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

Abstract

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 °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 °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 α_ME maxima dependent on the H_dc field sweep direction. The sample with x = 0.4 exhibits the highest maximum α_ME of 420 μV Oe⁻¹ cm⁻¹.