Dielectric and magnetic properties of bulk and layered tape cast CoFe2O4–Pb(Fe1/2Ta1/2)O3 composites

The microstructure, dielectric and magnetic properties of bulk and layered CoFe2O4–Pb(Fe1/2Ta1/2)O3 composites were studied. Ceramic samples based on previously mixed ferrite and relaxor powders were sintered at 950 °C. Ferrite and relaxor green tapes 150 μm thick were prepared by tape casting, then cut, stacked alternately, laminated and co-sintered at 950 °C. High and broad maxima of dielectric permittivity reaching 2000 at 1 kHz were found for bulk CoFe2O4–Pb(Fe1/2Ta1/2)O3 ceramic. Measurements of the magnetization of the investigated composites as a function of magnetic field and temperature exhibited behavior typical of hard magnetic materials. The layered composites showed lower coercivity, higher saturation magnetization and a higher magnetoelectric coefficient than the bulk ceramics. Distinct changes in field- and zero field-cooled magnetization curves at −200 °C could be ascribed to the antiferromagnetic transition of the PFT relaxor phase. Multilayer CoFe2O4–Pb(Fe1/2Ta1/2)O3 composites exhibited a magnetoelectric coefficient of 200 mV/(cm Oe) at a frequency of the modulation magnetic field equal to 5 kHz.