Correlation between magnetization processes and giant magnetoimpedance response in CoFeBSi amorphous CoFeBSi wires

Giant magnetoimpedance (GMI) in amorphous (Fe 0.06 Co 0.94 ) 72.5 B 15 Si 12.5 wires (submitted to an alternative current, i ac ) has a dependence of the impedance response, Z, on direct current magnetic field, H dc . In as-cast wires, the ac current frequency changes the GMI: for frequencies of a few kHz, the impedance response is a function of H dc , having a single maximum at H dc = 0; for frequencies >1 MHz, however, two maxima (with a minimum at H dc = 0) are observed. By analyzing the frequency dependence of real, L r , and imaginary inductance, L, (proportional to real and imaginary permeability, respectively), we show that these results can be explained in terms of the dominant magnetization process: domain wall bulging for low frequencies and magnetization rotation for high frequencies. Plots of both L r and L, as a function of frequency indicate relaxation processes at about 45 kHz, due to a change from domain wall to spin rotation as the dominant magnetization process.