Role of competing phases in the structural, magnetic and dielectric relaxation for (1−x)CoFe2O4+(x)BaTiO3 composites

Magnetoelectric composites of (1−x)CoFe2O4+(x)BaTiO3 (0.0≤x≤1.0) were prepared by ball milling method. X-ray diffraction analysis revealed the presence of cubic spinel (CoFe2O4) and tetragonal perovskite (BaTiO3) phases in the prepared composites. Scanning electron micrographs confirmed the homogeneous phase distribution in the obtained composites. The magnitude of saturation magnetization and linear magnetostriction decreased with increasing BaTiO3 content in the composite. Significant reduction in the magnetostrictive behavior is attributed to different elastic constants of the constituents which affect the mechanical coupling. In order to identify the different electro-active regions in the prepared composites, the experimental impedance spectroscopic data have been analyzed using different equivalent circuit models. The analysis of the impedance data is carried out by calculating the impedance of conductive (CoFe2O4) phase, resistive (BaTiO3) phase and interconnectivity between the two constituent phases. With increasing BaTiO3 content 'x' in the system, the dielectric permittivity decreased at low frequencies and increased at high frequencies. The observed behavior is mainly ascribed to the polarization in the CoFe2O4 and BaTiO3 phases at low and high frequencies, respectively. Moreover, the AC conductivity analysis suggested the mixed polaron hopping type of conduction mechanism in the prepared composites.