Influence of stress relief on hysteretic magnetoimpedance in Co-rich amorphous ribbons at the relaxation frequency

Abstract.

The magnetoimpedance response shown by amorphous and nanostructured ultrasoft magnetic materials is a very promising effect suitable for application in a great variety of fields, as magnetic stress, strain or torsion sensors. However, magnetoimpedance hysteresis, which is related to irreversibilities in transverse magnetization processes, is an undesired effect for technological devices. Various thermal treatments were performed on Co-rich amorphous alloys to obtain quasi-reversible magnetoimpedance. Stress-relief-like treatments were found to reduce in a very significant way the hysteretic behaviour. Moreover, this improvement was analysed at the relaxation frequencies of the samples, where the magnetoimpedance has its maximum value. An attempt to understand the origin of this hysteresis reduction is given in this paper. The proposed explanation is based on the improvement of the reversibility in the magnetization processes, as a consequence of the decrease in the anelastic component of the induced anisotropy and the removal of wall pinning centres.