MAGNETIC COUPLING OF NI, CU AND CO BILAYERS 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) subst rate were investigated. The Co layers were about 2 monolayers (Mi,) an d the Ni layers were between 1.5 and 4.5 ML thick. It was observed tha t, for Co/Ni bilayers, the entire system has only one Curie temperatur e, T-C. After having been covered by 2-7 ML Cu, Ni and Co films exhibi t a significantly lower T-C. For trilayers, different Curie temperatur es 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 a nd antiferromagnetic, depending on the spacer thickness and the order of the layers.