Magnetoelectronic instability of graphene on a ferromagnetic substrate

The features of graphene on a ferromagnetic substrate are theoretically studied. It is demonstrated that such a system exhibits an unstable electronic state at low temperatures. Namely, under certain conditions, the perfect uniform ferromagnetic polarization becomes spontaneously broken toward the formation of a canted state. Canting in the substrate gives rise to the band gap opening in the single-electron spectrum of graphene. The width of this gap is calculated, and the conditions necessary for the observation of such instability in the experiment are discussed.