Alternating-field demagnetization: 1. A method for determining the stable component of remanent magnetization by partial demagnetization and removal of components with low coercive force. The specimen is placed in a space with nulled field (such as produced with Helmholz coils) and then subjected to an alternating magnetic field that is reduced gradually by decreasing the current of the field coil or by removing the specimen from the coil. 2. Reducing the magnetic field to zero to effect complete demagnetization to clean a magnetic tape (remove the data stored on it) so that the tape can be reused. A tape may be rotated during the demagnetization to remove the effect of the Earth’s magnetic field. Also called alternating-field demagnetization and degaussing.
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