Electric-field control of magnetism in graphene on chromia

First-principle calculations are used to investigate how an external electric field controls the spin polarization in graphene on chromia, a system of interest in the area of spin field-effect transistors. Both free-standing chromia thin films and graphene-bilayers are considered. The effect of the electric field depends on the thickness of the chromia and ranges from moderately strong and linear effects to very strong nonlinear magnetoelectricity. The graphene modifies and generally enhances the nonlinear magnetoelectric effect. We also find that the external electric field drastically changes the energy-dependent spin polarization in the graphene layers, which is predicted to reach values of up to about 80%.