Frequency and Field-Intensity Dependences of Permeability of Soft Magnetic Films and their Expression Method

The permeabilities of soft magnetic films (sputtered CoNbTaZr) were measured under a wide range of field amplitudes (8 mOe to 8.5 Oe) at high frequencies (10 kHz to 1 MHz). In order to express the frequency (f) dependence of the permeability simultaneously with the field-intensity (Hex) dependence, a method for expressing the permeability characteristics was proposed employing constant-permeability contour lines in the Hex-f plane. It was found that such contour patterns reflect the process of magnetization of soft magnetic films in different areas of the Hex-f plane. The behavior of the contour lines for films with uniaxial magnetic anisotropy was investigated in particular. The permeabilities and magnetization processes are different for different manners of magnetic excitation, even at the same values of f and Hex. The difference may be attributed to the irreversible movement of magnetic domain walls.