Ferroelectric and magneto-dielectric properties of yttrium doped BaTiO3-CoFe2O4 multiferroic composite

Multiferroic composites of ferroelectric and ferrite phases having general formula xCoY(0.1)Fe(1.9)O(4)(1-x) Ba0.95Y0.05TiO3 (where x=0.05, 0.1 and 0.15) were prepared using the conventional solid-state reaction method. X-ray diffraction studies were done to confirm the presence of constituent phases. The microstructural analysis revealed an increase in density with the increase of ferrite content in the ferroelectric matrix. Dielectric studies of the composites, in the temperature range 100-550K revealed two ferroelectric phase transitions. Variation of dielectric constant and dielectric loss with frequency in the range of 20-3MHz was carried out at room temperature. The low-temperature dc conductivity behaviour follows Motts law, confirming the variable range hopping mechanism in all the composites. All the composites showed P-E and M-H hysteresis loops; which confirm the ferroelectric and ferrimagnetic nature of the composites. At temperatures below 173K, an increase in coercivity and saturation magnetization is observed due to frozen spins. The coupling between ferroelectric and ferromagnetic ordering was confirmed by room temperature magneto-dielectric studies. The decrease in real part of dielectric constant and dielectric loss was observed with an increase in the applied magnetic field. An appreciable increase in percentage magneto-capacitance was observed at lower frequencies and with the increase of ferrite content in the composites. The magneto-electric coupling coefficient was calculated by using the expansion of the thermodynamic potential phi (for x=0.15) and was found to be 3.397x10(-2) (emu/g)(-2).