STRESS DEPENDENCE OF THE GIANT MAGNETO-IMPEDANCE EFFECT IN AMORPHOUS WIRES

The recently discovered giant magneto-impedance (GMI) effect has been measured as a function of circular driving-held frequency and applied tensile stress on two near-zero-magnetostriction amorphous wires. The effect of different orientations of the induced magnetoelastic anisotr opy has been verified, for the first time, by using wires with opposit e magnetostriction constant, lambda(S), signs (Fe4.9Co71.8Nb0.8Si7.5B1 5, lambda(S) = 1.5 x 10(-7); and Co68.1Fe4.4Si12.5B15, lambda(S) = -4 x 10(-8)). GMI ratios up to 300% were found in the magnetically softer (lower-magnetostriction) wire. The frequency dependence of GMI has be en found to be strongly influenced by the magnetoelastic anisotropy in duced in the amorphous wires. Results are interpreted in terms of chan ges in the magnetic penetration depth by modifications in the circumfe rential permeability originated by the action of external agents as fi eld and mechanical stresses. GMI is therefore found to be largely dete rmined by the magnetic domain configuration and relative contributions of both domain wall motions and magnetic moment rotations to the over all magnetization process.