Dependence of Exchange Coupling on Interfacial Conditions in SmCo₅/Co System: A First-Principles Study

We have performed first-principles calculations to study the interfacial exchange coupling in a SmCo₅/Co multilayer model system. The hard phase hcp SmCo₅ and the soft phase hcp Co (or Co_1–x Fe _x ) stacking along (101^-0) direction are structurally well matched. The atomic structure, including the alignment and the separation between layers, were optimized first. Then the non-collinear magnetic structures were calculated to explore the exchange coupling dependence on the variation of the atomic composition across the interface. We found that the inter-phase exchange coupling strength is strongly dependent on the interface condition between the hard and soft phase by comparing the exchange coupling strengths in different interface conditions. The findings were further confirmed by the calculated site-to-site exchange parameters across the interface.