Coexistence of Magnetic Order and Ferroelectricity at 2D Nanosheet Interfaces

Multiferroic materials, in which the electronic polarization can be switched by a magnetic field and vice versa, are of fundamental importance for new electronic technologies. However, there exist very few single-phase materials that exhibit such cross-coupling properties at room temperature, and heterostructures with a strong magnetoelectric coupling have only been made with complex techniques. Here, we present a rational design for multiferroic materials by use of a layer-by-layer engineering of 2D nanosheets. Our approach to new multiferroic materials is the artificial construction of high-quality superlattices by interleaving ferromagnetic Ti_0.8Co_0.2O₂ nanosheets with dielectric perovskite-structured Ca₂Nb₃O₁₀ nanosheets. Such an artificial structuring allows us to engineer the interlayer coupling, and the (Ti_0.8Co_0.2O₂/Ca₂Nb₃O₁₀/Ti_0.8Co_0.2O₂) superlattices induce room-temperature ferroelectricity in the presence of the ferromagnetic order. Our technique provides a new route for tailoring artificial multiferroic materials in a highly controllable manner.