A Core–Shell Model for Magnetoimpedance in Stress-Annealed Fe-Rich Amorphous Microwires

The magnetoimpedance effect in a stress-annealed Fe-rich amorphous microwire with induced magnetic anisotropy in a surface region is studied theoretically. The static magnetization distribution within the microwire is described in the framework of the core–shell magnetic structure. It is assumed that the microwire has an axial magnetic anisotropy in the inner core and a helical anisotropy in the external shell appearing due to the stress-annealing. Both the diagonal and off-diagonal magnetoimpedance responses are found in terms of the surface impedance tensor. The influence of the bias current on the magnetoimpedance is analyzed. The obtained theoretical dependences are shown to be in a qualitative agreement with the results of recent experimental studies of the magnetoimpedance effect in stress-annealed Fe-rich glass–coated amorphous microwires.