Magneto-impedance response in ring shaped amorphous wires

The field dependence of the high frequency impedance in ring shaped CoFeSiB amorphous wires, has been investigated. Different results were obtained de pending on whether the applied de field was produced by a current from a co nductor passing through the middle of the ring, or by a magnetizing coil in which the ring was placed either parallel or perpendicular to the coil's a xis. The most sensitive magneto-impedance response was obtained in the firs t two cases, with a maximum magneto-impedance ratio (MIR) of about 40%. The impedance behavior in these ring shaped samples can be explained by consid ering the surface domain structure of the wires investigated, their non-mag netostrictive character, and the changes in the magnetization dynamics dete rmined by the increase of both frequency and de applied field. The possibil ity of using such,geometrical configuration as a field-sensing device is al so discussed. (C) 2001 Elsevier Science B.V. All rights reserved.