Ultrathin Co films on flat and vicinal Cu(111) surfaces: per atom determination oforbital and spin moments

Abstract

We have performed x-ray magnetic circular dichroism, x-ray resonant magneticscattering and scanning tunnelling microscopy measurements on ultrathin Cofilms deposited on flat and vicinal Cu(111). The range of film thickness variesbetween one and 25 monolayers. For the vicinal Cu(111), Co deposition belowone monolayer leads to the formation of elongated islands preferentiallyoriented along the step edges. These islands extend over lateral lengthscales of up to several thousand ångströms. For the thicker films we stillobserve that the vicinal surface leads to the occurrence of a preferentialuniaxial growth direction. No such preferential growth direction can beidentified for the flat surface. In correlation to the Co growth we observean increase of both the orbital and the spin moment per Co atom onvicinal Cu(111) of about 25% versus what was observed for Co on flatCu(111). This enhancement is observed in both the x-ray absorption and thereflectivity measurements. Similar to what was earlier reported for Co onCu(100) we also observe for the case Co on Cu(111) an increase in the ratioml /ms(orbital to spin moments) of 40% for thin Co films. In contrast to what has beenreported for Co films on flat and vicinal Cu(100) we do not observe any majorvariations in the occupancy of the Co 3d states for Co grown on the vicinalCu(111) surface.