Exchange bias and its propagation in ferromagnetic/antiferromagnetic/ferromagnetic trilayers

Abstract

We establish a simple ferromagnetic/antiferromagnetic/ferromagnetic trilayer model, where the lower-interface coupling is varied and study its combined effect with cooling field or temperature on the upper-interface exchange bias effect. Exchange bias field is almost independent of cooling field, if the lower-interface coupling is ferromagnetic and large. Otherwise, its value becomes sensitive to cooling field, and the evolution trend of exchange bias with increasing cooling field depends on the sign and strength of lower-interface coupling. On the other hand, the blocking temperature, below which exchange bias emerges, is reduced (or elevated) in the trilayers with a large ferromagnetic (or antiferromagnetic) lower-interface coupling. The numerical results obtained are interpreted well in terms of the magnetization behaviors in the respective layers. A cooling field creates a low-temperature frozen configuration in the antiferromagnetic layer after cooling to generate exchange bias, while such a configuration related to exchange bias and blocking temperature may be rearranged due to existence of the second ferromagnetic layer on the backside of the antiferromagnetic layer. This work provides an insight into the exchange bias effect and its propagation in such a trilayer stack employing a rather thin antiferromagnetic layer.