Hysteretic magnetoelectric behavior of CoFe2O4-BaTiO3 composites prepared by reductive sintering and reoxidation

Magnetoelectric composites (CoFe2O4)(x)-(BaTiO3)(1-x) with x = 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by a polyol mediated synthesis route. The densification step was performed in a reducing forming gas atmosphere at 1250 degrees C. Under these conditions Co2+ and Fe3+ are reduced to the corresponding metals and thus a reaction of these elements with the BaTiO3 matrix is prevented. Reoxidation in air to CoFe2O4 at a rather low temperature of 800 degrees C leads to samples free of secondary phases. While the course of the synthesis was monitored by TGA, XRD and photometric analysis, the final composites were characterized via SEM, EDX, impedance spectroscopy and magnetic and magnetoelectric (ME) measurements. All samples show pronounced ME hystereses and alpha ME maxima dependent on the H-dc field sweep direction. The sample with x = 0.4 exhibits the highest maximum alpha ME of 420 mu V Oe(-1) cm(-1).