Stress dependence of the giant magneto-impedance effect in amorphous wires

Abstract

The recently discovered giant magneto-impedance (GMI) effect has been measured as a function of circular driving-field frequency and applied tensile stress on two near-zero-magnetostriction amorphous wires. The effect of different orientations of the induced magnetoelastic anisotropy has been verified, for the first time, by using wires with opposite magnetostriction constant, lambda s, signs (Fe4.9Co71.8Nb0.8Si7.5B15, lambda S=1.5*10-7, and Co68.1Fe4.4Si12.5B15, lambda S=-4*10-8). GMI ratios up to 300% were found in the magnetically softer (lower-magnetostriction) wire. The frequency dependence of GMI has been found to be strongly influenced by the magnetoelastic anisotropy induced in the amorphous wires. Results are interpreted in terms of changes in the magnetic penetration depth by modifications in the circumferential permeability originated by the action of external agents as field and mechanical stresses. AMI is therefore found to be largely determined by the magnetic domain configuration and relative contributions of both domain wall motions and magnetic moment rotations to the overall magnetization process.