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 Co68.15Fe4.35Si12.5B15 glass covered microwire (13 mu m) was investigated. Annealing under applied stress induces additional anisotropy which is proportional to sa and can be removed by subsequent heating without stress. The magnetoimpedance, measured on the sample with the lowest anisotropy field (H-K approximate to 120 Am-1), shows sharp maxima at H = +/- 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. (C) 1999 American Institute of Physics. [S0021-8979(99)17108-1].