giant magnetoresistance abbr., GMR (rus. магнетосопротивление, гигантское otherwise гигантское магнитосопротивление abbr., ГМС) — effect of change in electrical resistance of a sample placed in a magnetic field (mainly observed in heterostructures and superlattices); it differes from the magnetoresistance by the scale of effect (the resistance can be changed by tens of percents, while for the magnetoresistance the change does not exceed several percent).

Description

Giant magnetoresistance is observed in multilayer materials with alternating thin layers of ferromagnetic and nonmagnetic metals. Individual layers may be only a few atoms thick.

The resistance of such samples is high if the local magnetic fields of ferromagnetic materials are perpendicular and a minimum when they are parallel. The phenomenon was called “giant magnetoresistance”, since its value is much superior to that of common magnetoresistance. GMR was discovered in 1988-89 independently by two groups led by Albert Fert and Peter Gruenberg for which they were awarded the Nobel Prize in Physics in 2007. The phenomenon of giant magnetoresistance is used in hard drive reading heads and ultra-sensitive magnetic sensors.

In a number of cases colossal magnetoresistance (CMR) materials have advantages as compared with GMR-materials.

Illustrations

If layers of a ferromagnetic material (iron, Fe) alternate with thin layers of a non-magnetic m
If layers of a ferromagnetic material (iron, Fe) alternate with thin layers of a non-magnetic metal (chrome, Cr) with a specific thickness, the layers of the ferromagnetic will have alternating directions of magnetization (left). If this structure is placed in a fairly strong external field, all layers will have the same direction of magnetization (right).

Author

  • Zaitsev Dmitry D.

Sources

  1. Baklickaja O. Nobel Prizes in 2007 Giant magnetoresistance — a triumph of basic science (in Russian) // Nauka i zhizn'. 2007. №11. —www.nkj.ru/archive/articles/12042/ (reference date - 12.12.2011).
  2. The Discovery of Giant Magnetoresistance // Scientific Background on the Nobel Prize in Physics, 2007. The Royal Swedish Academy of Sciences, 2007. — 17 p. — http://nobelprize.org/nobel_prizes/physics/laureates/2007/phyadv07.pdf

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