Enhancement of charge-mediated magnetoelectric coupling in Fe 3 O 4 /SrTiO 3 /Ba 0.6 Sr 0.4 TiO 3 heterostructure.

The in-plane magnetic hysteresis loops of Fe3O4/SrTiO3(STO) and Fe3O4/STO/Ba0.6Sr0.4TiO3(BSTO) heterostructures have been investigated at 200 K under various electric fields. The bottom BSTO layer of the STO/BSTO bilayer is used to improve the dielectric properties of the top STO layer. The polarization of the STO/BSTO bilayer is ~78% larger than that of the STO layer at room temperature due to the improvement of surface topography and the contribution of electrostatic interlayer coupling. A significant enlargement (~70%) in the magnetoelectric response of Fe3O4/STO/BSTO heterostructure has been achieved at 200 K and 300 kV cm-1 after introducing the BSTO layer, since the STO/BSTO bilayer with larger dielectric constant supplies more polarization charges at its interface to the Fe3O4 layer than the STO layer. It indicates that the dielectric bilayer improves the polarization and thus benefits the magnetoelectric coupling in the multiferroic heterostructure.