A phenomenological model for the asymmetric giant magnetoimpedance (GMI) in fieldannealed 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.

The asymmetric giant magnetoimpedance (GMI) profile has been realized in weak-field-annealed Co-based amorphous ribbon at the annealing temperature of 380 °C in open air. Asymmetric GMI profiles with respect to applied field become profound as the annealing field increases over 500 mOe. The asymmetric GMI profile at the frequencies of ac current over 0.5 MHz is well ascribed for by the rotational transverse magnetization of single domain under a uniaxial anisotropy in amorphous core and a unidirectional anisotropy due to the exchange coupling with the bias field in the crystalline layer, underlying surface oxidation layer developed during the annealing in open air.

In a Comment [D. X. Chen, L. Pascual, and A. Hernando, Appl. Phys. Lett. 77, 1727 (2000)] on our recent letter [C. G. Kim, K. J. Jang, D. Y. Kim, and S. S. Yoon, Appl. Phys. Lett. 75, 2114 (1999); 76, 1345 (2000)] Chen et al. claimed that the unidirectional anisotropy due to bias field is unphysical one for the description of asymmetric giant magnetoimpedance (GMI) profiles. The symmetric two peaks of GMI profiles measured in the normal sample with an uniaxial anisotropy, allow one to take the minimum energy condition which assumes a jump of magnetization under the field from a metastable state to a stable one. However, the divergence in a calculated GMI profile should appear even in case of a uniaxial anisotropy of normal sample where there is no jump. Divergence indicates the asymmetry and hysteresis in GMI profile. The analysis of this calculation in Chen et al.’s Comment is simply a matter of hysteresis in GMI profile for the increasing and decreasing field, even in a normal sample with uniaxial anisotropy. Even though the hysteresis is ignored by taking the minimum energy condition, the asymmetric profiles with the negligible hysteresis are well ascribed by the model with two kinds of anisotropy fields, as proposed in our previous letter [C. G. Kim, K. J. Jang, D. Y. Kim, and S. S. Yoon, Appl. Phys. Lett. 75, 2114 (1999); 76, 1345 (2000)]. In this model the bias field is quite physical, and is based on the observed experimental results in a specially prepared sample.

No abstract

No abstract