Helical anisotropy and Matteucci effect in Co-Si-B amorphous wires with negative magnetostriction (abstract)

Abstract

The Co-Si-B amorphous wires having the negative magnetostriction comprises shell and core domains and exhibits the re-entrant flux reversal as the Fe-Si-B wire with positive magnetostriction. One of the characteristic features of Co based wires is that a sharp pulse voltage generation between two wire ends (Matteucci effect) is accompanied with re-entrant flux reversal, which is useful for sensor application because of no need for sense windings. In this work, we studied the origin of the large Matteucci effect of Co-Si-B wires by domain observation with a Kerr microscope and by Sixtus–Tonks experiments by driving the reverse domain propagation with the circular fields generated by the current through wires. We also tried to measure the hysteresis loop in the circular direction by integrating the Matteucci voltage. It was found that the domain patterns of the Co-Si-B wire surface is not the previously reported bamboo configuration but the helical configuration. Most of the anisotropy of the amorphous materials is magnetostrictive in origin. The helical anisotropy of Co based wire seems consistent, if we assume the same residual stress distribution as in the steel rod quenched into the water. Because of the helical anisotropy, the Co wire has the big circular component of magnetization in the core domain as well as in the shell domain, and both domain can interact near the interface region. It was found that reverse domain propagation along the wire axis can be caused by application of the circular field and that the shell domain moves discontinuously during the re-entrant flux reversal in the core domain. These circular magnetization components in both core and shell domains due to helical anisotropy and their interaction seems responsible for the large Matteucci effect in the Co-Si-B wires.