  The results of density functional theory (DFT) calculations and measurements
of X-ray photoelectron (XPS) and X-ray emission (XES) spectra of
Co-nanoparticles dispersed on graphene/Cu composites are presented. It is found
that for 0.02nm and 0.06nm Co coverage the Co atoms form islands which are
strongly oxidized under exposure at the air. For Co (2nm) coverage the upper
Co-layers is oxidized whereas the lower layers contacting with graphene is in
metallic state. Therefore Co (2 nm) coverage induces the formation of
protective oxide layer providing the ferromagnetic properties of Co
nanoparticles which can be used as spin filters in spintronics devices.
