Giant magnetoimpedance modelling using Fourier analysis in soft magnetic amorphous wires

In this work, the Fourier analysis is employed to investigate the giant magnetoimpedance (GMI) effect in a FeCoSiB amorphous wire with vanishing magnetostriction In order to modify the initial quenched-in anisotropy, pieces 8 cm in length were submitted to Joule heating treatments below the corresponding Curie point. The induced circumferential anisotropy determines the field evolution of the electrical impedance of the sample upon the application of an axial magnetic field. The experimental results are interpreted within the framework of the classical electrodynamical theory where a simple rotational model is used to estimate the circular magnetization process of the sample. The mean value or the circumferential permeability is obtained through Fourier analysis of the time derivative of the estimated circular magnetization. Moreover, the existence of a second harmonic component of the GMI voltage is also experimentally detected. Its amplitude sensitively evolves with the axial DC magnetic field and its appearance is associated to an asymmetry in the circular magnetization process. (C) 2001 Elsevier Science B.V. All rights reserved.