Surface states of FeF2 (110) and its uncompensated magnetization

Abstract The (110) surface of iron fluoride (FeF2) is especially relevant to the understanding of the exchange bias phenomenon, which has important applications in the sensor industry, and has been extensively explored, both theoretically and experimentally. Here we investigate this FeF2 surface by means of ab initio techniques. We compute the (110) surface reconstruction, energetics, magnetic moments, band structure, charge density and electron localization function, for the two possible terminations (Fe and F). The surface reconstruction modifies the atomic and electronic structure of the free surface, yielding magnetism of a magnitude of 0.1 μ B per surface unit cell. Moreover, the charge density also changes, which alters the bonding in the vicinity of the surface. All these changes are expected to be relevant for exchange bias, that is once a ferromagnetic layer is deposited on the FeF2 surface.