Magnetism at the Ni(001) surface: A high-precision, all-electron local-spin-density-functional study

We present the results of high-precision, all-electron, self-consistent local-spin-density-functional calculations on a seven-layer Ni(001) film using the full-potential linearized-augmented-plane-wave method. It is found that the surface atoms have a magnetic moment which is enhanced by almost 20% compared with the bulklike atoms in the interior of the film. There is no indication of a Friedel-type oscillation in the layer-by-layer magnetic moments. Although the negative core-contact spin densities for the surface atoms are enhanced in magnitude by 20%, the contribution from the (4s-derived) valence electrons changes sign and becomes slightly positive in the surface layer. This causes a net decrease in magnitude of the total contact spin density by 20%. In agreement with photoemission experiments we find the majority-spin M»3 surface state to be occupied, contrary to the early results of Wang and Freeman for a nine-layer film and to recently presented results obtained by Jepsen et al. on a five-layer film. The work function is found to be 5.37 eV, in good agreement with the experimental value of 5.22 0.04 eV. For the core levels of the surface atoms we obtain a shift between 0.3 and 0.5 eV towards reduced binding energies which is explained in terms of d-band narrowing and layer-by-layer charge neutrality.