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/Ba_0.6Sr_0.4TiO₃(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.