MAGNETIC SURFACE-STATE BECOMES NONMAGNETIC BY OXYGEN-ADSORPTION

The influence of oxygen adsorption on a partly occupied spin-split sur face state at Ni(111) has been studied by spin-resolved inverse photoe mission. With increasing oxygen exposure the surface state shifts to h igher energy, thereby becoming totally unoccupied and no longer contri buting to the surface magnetic moment. Moreover, its exchange splittin g of about 100 meV on the clean surface is reduced to less than 25 meV for the ordered p(2x2) oxygen overlayer, whereas the splitting of an sp bulk band transition remains unaffected. The data demonstrate on a microscopic level the oxygen-induced reduction of the magnetic moment at the surface of Ni(111).