Decomposition of magnetization processes in complex permeability spectra of 3% SiFe

Complex permeability spectra were measured as a function of the ac field amplitude h₀ and the cut angle a with respect to the [001] direction in a rectangular 3% SiFe sample. The spectra for α=0° at a relatively low field amplitude showed Debye-type dispersion with a relaxation frequency of 26.3 kHz. However, at a relatively high field amplitude, the spectra changed to a superposition of two dispersions, one with a relaxation frequency at 3.3 kHz and the other with a relaxation frequency at 26.3 kHz. Irreversible and reversible 180° domain wall motions were considered as mechanisms responsible for the h₀ dependent relaxation at 3.3 kHz and the h₀ independent relaxation at 26.3 kHz, respectively. From the a dependence of the spectra, we obtained another relaxation of the magnetization rotation, with a relaxation frequency of 0.16 MHz, in the original 180° domains for α≥70°.