Gyromagnetic effect

Article By:

Abrahams, Elihu Department of Physics and Astronomy, University of California, Los Angeles, California.

Keffer, Frederic Department of Physics, University of Pittsburgh, Pittsburgh, Pennsylvania.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.303900

An effect arising from the relation between the angular momentum and the magnetization of a magnetic substance. It is the effect which is exploited in the measurement of the gyromagnetic ratio of magnetic materials. The gyromagnetic effect is demonstrated by a simple experiment in which a freely suspended magnetic substance is subjected to a magnetic field. Upon a change in direction of the magnetic field, the magnetization of the substance must change. In order for this to happen, the atoms must change their angular momentum. Since there are no external torques acting on the system, the total angular momentum must remain constant. Thus the sample must acquire a mass rotation which may be measured. In this way, the gyromagnetic ratio may be determined. Two common methods of determination are the Einstein-de Haas method and the Barnett method. See also: Gyromagnetic ratio

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