Barnett effect

From Wikipedia, the free encyclopedia
Jump to: navigation, search

The Barnett effect is the magnetization of an uncharged body when spun on its axis.[1] It was discovered by American physicist Samuel Barnett in 1915.[2]

An uncharged object rotating with angular velocity ω tends to spontaneously magnetize, with a magnetization given by:

M=\chi \omega / \gamma \ ,

with γ = gyromagnetic ratio for the material, χ = magnetic susceptibility.

The magnetization occurs parallel to the axis of spin. Barnett was motivated by a prediction by Owen Richardson in 1908, later named the Einstein-de Haas effect, that magnetizing a ferromagnet can induce a mechanical rotation. He instead looked for the opposite effect, that is, that spinning a ferromagnet could change its magnetization. He established the effect with a long series of experiments between 1908 and 1915.

See also

References

  1. ^ Bruce T. Draine (2003). "§7.3 Barnett effect". In Andrew W. Blain, F. Combes, Bruce T. Draine, D. Pfenniger, Yves Revaz. The Cold Universe. Springer. p. 276. ISBN 3-540-40838-X. 
  2. ^ Barnett, S. J. (1915). "Magnetization by Rotation". Physical Review 6 (4): 239–270. Bibcode:1915PhRv....6..239B. doi:10.1103/PhysRev.6.239. 

Further reading