Giant magnetoimpedance in glass-covered amorphous microwires

GMI was investigated in amorphous Co-rich glass-covered microwires with very low magnetostriction constant. Internal stresses, induced in the metallic core by the glass coating, substantially reduce the magnitude of GMI. To improve GMI properties magnetoelastic coupling was reduced by a careful choice of alloy composition and by subsequent Joule-heat treatment. The maximum magnetoimpedance, DeltaZ/Z approximate to 600% measured at frequency 15 MHz, is already close to the theoretical value (1060%) and is one of the highest GMI amplitudes ever reported. (C) 2002 Elsevier Science B.V. All rights reserved.