Efficient spin injection in graphene using electron optics

We investigate theoretically spin injection efficiency from the ferromagnetic graphene to normal graphene (FG/NG) based on electron optics, where the magnetization in the FG is assumed from the magnetic proximity effect. Based on a graphene lattice model, we demonstrated that one spin-species electron flow from a point source could be nearly suppressed through the FG-NG interface, when the total internal reflection effect occurs with the help of an additional barrier masking the Klein tunneling, while the opposite spin-species electron flow could even be collimated due to the negative refraction under suitable parameters. Not only at the focusing point is the efficient spin injection achieved, but in the whole NG region the spin injection efficiency can also be maintained at a high level. It is also shown that the nonideal FG-NG interface could reduce the spin injection efficiency since the electron optics phenomena are weakened owing to the interfacial backscattering. Our findings may shed light on making graphene-based spin devices in the spintronics field. DOI: 10.1103/PhysRevB.86.245413