Thin Co films on Cu(111) studied by electron capture spectroscopy

Abstract

We have studied thin films of Co on Cu(111) single crystals with electron capture spectroscopy (ECS). The magnetism from the cobalt layer can be detected clearly in remanence and as a function of the outer magnetic field. The measured circular polarization of the emitted light is related directly to the structural and magnetic changes of the system, depending on the cobalt layer thickness. We find the set-in of in-plane magnetization at ∼2 monolayers of cobalt and the saturation of our signal at a film thickness of 7-8 monolayers. At coverages above 3-4 monolayers the increasing growth of hcp cobalt domains at the expense of fcc cobalt domains gives rise to a linearly increasing ECS signal up to 7.5 monolayers. We attribute this to the fact that the fcc cobalt domains are covered with copper, whereas the hcp cobalt domains expose cobalt in the upper layer. Monte-Carlo simulations of our ion scattering experiments show that great experimental care has to be taken in order to avoid excessive sputtering damage to the sample. By using moderate primary ion energies and small angles of incidence, thin films can be investigated with ECS in the grazing incidence geometry without changing the film structure.