Field-effect-driven half-metallic multilayer graphene

The realization of modern spintronic devices requires injection of spin-polarized currents. Materials of choice for such devices are half-metals, namely compounds conducting in one spin channel and insulating in the other, like Heussler alloys and some transition metal oxides. Here, by using first-principles calculations, we show that field-effect doping of graphene multilayers with rhombohedral stacking induces a perfect half-metallic behaviour with 100% of spin current polarization already at dopings attainable in conventional field effect transistors with solid state dielectrics. Our work defines a new kind of spintronic devices where the spin state is selected and driven by electric fields.