Exchange bias in Fe/FeF2 and Fe/MnF2 model systems

The exchange bias (EB) is a unidirectional magnetic anisotropy that is found in structures containing exchange-coupled ferromagnetic/antiferromagnetic interfaces. The EB usually manifests as a horizontal shift of the hysteresis after cooling the system through the Néel temperature of the antiferromagnet in the presence of an external magnetic field. A vertical shift and an asymmetry of the magnetization loop are also possible. At present, the EB is often investigated for its effect on an application in magnetic devices in a variety of material systems and applications. The EB bilayer systems Fe/FeF2 and Fe/MnF2 represent an interesting case of structural similarities. In this paper, we show that differences between magnetic material orders and disorder contributions, found at the microscale, make them model systems for the occurrence of specific magneto-crystalline anisotropies and specific angular dependencies of the EB with significant implications for magneto-electronic applications.