Surface magnetism of iron films following the adsorption of oxygen: a comparison between Fe/Ag(100) and Fe/MgO(100)

The correlation between crystallographic order and surface magnetism has been investigated by studying the chemisorption of oxygen on iron films grown on Ag(100) and MgO(100). The exchange splitting of O2p states depends strongly on surface order as it decreases from Delta E-O2p similar or equal to 0.5 eV for the O(1x1) phase to Delta E-O2p similar or equal to 0.2 eV for the O/Fe/MgO disordered phase. Even smaller values of Delta E-O2p are obtained for the highly disordered O/Fe/Ag system, demonstrating that the coupling of oxygen states with the magnetic film underneath is strongly affected by crystallographic order.