CHEMISORPTION-INDUCED CHANGE IN THIN-FILM SPIN ANISOTROPY - OXYGEN-ADSORPTION ON THE P(1 X 1)FE/AG(100) SYSTEM

Magneto-optical techniques are used to explore the magnetic anisotropy of ultrathin (1-3 monolayer) epitaxial Fe films on Ag(100) when exposed to oxygen. Small doses of oxygen produce striking changes in the spin anisotropy of bilayer magnetic films: the preferred spin orientation changes from perpendicular to the surface to an in-plane orientation. Low-energy electron-diffraction analysis indicates the oxygen adsorption is accompanied by significant structural changes in the film. The structural changes are consistent with recently observed effects of adsorbed gases on metal epitaxy. While some of the observed effects can be reconciled with the established thickness dependence of thin-Fe-film magnetic properties by assuming oxygen-induced quenching, and taking into account the structural changes of the film that accompany oxygen adsorption, the primary effect (oxygen-induced change of preferred spin direction) appears to be produced by electronic effects that govern the surface-anisotropy parameter. Previous disagreements between results obtained by spin-polarized photoemission and magneto-optical techniques are resolved.