Validity of the Stoner-Wohlfarth model in hysteretic giant magnetoimpedance of annealed amorphous materials

The hysteretic characteristics of giant magnetoimpedance (GMI) profiles have been measured in Co-based amorphous ribbon with various anisotropy angles θ_k, and they have been analyzed by using the Stoner-Wohlfarth model. A two-peak behavior with a dip near zero field is revealed in the measured GMI profile at 10 MHz, irrespective of θ_k. The negligible hysteresis of the field for the dip is in close agreement with that calculated assuming a magnetization jump from a metastable to a stable state. However, the hysteretic asymmetries for the increasing and decreasing fields in the samples with the angle range of 20°≤θ_k <_k60° are well described by a divergence in the calculation without a magnetization jump. The asymmetry for the sample with θ_k≥60° may also be due to the divergence. But the two peak of the measured profiles, which are due to the anisotropy distribution in the actual materials, are different from the calculated profiles, which have a single peak near zero field. This indicates that the Stoner-Wohlfarth model adequately describes a hysteretic asymmetry of GMI profiles for the anisotropy angle in the range of 20° ≤ θ_k <60° at a frequency of 10 MHz in amorphous ribbons.