Exchange coupling between ferro- and antiferromagnetic layers across a non-magneticinterlayer: Co/Cu/FeMn on Cu(001)

Abstract

The as-grown magnetic domain patterns of epitaxial single-crystalline Co/FeMn bilayersand Co/Cu/FeMn trilayers were investigated by magnetic circular dichroism domainimaging using a photoelectron emission microscope. Small domains were observed when Cowas deposited directly on top of antiferromagnetic FeMn films. On inserting a Cu spacerlayer between the ferromagnetic Co layer and the antiferromagnetic FeMn layer, theas-grown domain size increases continuously with increasing Cu layer thickness, which isattributed to the decrease of the interlayer exchange coupling between the Co and FeMnlayers. Domain images of the Co layer acquired after applying different external magneticfields confirm the relation between as-grown domain size and interface coupling to theantiferromagnetic FeMn layer across the non-magnetic Cu spacer layer. It is found that afield of 44 Oe is sufficient to annihilate most small domains in the area where Co andFeMn are coupled through the Cu wedge, while it has no effect on the domainconfiguration of a Co/FeMn bilayer. By analysing the dependence of the average domainsize of the Co layer on the Cu thickness in terms of interface coupling betweenthe Co and FeMn layers across the Cu layer, the apparent estimated couplingenergy was found to be different for different Co thickness. This is ascribed tokinetic barriers hindering the formation of larger domains from smaller ones.