colossal magnetoresistance abbr., CMR (rus. магнетосопротивление, колоссальное otherwise колоссальное магнитосопротивление abbr., КМС) — phenomenon of significant changes in electrical resistance of a sample placed in a strong magnetic field (by thousands and tens of thousands of percent).

Description

The CMR phenomenon is most characteristic of manganites, which usually demonstrate negative magnetoresistance, i.e. a significant drop in electrical resistance with increasing density of the magnetic field. It is suggested that this phenomenon may involve manganese - oxygen chains (double-exchange mechanism) or tunnelling of spin-polarised carriers across grain boundaries (tunnelling magnetoresistance). In both cases, the magnetic field causes ordering of the charge carrier spins; therefore the charge carriers can move more easily along the chains within the structure or by tunnelling between the microstructure elements.

The CMR values for manganites at cryogenic temperatures can exceed those for metallic multilayer heterostructures by several orders of magnitude. The effect is observed in strong magnetic fields, reaching its maximum when the intensity is in the order of several tesla. The phenomenon is called “colossal magnetoresistance”, since under the conditions specified, its value is much greater than the value of giant magnetoresistance. Colossal magnetoresistance is usually observed in a narrow temperature range near the Curie temperature. The higher the Curie temperature, the smaller is the magnetoresistance in the manganite. The CMR effect has been studied most deeply in lanthanum manganites and rare earth elements (R) of the series R1-xAxMnO3 (A = K, Na, Ag, Ca, Sr, Ba, Pb), but recently it has also been observed in some other complex oxides of transition metals. The phenomenon of CMR has been fully explained, neither by the existing theory of the magnetoresistance, nor by the double exchange mechanism.

CMR materials can be used as magnetic field sensors or as functional elements of spintronics devices.

Author

  • Zaitsev Dmitry D.

Source

  1. Gorbenko O.Ju., Bosak A. A. Magnetoresistance manganites at low magnetic fields and its application (in Russian)// Sensor. №2. 2002. 28–44pp.

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