopic small areas magnetized in different directions. The information is retrieved by a read out head that scans the disk and registers the magnetic changes. If the hard disk is smaller and more compact then it would require a more sensitive read out head to read the information on the disk. A read out head can convert very minute magnetic changes into differences in electrical resistance resulting in changes in the current emitted by the read-out head. The current is the signal from the read out head representing the ones and zeros. GMR can also be considered as one of the first real applications of the promising and evolving field of nanotechnology.