Barnett effect
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:
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.
In-line references and notes
- ^ 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 354040838X. http://books.google.com/books?id=A6ceYPsxsSEC&pg=PA276.
- ^ 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
- S. J. Barnett, Magnetization by Rotation, Physical Review, Vol. 6, Issue 4, pp. 239–270 (1915). [1]
- S. J. Barnett, Gyromagnetic and Electron-Inertia Effects, Review of Modern Physics, Vol. 7, Issue 2, pp. 129–166 (1935). [2]