Studies of domain wall motion. III. The field dependence of differential susceptibility at the early stage of magnetization

For pt.II see ibid., vol.3, p.4783 (1991). Differential susceptibilities chi diff of nickel wire, Permalloy-42 wire, 4% silicon iron sheet and bars of SAE 1015 and 1045 steels were measured when undergoing uniform magnetic field sweeping. The field dependences of chi diff of wires, sheet and bars at the early stage of magnetization were studied: in general, chi diff decreases with increasing sweep rate of field and the chi diff-H relationship depends on sample shape. The experimental results are interpreted using a phenomenological model based on domain wall (DW) motion that it is modest generalization of the Rayleigh law at low field. This model is also compared with a previous model of magnetomechanical damping.