Role of grain interface on dielectric and multiferroic properties of 0-3 type (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposites

Abstract

The (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 (0-3 type particulate) nanocomposites with x = 0.00, 0.02, 0.04, 0.06, 0.08, and 1.00 were prepared by the solid-state method. Cobalt ferrite crystallized into cubic crystal symmetry with an Fd3̄m space group. Strontium-substituted barium titanate crystallized into a tetragonal crystal structure with a P4mm space group. Field emission scanning electron microscopy and transmission electron microscopy techniques show the distribution of different sizes of particle. Polarization vs electric field curves show the highest maximum polarization (Pm) of 10.26 μC/cm2, remnant magnetization (Pr) of 11.70 μC/cm2, and coercivity (Ec) of 19.95 kV/cm for x = 0.04 composition at 35 kV/cm. However, it is smaller than the Ba0.8Sr0.2TiO3 phase (Pm = 16.86 μC/cm2, Pr = 13.20 μC/cm2, and EC = 10.80 kV/cm). The highest dielectric constant of around 9800 was found for x = 0.04 composition, with a very small dielectric loss factor of about 0.02, i.e., less than even 2%. This is ∼10 times compared to that of Ba0.8Sr0.2TiO3 (BSTO), which has been explained by considering interaction at the interface of CoFe2O4 (CFO) and BSTO, leakage current, and variation of the lattice parameter of BSTO in (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposite. The magnetic hysteresis loops show squeezing near the origin. The magnetic parameters like coercivity, remnant magnetization, and saturation magnetization increased with the increase in the CoFe2O4 weight fraction. Magnetic interaction between surfaces of magnetic CFO and non-magnetic BSTO is evident from the ΔH vs M plots, and it also evidences the magnetism at the surface of BSTO due to uncompensated spins.