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On different soft magnetic materials (such as pure Fe, Ni, Fe3% Si, Fe6.5% Si) the frequency dependence (from 0.5 to 50 Hz) of the hysteresis loop was measured on ring shaped samples. The samples were plastically deformed at different temperatures using the so-called high pressure torsion (HPT) method. From these data the frequency dependence of the coercivity for all samples can be deduced. A simple model based on eddy currents in the material is developed in order to describe the change of the coercivity with frequency. The most important parameter here is the relative permeability, which can be estimated from this model. The relative permeability was additionally determined from a plot of dB/dt versus the external field, which was in this case a triangular shaped H(t). The model parameters are compared and discussed. The internal stress due to the HPT treatment was estimated directly from the coercivity.