Giant magnetoimpedance effect in a positive magnetostrictive glass-coated amorphous microwire -: art. no. 064402

The giant magnetoimpedance (GMI) effect in positive magnetostrictive glass-coated amorphous Co83.2Mn7.6Si5.8B3.3 microwire has been studied as a function of a de magnetic field - 140< H-dc < 140 Oe and frequency 0.1<f< 12.85 MHz. A maximum change of 43% in the MI of the as-quenched sample has been observed around 5 MHz frequency. Heat treatment of the sample by passing a dc current of 50 mA through it enhance.,; the MI value to a large extent (maximum change similar to94%) by increasing the outer domain Volume and inducing a transverse anisotropy. On the other hand, application of an external tensile stress reduces the GMI value by increasing the inner core domain and developing an axial anisotropy. In an as-quenched sample, the maximum value of MI is observed at H(dc)similar to0 when measured at frequency f<8 MHz beyond which a two peak MI profile is seen. The heat-treated sample shows this two peak behavior from a much lower frequency (below 1 MHz) and additional peaks at H-dc∼0 for f>10 MHz. Asymmetry in the MI peaks of a microwire has been produced by passing a dc current through the sample during impedance measurement, The magnetization of the as-quenched and heat-treated samples has also been studied to understand the domain structure and magnetoimpedance results.