Editing Remanence (section)

{{Short description|Magnetization left behind in a material}}
{{About|magnetic remanence|the data storage term|Data 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.<ref name=Chikazumi>{{Harvnb|Chikazumi|1997}}</ref> Colloquially, when a magnet is "magnetized", it has remanence.<ref>Strictly speaking, it is still in the Earth's field, but that has little effect on the remanence of a [[hard magnet]].</ref>  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".<ref>{{Cite web|url=https://www.etymonline.com/word/remanence|title=remanence {{!}} Origin and meaning of remanence by Online Etymology Dictionary|website=www.etymonline.com|language=en|access-date=2020-01-20}}</ref>

The equivalent term  '''residual magnetization''' is generally used in engineering applications. In [[transformer]]s, [[electric motors]] and [[Electric generator|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]].<ref>{{cite web|title=Magnetic Tape Storage and Handling|url=http://www.clir.org/pubs/reports/pub54/glossary.html}}</ref>