Magnetization dynamics of FeCuNbSiB soft magnetic ribbons and derived powder cores

In this study, the different character of magnetization mechanisms in as-quenched and annealed Fe73Cu1Nb3Si16B7 ribbon and derived nanocrystalline powder cores was studied by using very useful technique known as impedance spectroscopy. We investigated the dynamics and relaxation of the reversible and irreversible domain wall movements, as the dominant magnetization processes in the samples, by means of the effects of the increasing AC magnetic field amplitude on the complex permeability in a wide frequency range. In an amorphous ribbon, which was a precursor for preparation of powder cores, we observed two well-recognizable relaxation-dispersion regions corresponding to the domain wall displacements and bulging, respectively. The similar behavior was found for the annealed ribbon sample. However, in the bulk powder cores, only one dispersion region was present. From obtained complex permeability spectra, the interesting properties of the samples connected to their domain structure, such as relaxation frequencies of stepwise extinct magnetization processes and pinning fields, were extracted. All these phenomena were extensively discussed and the corresponding results for as-quenched and annealed ribbon and prepared bulk powder cores were confront.