Influence of Joule heating on magnetostriction and giant magnetoimpedance effect in a glass covered CoFeSiB microwire

The influence of annealing parameters (time $t_a,$ current $I_a,$ and applied stress ${\sigma }_a)$ on magnetic properties of Joule heated amorphous ${\mathrm{Co}}_{\mathrm{68.15}}{\mathrm{Fe}}_{\mathrm{4.35}}{\mathrm{Si}}_{\mathrm{12.5}}{\mathrm{B}}_{\mathrm{15}}$ glass covered microwire (13 μm) was investigated. Annealing under applied stress induces additional anisotropy which is proportional to ${\sigma }_a$ and can be removed by subsequent heating without stress. The magnetoimpedance, measured on the sample with the lowest anisotropy field ${\mathrm{(H}}_K\text{≈120\hspace{0.5em}}{\mathrm{Am}}^{\mathrm{-1}}\mathrm{),}$ shows sharp maxima at ${\mathrm{H=\pm H}}_K.$ For driving currents higher than 0.2 mA nonlinear behavior is observed, and the magnitude of giant magnetoimpedance significantly decreases. The maximum relative change of impedance (60%), observed for the highest frequency, 900 kHz, compares well with the values reported on conventional wires.