Magnetoelectric effect in functionalized few-layer graphene

We show that the spin moment induced by sp3-type defects created by different covalent functionalizations on a few-layer graphene structure can be controlled by an external electric field. Based on ab initio density functional calculations, including van der Waals interactions, we find that this effect has a dependence on the number of stacked layers and concentration of point defects, but the interplay of both with the electric field drives the system to a half-metallic state. The calculated magnetoelectric coefficient α has a value comparable to those found for ferromagnetic thin films (e.g., Fe, Co, Ni) and magnetoelectric surfaces (e.g., CrO2). The value of α also agrees with the universal value predicted for ferromagnetic half-metals and also points to a novel route to induce half-metallicity in graphene using surface decoration.