Nonlinear electromagnetic response of ferromagnetic metals: Magnetoimpedance in microwires

Numerical calculations based on simultaneous solution of the Maxwell and Landau–Lifshitz equations were performed, in order to study the voltage response of ferromagnetic conductors carrying ac current. Since no significant approximations are made in the calculations, the model yields both linear and nonlinear giant magnetoimpedance (GMI) behavior and low and high power ferromagnetic resonance. Application to nonlinear GMI in ideal wires, with regions of uniform anisotropy, allows us to understand many aspects of the observed behavior and to predict phenomena such as solitary-wave-like propagation of the magnetization at fairly high current amplitude. Using appropriate magnetic structure, we were able to reproduce, with good agreement, the experimental observations for cobalt rich amorphous microwires. We have also found that even harmonics of GMI signal are very sensitive to the domain structure of the wire, whereas the odd harmonics are not.