Magnetic coupling of Ni, Cu and Co bi- and trilayers probed by magnetic circular X-ray dichroism

Using magnetic circular X-ray dichroism (MCXD), Co/Ni, Cu/Co and Cu/Ni bilayers and Co/Cu/Ni and Ni/Cu/Co trilayers grown on a Cu(001) substrate were investigated. The Co layers were about 2 monolayers (ML) and the Ni layers were between 1.5 and 4.5 ML thick. It was observed that, for Co/Ni bilayers, the entire system has only one Curie temperature, T c . After having been covered by 2-7 ML Cu, Ni and Co films exhibit a significantly lower Tc. For trilayers, different Curie temperatures were determined for Ni and Co when separated by a 2-6 ML Cu spacer. The coupling of Ni and Co layers was found to be both ferromagnetic and antiferromagnetic, depending on the spacer thickness and the order of the layers.