Calculation of the magnetic states of cobalt overlayers on copper (111)

One- and two-atom layers of cobalt on a copper (111) surface were found to be magnetic with a spin polarization close to the bulk value. The calculation was performed in a tight-binding scheme, with single-site, full orbital interactions treated self-consistently. Antiferromagnetic and ferrimagnetic states with a two-atom periodicity were examined. A new type of "spatially modulated" state was found. The density of states and the spatial distribution of magnetization were obtained for each configuration. The ferromagnetic state was found to have the lowest total energy; the energy of the spatially modulated state was, however, calculated to be only 0.03 Ry per surface atom higher. Agreement with photoemission experiments is satisfactory: It is excellent for a one-atom layer of Co on Cu (111), but a theoretically predicted shift in peak location with Co layer thickness is not found experimentally. Calculations for both pure Cu (111) and Co on Cu (111) show that the spectral features observed at the corner of the surface Brillouin zone arise from the totally symmetric electronic states.