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Ferromagnetic films evaporated at oblique incidence show invariably an uniaxial in-plane magnetic anisotropy component with easy axis perpendicular to the incidence plane. Scanning Tunneling Microscopy (STM) images reveal that oblique deposition results in rough films with highly anisotropic correlation functions of the surface profile. We show that simple shape anisotropy calculations using high-quality STM roughness data as input reproduce the measured anisotropies remarkably well and unambiguously relate them to the long-ranged dipolar interactions.

The two-dimensional band structure of a single epitaxial ErSi2 layer on Si(111)is calculated by means of the crystalline extension of the extended Hiickel method for various atomic structures and tested against experimental bands determined by angle-resolved photoemission. In particular, adopting for the silicide layer the structure proposed in previous work, i.e. , a hexagonal Er monolayer underneath a buckled Si top layer, various possible interfacial geometries are investigated, namely with the Er in top, substitutional, T4, and H3 sites of the Si(111)substrate and for the two possible orientations of the latter with respect to the buckled Si top layer. With the exception of the substitutional site, all models show two characteristic bands near the Fermi level that are essentially full and empty, respectively, as observed experimentally.Yet, the topology of these bands is correctly reproduced for only two interfacial geometries, namely Er in H3 (T4) sites with the buckled Si top layer having an orientation identical (opposite) to the substrate Si double layers. For both models the overall agreement between calculated and experimental bands is quite satisfactory. The prominent almost-filled band observed experimentally in the 0 -1.7-eV binding-energy range mainly derives from the dangling bonds of the buckled Si top layer, but shows a strong hybridization with Er 5d states near the center of the surface Brillouin zone.

The surface electronic structure of epitaxial &3 X &38.30 ErSi& 7 layers on Si(111)has been studied by high-resolution angle-resolved ultraviolet photoemission spectroscopy. Typical surface states or resonances are unambiguously identified and their band dispersions mapped along the high-symmetry I M, I I(, and E M lines of the (1 X 1) surface Brillouin zone. These data are compared to the band structure of two-dimensional p (1 X 1) Er silicide extensively studied in previous works. It is found that the prominent surface bands observed in the 0 -3-eV binding-energy range can be readily derived from the p(1X 1) surface-silicide bands folded back into the reduced &3 X &3 zone. This indicates that the bulk silicide is also terminated with a buckled Si layer without vacancies, quite similar to the surface-silicide termination. In particular, specific surface bands reflect the doubly (essentially) occupied dangling bonds and the back bonds of the buckled Si top layer.

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