Correlation between structure, magnetic properties and MI effect during the nanocrystallisation process of FINEMET type alloys

Abstract

FeNbCuSiB metallic glasses show excellent soft magnetic properties in nanocrystalline state such as high saturation induction and permeability, low magnetostriction, coercive field and anisotropy, which make these materials very suitable for use in magnetic devices or sensors based on magnetoimpedance (MI) effect. The main aim of this paper is to emphasise the great importance of structure characterisation when a complete understanding of the magnetic behaviour is pursued. In this way, we present an exhaustive study of the correlation between the magnetic properties and the structural changes occurring along the crystallisation process, focusing our interest on the first stages of the crystallisation, where magnetic parameters, such as the magnetic permeability or the Curie temperature of the amorphous matrix, together with magnetic domain structure undergo more sensitive changes. Several experimental results obtained by means of X-ray and neutron diffraction, differential thermal analysis, thermomagnetization, Mössbauer spectroscopy, hysteresis loops and MI measurements or surface domain structure observation are presented and discussed.