Magnetoelectric coupling on multiferroic cobalt ferrite–barium titanate ceramic composites with different connectivity schemes

In this article we report on the synthesis and multiferroic properties of cobalt ferrite (CoFe2O4)–barium titanate (BaTiO3) biphasic composites. The initial composite nanopowder was synthesized by a combination of co-precipitation and organosol methods. A ceramic sample with (3–0) connectivity, i.e. BaTiO3 grains in a CoFe2O4 matrix was obtained by a combination of spark plasma sintering and annealing. In order to understand the correlations between morphology, electric properties, and magnetization, we present a detailed study at different preparation steps and compare it to the properties of a conventionally sintered sample with the traditional (0–3) connectivity, i.e. CoFe2O4 grains in a BaTiO3 matrix. We observe that the (3–0) sample shows improved magnetic properties in comparison to the conventionally sintered composite of the same composition. In spite of relatively large leakage current for the (3–0) sample compared to the traditional (0–3) one, it exhibits a converse magnetoelectric effect that follows the Hdc dependence of the piezomagnetic coefficient. The magnetic field-dependence of electric polarization at the surface was investigated utilizing X-ray absorption spectroscopy and its associated linear and circular dichroisms.