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

Giant magnetoimpedance (GMI) in amorphous (Fe0.06Co0.94)72.5B15Si12.5 wires (submitted to an alternative current, iac) has a dependence of the impedance response, Z, on direct current magnetic field, Hdc. In as-cast wires, the ac current frequency changes the GMI: for frequencies of a few kHz, the impedance response is a function of Hdc, having a single maximum at Hdc=0; for frequencies>1 MHz, however, two maxima (with a minimum at Hdc=0) are observed. By analyzing the frequency dependence of real, Lr, and imaginary inductance, Li (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 Lr and Li 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.