Physics: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
- [math]\displaystyle{ M = \chi \omega / \gamma, }[/math]
where γ is the gyromagnetic ratio for the material, χ is the 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
- ↑ Bruce T. Draine (2003). "§7.3 Barnett effect". The Cold Universe. Springer. p. 276. ISBN 3-540-40838-X. https://books.google.com/books?id=A6ceYPsxsSEC&pg=PA276.
- ↑ Barnett, S. J. (1915). "Magnetization by Rotation". Physical Review 6 (4): 239–270. doi:10.1103/PhysRev.6.239. Bibcode: 1915PhRv....6..239B.
Further reading
- S. J. Barnett (1935). "Gyromagnetic and Electron-Inertia Effects". Reviews of Modern Physics 7 (2): 129–166. doi:10.1103/RevModPhys.7.129. Bibcode: 1935RvMP....7..129B. http://prola.aps.org/abstract/RMP/v7/i2/p129_1.
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