Visualization of the Exchange Bias Effect in an FeMn/Co Heterostructure via Photoemission Electron Microscopy

The magnetic domains in a heterostructured film consisting of antiferromagnetic FeMn and ferromagnetic Co layers were investigated via photoemission electron microscopy combined with X-ray magnetic circular dichroism (XMCD-PEEM) under various magnetization and heat-treatment conditions. Further, these domains were visualized in the macroscopically exchange-biased state after the field-cooling process. By further heating the film above the Neel temperature of FeMn, followed by cooling, it was assumed that the sublattice magnetization of the antiferromagnet (AFM), FeMn, which was restored from the paramagnetic state, aligned submissively according to the existing domain structure of the adjacent ferromagnet (FM), Co, without disturbing its domain structure. Such flexibility of the magnetization of the AFM to the magnetic domains of the neighboring FM during the magnetization from the paramagnetic state contradicts the well-known property of the AFM, i.e., robustness against the external magnetic field, following the determination of its magnetization directions.