Understanding of double-curvature shaped magnetoimpedance profiles in Joule-annealed and tensioned microwires at 8-12 GHz

TL;DR

This study explores how combined current and tensile stress influence the microwave magnetoimpedance profiles of Co-rich microwires, revealing a complex core-shell-shell magnetic structure that explains the double-curvature peaks.

Contribution

It introduces a novel core-shell-shell model to explain the double-curvature shaped MI profiles in microwires subjected to Joule annealing and tension at microwave frequencies.

Findings

Transformation of MI profiles from broad to sharp peaks with stress and current.

Identification of three magnetic regions: core, inner shell, outer shell.

Successful adaptation of the core-shell model to a core-shell-shell model.

Abstract

We have investigated for the first time the combined effect of current and stress on the GMI characteristics of vanishing-magnetostrictive Co-rich microwires at microwave frequency. As the current-annealed wire is subject to certain tensile stress, one can observe a drastic transformation of field dependence of MI profiles from smooth shape of a broad peak to deformed shape of a sharp peak with the emergence of a kink on each side. It follows that three different regions- core, inner and outer shell -have been formed by the combined effect of Joule annealing, current generated magnetic field and the tensile stress. A critical field sees a drop of field sensitivity from outer to inner shell and shifts to lower value with increasing annealing current. We successfully adapted our core-shell model to a core-shell-shell model by designating different anisotropy field for each region to satisfactorily resolve the unique double-curvature shaped peaks in the field derivative MI profiles.