Finite-temperature band theory of ferromagnetic-antiferromagnetic interfaces including exchange anisotropy

In order to gain a microscopic understanding of ferromagnetic-antiferromagnetic (F-AF) interfaces, we have calculated the finite-temperature properties of Co/Cr superlattices using a tight-binding band-structure model and the single-site spin-fluctuation theory proposed independently by Hubbard and Hasegawa. The distribution of local magnetic moments on Co and Cr layers was determined as a function of the temperature in an eight-layer (3 Co + 5 Cr) bcc superlattice with [001] interfaces. Using these results, we performed a calculation of the temperature dependence of the exchange anisotropy constant, scrI, and the effective exchange field, ${H}_{\mathrm{ex}}$, associated with F-AF interfaces. The peculiar temperature dependence of scrI and ${H}_{\mathrm{ex}}$ arises from the nearest-neighbor interlayer exchange interaction across the F-AF interface. This interfacial exchange interaction is much smaller than the corresponding interactions in the F and AF regions. Our results account quite well for the general magnetic behavior observed in many F-AF interface systems.