Nanoparticle-Based Magnetoelectric BaTiO3-CoFe2O4 Thin Film Heterostructures for Voltage Control of Magnetism

Multiferroic composite materials combining ferroelectric and ferromagnetic order at room temperature have great potential for emerging applications such as four-state memories, magnetoelectric sensors, and microwave devices. In this paper, we report an effective and facile liquid phase deposition route to create multiferroic composite thin films involving the spin-coating of nanoparticle dispersions of BaTiO3, a well-known ferroelectric, and CoFe2O4, a highly magnetostrictive material. This approach offers great flexibility in terms of accessible film configurations (co-dispersed as well as layered films), thicknesses (from 100 nm to several mu m) and composition (5-50 wt % CoFe2O4 with respect to BaTiO3) to address various potential applications. A detailed structural characterization proves that BaTiO3 and CoFe2O4 remain phase-separated with clear interfaces on the nanoscale after heat treatment, while electrical and magnetic studies indicate the simultaneous presence of both ferroelectric and ferromagnetic order. Furthermore, coupling between these orders within the films is demonstrated with voltage control of the magnetism at ambient temperatures.