Magnetic interface coupling in single-crystalline Co/FeMn bilayers

The magnetic coupling between epitaxial single-crystalline Co and FeMn layers on Cu(001) was investigated by element-resolved magnetic circular dichroism domain imaging using a photoelectron emission microscope. As-grown Co domain patterns reveal the presence of many small domains in the antiferromagnet. The coupling of the Co layer is found to be along <100> crystallographic directions. This is discussed in terms of a 45degrees coupling due to frustrations at topological 90degrees domains in the FeMn layer. Coercivity oscillations as a function of FeMn thickness with atomic monolayer period support the importance of such step-induced domains in the coupling.