Interface effects at a half-metal/ferroelectric junction

Magnetoelectric effects are investigated ab-initio at the interface between half-metallic and ferroelectric prototypes: Heusler Co$_2$MnSi and perovskite BaTiO$_3$. For the Co-termination ferroelectricity develops in BaTiO$_3$ down to nanometer thicknesses, whereas for the MnSi-termination a paraelectric and a ferroelectric state energetically compete, calling for a full experimental control over the junction atomic configuration whenever a ferroelectric barrier is needed. Switch of the electric polarization largely affects magnetism in Co$_2$MnSi, with magnetoelectric coupling due to electronic hybridization at the MnSi termination and to structural effects at the Co-termination. Half-metallicity is lost at the interface, but recovered already in the subsurface layer.