Giant magnetoresistance (GMR) is a quantum mechanical effect observed in thin films made of alternating layers of ferromagnetic and non-magnetic materials. It manifests as a significant change in electrical resistance in response to an applied magnetic field. The phenomenon was first discovered in the 1980s by Albert Fert and Peter Grünberg, who were awarded the Nobel Prize in Physics in 2007 for their work on GMR.
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Introduction to Spintronics by Aurélien Manchon (2020) giant magnetoresistance section
. Source. Describes how giant magnetoresistance was used in magnetoresistive disk heads in the 90's providing a huge improvement in disk storage density over the pre-existing inductive sensors
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