Electron correlation and charge transfer at the Ni/Co interface

Abstract

The evolving magnetism and electronic structure at the Ni/Co interface have been studied using x-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy (XPS) with circularly polarized x rays. Deposition of ultrathin Ni films on thin films of Co grown on Cu(001) results in an intensity enhancement across the Co L2.3 absorption edge. By comparison, the intensity of the Ni L2.3 edge decreases as a function of Ni film thickness. The relative changes in the Ni and Co XAS intensities are interpreted as an electronic charge transfer from the Co to the Ni. Distinct changes in the Co 2p XAS and XPS line shapes after addition of the Ni overlayer imply a modification of the Co 3d electron correlation due to the charge transfer. The change in the electronic structure is related to the interface magnetism using magnetic circular dichroism sum rule analysis.