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 H-dc, 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. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.