====== Demagnetisation ======

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| //[[user/Stan Zurek]], Demagnetisation, Encyclopedia Magnetica//, \\ @PAGEL@, {accessed: @YEAR@-@MONTH@-@DAY@} |

**Demagnetisation** - an effect or process in which there occurs a reduction in the amount of net [[magnetisation]] of the material, sample, component, or device.[(Zurek>[[https://isbnsearch.org/isbn/9780367891572|S. Zurek, Characterisation of Soft Magnetic Materials Under Rotational Magnetisation, CRC Press, 2019, ISBN 9780367891572]])] The process of demagnetisation reverses the [[process of magnetisation]].

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| {{/wiki/logo.png?20&nolink}} //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]]

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[[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.[(Zurek)]
[[file/ac_demagnetisation_example_png|{{2dmch4/ac_demagnetisation_example.png}}]]
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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<sub>x</sub>// and //B<sub>y</sub>// are reduced towards zero
[[file/ac_and_rotational_demagnetisation_png|{{2dmch4/ac_and_rotational_demagnetisation.png}}]]
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===== See also =====
  *[[Demagnetisation]]
  *[[Process of demagnetisation]]
  *[[Process of magnetisation]]
  *[[Degaussing]]
  *[[Demagnetising field]]



===== References =====
~~REFNOTES~~

{{tag> Demagnetisation Process_of_demagnetisation Degaussing Demagnetising_field Counter}}