Surface structural and magnetic properties of cobalt bilayer deposited on Pt(111) with Ni buffer layer

A cobalt bilayer film was deposited on a monolayer (ML) Ni/Pt(111) surface at room temperature. The dependencies of the structural and magnetic properties of the surface on the annealing temperature were investigated. During the annealing, it was found that the formation of Co-Ni alloy occurs before the formation of Co-Ni-Pt alloy. After high-temperature annealing, the surface consisted of Co-Ni-Pt alloys with a Pt-rich phase. We found that the perpendicular magnetic anisotropy (PMA) contribution of the Co-Ni-Pt alloy at the surface was greater than that of the Co-Pt alloy below. The ultraviolet photoelectron spectrum (UPS) of the 2ML Co/1ML Ni/Pt(111) system showed a redistribution of electron density on the surface after annealing. The UPS peak height near the Fermi edge was mostly dependent on the surface composition. However, the change in the work function was not dependent on the PMA after high-temperature annealing. The strength of the PMA of this system can be tuned to a desired level by annealing without affecting the work function.