Magnetic properties of amorphous wires with different diameters

This paper presents a study of the GMI in amorphous conventional wires with nearly zero magnetostriction (Co68.18Fe4.32Si12.5B15) having different diameters obtained by cold drawing processes in multiple steps. The purpose of our work is to find the way in which the sensitivity of GMI effect is affected by the decrease of the wires diameter and also the way in which the stress induced during the cold drawing process influence the configuration of the magnetic domains structure through the modification of the magnetoelastic energy. The values of the impedance (Z) and GMI ratio (ΔZ/Z) were measured in the frequency range 100 kHz-100 MHz for wires in the as-cast state and cold drawn. We obtained a GMI ratio four times higher for cold-drawn wires with diameters of 20-30 μm subjected to thermo-mechanical treatments in comparison with the as-cast wire of 130 μm diameter.