A model for asymmetric giant magnetoimpedance in field-annealed amorphous ribbons

A phenomenological model for the asymmetric giant magnetoimpedance (GMI) in field-annealed amorphous ribbons is developed. The effect of a surface crystalline layer on the GMI response is described in terms of an effective bias field appearing due to a coupling between the crystalline layer and amorphous phase. It is shown that the presence of the bias field changes drastically the GMI profile. At low frequencies, the domain-walls motion leads to a steplike change in the GMI response. At high frequencies, the domain-walls motion is damped, and the GMI profile exhibits asymmetric two-peak behavior. The calculated dependences are shown to be in a qualitative agreement with results of experimental studies of the asymmetric GMI in field-annealed Co-based amorphous ribbons.