Induced magnetization in Cu atoms at the Fe-Co/Cu3Au(001) interface: X-ray magnetic circular dichroism experiments and theoretical results

Abstract

The induced magnetization in Cu atoms at the interface between ferromagnetic (FM) Fe/Co ultrathin films and a nonmagnetic (NM) Cu3Au(001) substrate was explored by the investigation of two structures of five alternated Fe and Co monoatomic layers with different stacking orders with a Fe or a Co layer in direct contact with the Cu3Au(001) surface. First principles calculations were applied to disentangle the origin of magnetic proximity effects at these FM/NM interfaces. The hybridization between the electronic states of the FM layers, resulting in a pronounced widening of the d-bands of the local density of states of Fe-Co interface atoms, has a fundamental effect in the spin-polarization of the NM substrate. X-ray magnetic circular dichroism measurements at the L2,3-edges of Fe, Co and Cu allowed to extract the spin and orbital magnetic moments of Fe and Co, and to measure extremely low magnetic moments induced in Cu atoms. It is shown that the magnetism is induced only in the Cu and Au atoms at the first CuAu monolayer at the very surface of the substrate, i.e., the Cu XMCD signal is due to only 0.5 ML magnetic Cu atoms.