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.