Nonlinear giant magnetoimpedance and the asymmetric circumferential magnetization process in soft magnetic wires

The magnetoimpedance effect and its nonlinear terms are analysed for a (Co 0.94 Fe 0.06 ) 72.5 Si 12.5 B 15 amorphous wire. In order to enhance the nonlinear contribution the sample was previously subjected to current annealing (Joule heating) to induce a circumferential anisotropy. The effect of the application of a torsional strain on the nonlinear magnetoimpedance is analysed in terms of the torsional dependence of the magnetic permeability, evaluated through experimental circumferential hysteresis loops. The results obtained clearly confirm the direct correlation between the asymmetric circumferential magnetization process and the occurrence of nonlinear second-harmonic terms in the magnetoimpedance voltage.