Altering the Gd(0001) surface electronic structure with hydrogen adsorption

Hydrogen adsorption on Gd(0001) has been studied with angle-resolved photoemission. Hydrogen adsorption attenuates the surface state near ${\mathit{E}}_{\mathit{F}}$ on the clean Gd(0001) surfaces and induces two two-dimensional bands which are at 3.8 eV and about 6 eV near Γ¯. The state with the smaller binding energy has ${\mathit{d}}_{\mathit{z}}^2$ character at Γ¯ and disperses away from ${\mathit{E}}_{\mathit{F}}$ about 1 eV. The state at the greater binding energy disperses toward ${\mathit{E}}_{\mathit{F}}$ about 0.5–1 eV. At low substrate temperatures (120–130 K), the hydrogen chemisorption on the Gd(0001) surface results in a work-function decrease of 0.2 eV. The correlation between the changes of the surface electronic structure and the corresponding change in the surface magnetic ordering is discussed.