Controllable spin transport in ferromagnetic graphene junctions

We study spin transport in normal/ferromagnetic/normal graphene junctions where a gate electrode is attached to the ferromagnetic graphene. We find that, due to the exchange field of the ferromagnetic graphene, spin current through the junctions has an oscillatory behavior with respect to the chemical potential in the ferromagnetic graphene, which can be tuned by the gate voltage. In particular, we obtain a spin current reversal controllable by the gate voltage. Our prediction of high controllability of spin transport in ferromagnetic graphene junctions may contribute to the development of spintronics.