All-electron study of c(2×2) S chemisorbed above magnetic Fe(001)

Abstract

We have performed a first-principles study of the adsorption of sulfur above a magnetic Fe surface. Our results, derived from the all-electron, film full-potential augmented-plane-wave method applied to a seven-layer Fe film with and without c(2×2) overlayers of S, include determinations of the equilibrium sulfur height (heq) and vibrational frequency, as well as the associated electronic and magnetic structures. We find excellent agreement between our calculated value (1.12 Å) of heq with the earlier result (1.09±0.05 Å) derived by Legg et al. from a dynamical low-energy electron diffraction intensity analysis. The adsorption induces antibonding minority surface states immediately above and below EF which play an important role both in reducing the magnetic moment of the surface Fe atom (by ∼20%) and in the resulting calculated increase (0.86 eV) in work function. These states should be clearly resolvable in both integrated and angle-resolved spin-polarized photoemission and inverse-photoemission experiments. We present additional predictions, including the adsorption-induced changes in the hyperfine fields.