Remanence, Br

(De-) magnetization curve - BH curve = hysteresis curve

When a periodically alternating external magnetic field H is applied, the magnetization of a ferromagnetic material follows a magnetization curve. Starting from 'virgin' material without net magnetization, we follow the blue curve the first time we do this (see image below). Upon reaching the saturation flux density - with magnetic field strength Hs - the magnetization does not increase further.

Remanent field strength BR

If we then invert the field, the magnetization at field strength H = 0 has not fully decreased to zero. There is a remanent field strength BR left as a result of the ‘Weiss domains’ not returning to their original state.

For more information see the explanation under hysteresis curve.