Article
Article
Demagnetization
Article By:
Hall, Michael National Physical Laboratory, Middlesex, United Kingdom.
Last reviewed:January 2020
DOI:https://doi.org/10.1036/1097-8542.183600
The process of reducing the retained level of magnetization (remanence) in an object. Demagnetization is necessary because the ferromagnetic elements iron, nickel, and cobalt and their alloys can become permanently magnetized if they are exposed to a magnetic field. There is a vast range of sizes of objects whose magnetization would degrade their performance. Examples range from mine-sweeping ships, through magnetic shields for cathode-ray tubes, down to even smaller objects. The level retained and the field required to demagnetize depend on their ferromagnetic behavior. Permanent magnets are called “hard” and are required to retain magnetization since it is this property that makes them useful. The magnetic materials used in transformers are called “soft” and here the retention of magnetization could detrimentally alter the performance of the transformer.
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