First-principles study of the structural and magnetic properties of graphene on a Fe/Ni(111) surface

The structure and spin-resolved electronic states of a graphene-adsorbed Fe/Ni(1 1 1) surface are investigated and compared with a graphene/Ni(1 1 1) surface using first-principles calculations. Nine possible geometries are studied with Fe and C atoms at different sites with respect to the topmost Ni atoms. Geometries with one C atom located on top of an Fe atom (C1) and one at a hollow (fcc or hcp) site (C2) are the most energetically favourable. The electronic states of graphene are significantly modified by the interaction with the Fe/Ni(1 1 1) surface. The dominant pi states of the C2 atom are drastically shifted towards the Fermi level and become highly positive-spin-polarized due to the corresponding spin-down states located above the Fermi level. The level shift is very small for the spin-up pi states of the C1 atom but obvious for the spin-down states due to spin splitting induced by Fe atoms, resulting in a negative spin polarization at shallow levels and a positive one at deeper levels. The adsorption of graphene on Fe/Ni(1 1 1) is stronger than that on the clean Ni(1 1 1) surface.