A brief introduction to giant magnetoresistance
  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. 
Liu Chang, Min Wang, Lei Liu, Siwei Luo, Pan Xiao
cond-mat.mtrl-sci