To obtain a larger spin signal for use in graphene-based spintronic devices, the spin injection efficiency needs to be enhanced. Previously researchers can increase the efficiency by inserting a tunnel barrier such as Al2O3or MgO between ferromagnet and graphene. However, the key value in spin transport is still very low because of the conductance mismatch as well as the limit to fabricate a high-quality tunnel barrier at the junction surface. Here we use a highly spin-polarized ferromagnetic material—Heusler alloy Co2MnGe as a substitutional scheme without the tunnel barrier. The spin injection efficiency of our Co2MnGe (111)/graphene junction can be as high as 73% which is much higher than 1% of ferromagnet/graphene or 30% of ferromagnet/oxide/graphene using first-principles study. The large spin polarization can be explicated by analyzing the transmission spectrum at the nonequilibrium state.
Spin injection into multilayer graphene from highly spin-polarized Co2FeSi Heusler alloy
