Angle-resolved photoemission of orderedPb∕Ni(111)surface phases

Abstract

$\mathrm{Pb}∕\mathrm{Ni}(111)$ surface phases were investigated by angle-resolved photoemission spectroscopy. Annealing of the $\mathrm{Pb}∕\mathrm{Ni}(111)$ surface led to the formation of the $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ reconstruction characterized by a topmost layer consisting of a substitutional alloy. The transformation to the $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ structure was accompanied by a modification of the surface band structure confirming the formation of a new phase in the Ni(111) surface layer, characterized by a transformation from ferromagnetic to a nonmagnetic state. The modification was displayed as a disappearance of the $\mathbit{k}$-dependent exchange splitting in the topmost alloy layer that was observed on the clean Ni surface due to the energy difference between spin-up and spin-down states. Fermi surface mapping showed partial disappearance of splitting of bands crossing the Fermi level.