Demagnetisation
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Demagnetisation

Stan Zurek, Demagnetisation, Encyclopedia Magnetica,
http://e-magnetica.pl/doku.php/demagnetisation, {accessed: 2025-12-29}

Demagnetisation - an effect or process in which there occurs a reduction in the amount of net magnetisation of the material, sample, component, or device.¹⁾ The process of demagnetisation reverses the process of magnetisation.

See also the main article: Process of demagnetisation.

There are several specific meanings of “demagnetisation”, depending on the context:

Process of demagnetisation (or “degaussing”):
- by application of magnetic field
- by elevated temperature
Demagnetising field:
- Demagnetising factor
- Self-demagnetisation
Knee of demagnetisation

Degaussing (demagnetisation) by applying AC excitation and slowly reducing the amplitude. In the example as shown the degaussing is incomplete because there is still some remaining net magnetisation (position of the dot in the graph of the hysteresis loop). The reason for incomplete degaussing could be too low initial amplitude or too quick decrease of the AC excitation.²⁾

^{S. Zurek, E-Magnetica.pl, CC-BY-4.0}

Simplified illustration of demagnetisation: a) uni-directional excitation with magnetic field strength H with alternating and reducing amplitude causes the magnetic flux density B (related to the level of magnetisation M) so that the material can be demagnetised to the ideal point of H = 0, B = 0, and b) under two-dimensional or rotational magnetisation it might be more appropriate to reduce excitation in a form of a 2D (or even 3D) spiral, so that all the axial components such as B_x and B_y are reduced towards zero