Giant magneto-impedance effect in nanocrystalline glass-covered wires

Abstract

We investigate the evolution of the magneto-impedance (MI) response of Fe73.5Cu1Nb3Si13.5B9 glass-covered wires with the annealing temperature, starting from the as-cast amorphous state up to 600 °C. As-cast FeCuNbSiB amorphous glass-covered wires display a MI ratio of about 1%, this value increasing with the annealing temperature to about 5% for 550 °C when the nanocrystalline phase appears. For wires which have had the glass removed, the MI ratio increases from 5% for the as-cast amorphous state up to 28% after the appearance of the nanocrystalline phase. The MI is larger than that found in CoFeSiB amorphous wires after glass removal. Annealing over 550 °C leads to a decrease of the MI ratio for both glass-covered samples and samples with the glass coating removed. The results demonstrate the role of soft magnetic properties on the sensitivity of the MI effect.