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Nonlinear but lossless ferromagnet

For larger field strengths, the behaviour of a ferromagnet is better described by the hysteresis

cun/e shown in Figurę 5.1. In relation to that curve we take the opportunity to define in the figurę the important concepts of saturation magnetisationMoand coercive force Hc.

If the hysteresis loop is relatively narrow, and we are prepared to accept a rather crude

approximation, we could write M=_Xm(H)H (5.14)

where Xm(H) is the field-dependent non-linear magnetic susceptibility. This model corresponds to the dielectric model of equation 5.5, and has approximately the same relativelyuninterestinguses.