Origin of asymmetrical magnetoimpedance in a Co-based amorphous microwire due to dc bias current

Permeability spectra and asymmetrical giant magnetoimpedance (AGMI) have been studied in a Co-based amorphous microwire upon the application of a dc biasing current together with a shift of axial hysteresis loops. The permeability from wall motion of core domains is nearly constant, but the permeability from rotational magnetization of shell domains increases with the bias current. AGMI and its field sensitivity are realized for the bias current due to the influence of a unidirectional bias field on wall motion in the circumferential direction. In addition, helical internal anisotropy in this microwire also plays a significant role in responding differently to the axial magnetization process and thus to AGMI. The helical residual stress is estimated to be smaller in Co-based amorphous wire than that in Fe-based amorphous wire.