Surface magnetism during the early stages of oxygen-assisted growth of Cr on Fe(001): a SPMDS study

The surface magnetic properties of ultrathin Cr films grown on O(1 x 1)-Fe(0 0 1) have been studied by means of spin-polarised metastable de-excitation spectroscopy (SPMDS). The spin-selected surface density of states extracted from the experimental SPMDS data provides information on both composition and magnetic properties of the topmost layer. We find that oxygen floats on the surface of the growing Cr film and that Cr/Fe intermixing is restricted to the first Cr layer. Concerning the magnetic properties, a strong polarisation of Cr-3d electrons is found in agreement with theoretical calculations. Oxygen 2p states are polarised too and their polarisation is opposite to that of Cr3d states. Surface magnetisation as a function of the Cr film thickness shows an oscillatory behaviour induced by the layered antiferromagnetic structure of Cr. At variance with the results of other experimental investigation in this case the layered antiferromagnetic structure of Cr is already present in the 3 ML thick film.