remanence

A family of hysteresis loops for grain-oriented electrical steel (B_R denotes remanence and H_C is the coercivity.

Remanence is the magnetization left behind in a medium after an external magnetic field is removed. It is denoted in equations as M_r. In engineering applications it is often assumed that the magnetization M is synonymous with the residual flux density B (they differ by a factor of μ₀, B_R = μ₀M) hence the remanence is frequently denoted as B_R (see the image). Only substances that can be magnetized, ferromagnetic and ferrimagnetic materials such as iron, have remanence.

The remanence magnitude can be taken from a hysteresis loop at the intersections of the loop with the vertical magnetization axis. It can be measured with a B-H Analyzer.

Remanence has application in:

• geology (concerning paleomagnetism)
• computer engineering (concerning data storage and recovery, see data remanence)
• physics (concerning magnetism).

The value of remanence is one of the most important parameters characterising permanent magnets; it measures the strength of their magnetic field. Neodymium magnets, for example, have a remanence approximately equal to 1.3 teslas.

References

• R. V. Lapshin (1995). "Analytical model for the approximation of hysteresis loop and its application to the scanning tunneling microscope" (PDF). Review of Scientific Instruments (USA: AIP) 66 (9): 4718-4730. doi:10.1063/1.1145314. ISSN 0034-6748. http://www.nanoworld.org/homepages/lapshin/publications.htm#analytical1995.  (Russian translation is available).

External links

• Coercivity and Remanence in Permanent Magnets
• Magnet Man

See also

• retentivity
• Coercivity
• hysteresis

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