Giant magnetoimpedance of glass-covered amorphous microwires of Co-Mn-Si-Band Co-Si-B

A study of magnetic hysteresis and giant magnetoimpedance (GMI) in amorphou s glass-covered Co-Si-B and Co-Mn-Si-B wires is presented. The wires, about 10 mu m in diameter, were obtained by a glass-coated melt spinning techniq ue. Samples with positive magnetostriction (MS) have a rectangular bistable hysteresis loop. A smooth hysteresis loop is observed for wires with nearl y zero MS. When the MS is negative, almost no hysteresis is observed. The G MI was measured in the frequency range between 20 Hz and 30 MHz. The shapes of the impedance versus field curves are qualitatively similar to each oth er for both positive and zero MS samples. The impedance is maximum at zero field, and decreases sharply in the range of 10-20 Oe. For the negative MS wires, when the driving current is small, the impedance is maximum at a fin ite external field. The position of the maximum approaches zero with increa sing current. The contributions of the moment rotation and domain wall moti on in the three cases are discussed. (C) 1999 American Institute of Physics . [S0021-8979(99)34508-4].