Demagnetization

(electromagnetism) The process of reducing or removing the magnetism of a ferromagnetic material. The reduction of magnetic induction by the internal field of a magnet.
(mining engineering) Deflocculation in dense-media process using ferrosilicon by passing the fluid through an alternating-current field.

The reduction or elimination of the magnetic moment in an object; that is, the reverse of magnetization. It is commonly encountered as a procedure for eliminating the inadvertent magnetization of iron (or other ferromagnetic) parts of a sensitive mechanical device that would otherwise result in a malfunction. A suitably intense magnetic field applied in a direction opposite to that of the existing magnetization will serve to reduce or destroy that magnetization. (Alternatively, the material could, if practical, be heated to a temperature above its Curie point, then returned to room temperature, in the absence of any external magnetic field.) The adiabatic (isentropic) demagnetization of paramagnetic materials is a technique used to produce temperatures very near absolute zero. It has been used to cool and study a magnetic substance itself or, through thermal contact, a secondary substance (refrigeration). See also Adiabatic demagnetization; Ferromagnetism; Magnetization.