Giant Magnetoelectric Coupling in Asymmetric Ferromagnet-Ferroelectric-Metal Trilayers: Toward Electric Control of Magnetization

By examining electron screening at the surface of ferromagnetic metals and semiconductors, we propose an asymmetric ferromagnet-ferroelectric-metal trilayer to realize giant magnetoelectric effect. The origin is the strengthened accumulation of spin-polarized screening electrons at the ferromagnet-ferroelectric interface. Including the electrostatic energy from such spin-polarized charges in the Laudau-Devibshire free energy for ferroelectics, a magnetoelectric coupling term $\chi P^2M^2$ is derived, and consequently an electric control of magnetization hysteries is observed. The dependence of $\chi$ as well as the ME effect on the choice of materials is discussed for some real ferromagnets.