Barnett effect
Template:Short description The Barnett effect is the magnetization of an uncharged body when spun on its axis.<ref name="Blaine">Template:Cite book</ref> It was discovered by American physicist Samuel Barnett in 1915.<ref>Template:Cite journal</ref>
An uncharged object rotating with angular velocity Template:Math tends to spontaneously magnetize, with a magnetization given by
- <math>M = \chi \omega / \gamma, </math>
where Template:Math is the gyromagnetic ratio for the material, Template:Math 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.