{{Short description|Magnetization of an uncharged body when spun on its axis}} The '''Barnett effect''' is the magnetization of an uncharged body when spun on its axis.<ref name="Blaine">{{cite book |title=The Cold Universe |author=Bruce T. Draine |editor1=Andrew W. Blain |editor2=F. Combes |editor3=Bruce T. Draine |editor4=D. Pfenniger |editor5=Yves Revaz |page=276 |chapter-url=https://books.google.com/books?id=A6ceYPsxsSEC&pg=PA276 |isbn=3-540-40838-X |year=2003 |chapter=§7.3 Barnett effect |publisher=Springer}}</ref> It was discovered by American physicist Samuel Barnett in 1915.<ref>{{cite journal | last = Barnett | first = S. J. | title = Magnetization by Rotation | year = 1915 | journal = Physical Review | volume = 6 | issue = 4 | pages = 239–270 | doi = 10.1103/PhysRev.6.239 |bibcode = 1915PhRv....6..239B }}</ref>
An uncharged object rotating with angular velocity {{math|''ω''}} tends to spontaneously magnetize, with a magnetization given by : <math>M = \chi \omega / \gamma, </math> where {{math|''γ''}} is the gyromagnetic ratio for the material, {{math|''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 == * London moment
==References== {{reflist}}
==Further reading== * {{cite journal |url=https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.7.129 |author=S. J. Barnett |title=Gyromagnetic and Electron-Inertia Effects |journal=Reviews of Modern Physics |volume=7 |issue=2 |pages=129–166 |year=1935 |doi=10.1103/RevModPhys.7.129|bibcode=1935RvMP....7..129B |url-access=subscription }}
Category:Magnetism
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