Surface magnetism of an ultrathin Fe/Ag(100) film: Influence of O2 and CO adsorption

The influence of adsorption of O2 and CO on the surface magnetism of a 10 ML film of Fe grown at 120 K on Ag(100) has been investigated by spin polarized metastable deexcitation spectroscopy. The extreme surface sensitivity of this spectroscopy allows us to study the effects of adsorption from exposures as low as similar to 0.1 L. Oxygen adsorbs dissociatively at 120 K and the O-2p states are spin polarized. At this low temperature, oxidation starts from exposures of the order of 1 L and above 3-4 L a non-magnetic oxide layer is formed. CO adsorbs molecularly at T = 120 K and then dissociates above room temperature. Following dissociation, carbon atoms do not have any effect on the spin polarization of oxygen and iron states at the surface.