  Giant magnetoresistance (GMR) is a quantum mechanical magnetoresistance
effect observed in thin film structures composed of alternating ferromagnetic
and nonmagnetic layers. The effect manifests itself as a significant decrease
(typically 10-80%) in electrical resistance in the presence of a magnetic
field. The effect is exploited commercially by manufacturers of hard disk
drives. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter
Grunberg for the discovery of GMR.
