Exchange induced unidirectional anisotropy at FeMn-Ni₈₀Fe ₂₀ interfaces

We have systematically investigated exchange coupled films of sputter deposited Ni80Fe20/FeMn and FeMn/Ni80Fe 20 and obtained films with high exchange bias and low coercive forces. The variation of film properties with deposition conditions as well as with the permalloy and FeMn thicknesses have also been studied. The results demonstrated a strong dependence of exchange bias effect (HUA) on the amount of γ-phase FeMn, the amount of impurities, as well as the abruptness of the transition profile at the interface. In addition, our results have also raised a number of new questions concerning the magnetic state of the interface and the origin of the interface coupling phenomena.