Remanence

Remanence or remanent magnetization or residual magnetism is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed.^[1] Colloquially, when a magnet is "magnetized", it has remanence.^[2] The remanence of magnetic materials provides the magnetic memory in magnetic storage devices, and is used as a source of information on the past Earth's magnetic field in paleomagnetism. The word remanence is from remanent + -ence, meaning "that which remains".^[3] The origins of remanence originate from some point after 1850.^[4]

The equivalent term residual magnetization is generally used in engineering applications. In transformers, electric motors and generators a large residual magnetization is not desirable (see also electrical steel) as it is an unwanted contamination, for example, a magnetization remaining in an electromagnet after the current in the coil is turned off. Where it is unwanted, it can be removed by degaussing.

Sometimes the term retentivity is used for remanence measured in units of magnetic flux density.^[5]

^ Chikazumi 1997
^ Strictly speaking, it is still in the Earth's field, but that has little effect on the remanence of a hard magnet.
^ "remanence | Origin and meaning of remanence by Online Etymology Dictionary". www.etymonline.com. Retrieved 2020-01-20.
^ "5.01.3.1 Early Observation of the Remanence of Rocks". www.sciencedirect.com. Retrieved 2024-08-02.
^ "Magnetic Tape Storage and Handling".

[Chikazumi-1] Chikazumi 1997

[2] Strictly speaking, it is still in the Earth's field, but that has little effect on the remanence of a hard magnet.

[3] "remanence | Origin and meaning of remanence by Online Etymology Dictionary". www.etymonline.com. Retrieved 2020-01-20.

[4] "5.01.3.1 Early Observation of the Remanence of Rocks". www.sciencedirect.com. Retrieved 2024-08-02.

[5] "Magnetic Tape Storage and Handling".

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