X-ray magnetic circular dichroism study of spin reorientation transitions of magnetic thin films induced by surface chemisorption

Spin reorientation transitions of Co and Ni thin films induced by surface chemisorption have been investigated for CO-adsorbed Co/Pd(111) and CO- and H-adsorbed Ni/Cu(001) by means of Co LIII,II- and Ni LIII,II-edge x-ray magnetic circular dichroism (XMCD). For four to six monolayer (ML) Co/Pd(111), a spin reorientation transition from surface parallel to perpendicular magnetization has been observed at 200 K after CO dosage. The region of perpendicular magnetic anisotropy (PMA) becomes about 3 ML thicker at this temperature. For Ni/Cu(001), similar transitions have been confirmed when the layers are covered with CO or H, and the PMA range is also expanded, in this case by about 2 ML. The observed stabilization of perpendicular magnetic anisotropy due to chemisorption is ascribed to quenching of the surface parallel magnetic orbital moment. The effects of the fashion in which adsorption occurs on the easy axis of thin-film magnetization are also examined by comparing the differences in behavior between CO- and H-adsorbed Ni films.