Noncollinear anisotropy mediated magnetization reversal in <i>L</i> 10 FePt/FeCo exchange-bias bilayers

Abstract

The exchange bias effect is widely used in spintronic devices, promoting development in the field of spintronics. Studying the angular dependence of exchange bias (ADEB) in antiferromagnetic/ferromagnetic systems contributes to a deeper understanding of the exchange bias effect and the accompanying asymmetric magnetization reversal. Compared to collinear anisotropy systems, noncollinear anisotropy systems exhibit richer characteristics in magnetization reversal behavior. However, in hard magnetic (HM)/soft magnetic (SM) systems, the underlying mechanisms of ADEB in noncollinear anisotropy configurations remain inadequately explained. In this work, micromagnetic simulations are utilized to study the exchange bias effect and asymmetric magnetization reversal in the FeCo layer of the L10 FePt (HM)/FeCo (SM) bilayer thin film with noncollinear anisotropy. The results indicate that the relative orientations between the applied magnetic field, unidirectional anisotropy, and uniaxial anisotropy can alter the magnetization reversal mechanism of the FeCo layer. The angular dependence of the exchange bias field, coercivity, and asymmetry of the hysteresis loop shows diverse characteristics as the noncollinear angle varies. Furthermore, asymmetric magnetization reversal is manifested not only in the asymmetry between the descending and ascending branches of the hysteresis loop but also in the inconsistency of the direction of magnetic domain diffusion. These insights will provide additional perspectives for the application of the exchange bias effect in spintronic devices.