College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
Giant Magnetoresistance (GMR) is a quantum mechanical magnetoresistance effect observed in thin film structures composed of alternating ferromagnetic and non-magnetic conductive layers. It results in significant changes in electrical resistance in response to applied magnetic fields.
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GMR was discovered independently by Albert Fert and Peter Grünberg in 1988, who later won the Nobel Prize in Physics in 2007 for this discovery.
The effect arises due to the spin-dependent scattering of electrons at the interfaces between ferromagnetic and non-magnetic layers.
GMR is used extensively in read heads for modern hard disk drives, enabling higher storage densities.
The phenomenon can be explained using the two-current model where electron spins are treated separately as up-spin and down-spin currents.
In a GMR device, when the magnetizations of adjacent ferromagnetic layers are parallel, the resistance is low; when they are antiparallel, the resistance is high.
Review Questions
What causes the change in electrical resistance observed in giant magnetoresistance?
How does the alignment of magnetizations in ferromagnetic layers affect GMR?
Name an application of GMR technology and explain its significance.
Related terms
Ferromagnetism: A type of magnetism where magnetic moments of atoms align within a material to create a strong magnetic field.
Spintronics: A field of study that focuses on the intrinsic spin of electrons and its associated magnetic moment, alongside charge-based electronics.
Magnetoresistance: The tendency of a material's electrical resistance to change when subjected to an external magnetic field.