Exchange-Split Adsorbate Bands: The Role of Substrate Hybridization

Abstract

Spin-split adsorbate-induced bands have been observed for $p(1\mathrm{}\times 1)$ oxygen and $c(2\mathrm{}\times 2)$ sulfur on Fe(100) by use of spin-polarized angle-resolved photoemission. For the $p_z$-symmetry orbitals, the exchange splitting is considerably larger at the Brillouin-zone center (1.3 eV for O, 0.5 eV for S) than at the zone edge (0.25 and 0.2 eV, respectively). This is attributed to enhanced hybridization with substrate $d_z^{}{}_{}{}^2$ orbitals when the adsorbate $p_z$ band overlaps the bulk continuum. Our observation of an exchange splitting provides evidence of a small magnetic moment on the adsorbate atoms. Our results also indicate that the adsorbate layer is ferromagnetically aligned with the substrate.