Effect of adsorbates on the spin-polarized photoemission of itinerant ferromagnets

Abstract

The adsorbate systems O(2×1)/Ni(110), S c(2×2)/Ni(110), and O p(2×2)/Fe(110) were investigated by means of spin-, angle-, and energy-resolved photoemission spectroscopy. For the Ni 3d bands with $S_4$ symmetry near the X point of the Brillouin zone we find no change of the exchange splitting due to adsorption of O and S. A majority-spin band with $S_3$ symmetry at the same k point shows a slight shift to lower binding energies under adsorption of O. For O p(2×2)/Fe(110) no changes in binding energy were observed for the Fe d bands with ${\Sigma }_1^{\downarrow }$ and ${\Sigma }_4^{\uparrow }$ symmetry. Depolarization effects of the photoelectrons caused by the adsorbates are interpreted in terms of exchange scattering processes. The same scattering process gives rise to very pronounced structures in the spin-resolved spectra of S c(2×2)/Ni(110). Different scattering probabilities for majority and minority electrons indicate that O and S on Ni(110) are polarized parallel to the Ni bulk spin polarization.