Spin-Polarized Semiconducting Band Structure of Monolayer Graphene on Ni(111)

The magnetic properties of graphene have attracted much attention for more than a decade. Recent studies have shown that adatoms or atomic vacancies in graphene could exhibit localized magnetic moments. However, a macroscopic spin-polarized semiconducting band structure has never been experimentally realized in graphene. Here, we demonstrate that a graphene monolayer, hybridized with an underlying Ni(111) substrate, exhibits a spin-polarized semiconducting state even at room temperature. Our spin-polarized scanning tunneling microscopy (STM) experiments, complemented by first-principles calculations, explicitly demonstrate that the interaction between graphene and the Ni substrate generates a large gap in graphene and simultaneously leads to a relative shift between majority- and minority-spin bands. Consequently, the graphene sheet on the Ni substrate exhibits a spin-polarized gap with an energy of several tens of meV even at room temperature.