Multiferroic properties of multilayered BaTiO3–CoFe2O4 composites via tape casting method
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Multiferroic magnetoelectric (ME) BaTiO3–CoFe2O4 (BTO–CFO) ceramic composites with different thicknesses were fabricated via tape casting technique. The interfacial morphology of the composite demonstrates the presence of plate-like grains with a thickness of ~400 nm. This could be associated with the residual stresses originated from lattice mismatch and different thermal expansion coefficients between BTO and CFO layers. The dielectric constant, piezoelectric constant, and ferroelectric properties of the multilayered composite are degraded in the presence of CFO layers in comparison with those of BTO bulk. Furthermore, the dielectric constant and polarization of the composite decrease with increasing frequency. The leakage current density and magnetic remanence ratio of the composite reach up to the order of 10−6 A/cm2 and 40 %, respectively. The direct and converse ME coefficients were measured to be 8.1 μV/cm Oe and 1.1 × 10−3 G/V, respectively. Based on the converse ME effect, an electrically controlled ME inductor was designed using the composite as its core. The inductance and tunability of the inductor increase with increase of applied dc electric field.
KeywordsCoFe2O4 Leakage Current Density Piezoelectric Constant Interfacial Coupling Multilayered Composite
The authors would like to thank National Natural Science Foundation of China (Grant No. 60871017/f010612) and Provincial Nature Science Foundation of Hubei in China. The authors also acknowledge the support of Shaanxi Normal University and Tsinghua University for the CME and DME coefficients measurement, respectively.