degaussing

Degaussing, or demagnetization, is the process of reducing or removing the magnetic field of an object by exposing it to an external magnetic field that is rapidly alternated and then gradually reduced. The method relies on the magnetic domains in ferromagnetic materials. An applied alternating field reorients the domains; as the field strength declines toward zero, the domains settle in random orientations, leaving little net magnetization and a diminished residual field.

The term degauss derives from the idea of removing magnetization, with “gauss” being a unit of magnetic flux density. The technique was developed in the 20th century and has found widespread use across electronics, display technology, manufacturing, and defense. In naval practice, degaussing refers to hull and equipment systems designed to minimize magnetic signatures to reduce sensitivity to mines, torpedoes, and other magnetic influences.

Applications span several domains. In consumer electronics, built‑in degaussing coils around cathode‑ray tube monitors and some televisions demagnetize components on startup to prevent color distortion and image artifacts. External degaussing units are used to erase data on magnetic storage media, such as tapes, and, in some cases, to sanitize equipment by removing residual magnetization. In industry, degaussing can restore or adjust magnetic properties of steel and other ferromagnetic parts after forming or processing.

Limitations and considerations include that some materials with strong anisotropy or high coercivity may retain residual magnetization despite degaussing. Degaussing a storage device typically destroys data irreversibly, so it is employed as a data-sanitization method rather than for reversible leveling of magnetism. For non-magnetic storage media, degaussing has little or no effect.