Remanence

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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, hence the remanence is denoted as $B R$ (see the image).

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. Neodymium magnets, for example, have a remanence approximately equal to 1.3 teslas.