Distinguish exchange coupling and dipolar interaction in FINEMET/FePt/FePd composite ribbons

In magnetic materials, the exchange coupling and dipolar interaction can significantly influence the magnetization processes, which was addressed in this paper by studying the system of FePt/FePd film deposited on FINEMET ribbon. In FINEMET/FePt/FePd composite ribbons, Giant magnetoimpedance effect (GMI) increased due to the contribution of the exchange coupling and dipolar interaction to the bias field (H_b) and resulted in an asymmetric characteristic of the GMI curves. Magneto-optical Kerr effect (MOKE) microscopy revealed typical transverse and longitudinal magnetic domain structure in FINEMET ribbon and FePd film respectively. Consequently, the FePd coating layer generated a H_b to the FINEMET ribbon and induced the asymmetry of GMI curves. The results also revealed that the generation of the H_b is mainly due to the exchange coupling and dipolar interaction between FePt, FePd coating layer and FINEMET ribbon. These two interactions can be clearly distinguished by exchange coupling and dipolar interaction models, which provides a valuable tool to study of the impact of the H_b on magnetic materials and could also extend the promise applications of AGMI in MI-based sensor devices.