Investigation of crystal structure, dielectric properties, impedance spectroscopy and magnetic properties of (1-x)BaTiO3 – (x)Ba0.9Ca0.1 Fe12O19 multiferroic composites

Abstract

Composites having composition (1-x)BaTiO3−(x)Ba0.9Ca0.1Fe12O19 (x = 0.10, 0.20, 0.30) were synthesized by conventional solid-state reaction technique. X-ray diffraction (XRD) was used to examine the phase formation. Rietveld refinement has been done using the FullProf suite which predicted the dual phase symmetry consisting hexagonal (P63/mmc) and tetragonal (P4mm) phases in the prepared composites. The dielectric properties of the obtained composites were investigated at different temperatures as a function of frequency in the range of 100 Hz to 7 MHz. The dielectric constant increases with an increase in Ca doped barium ferrite content. The composites showed usual dielectric dispersive behaviour with increasing frequency. The conduction mechanism and dielectric relaxation were examined by complex impedance spectroscopy (CIS). Nyquist plots of all composites showed two semicircles and their centers lied below the real axis. Magnetic characterization was performed by using a vibrating sample magnetometer (VSM) up to a field of 15 kOe at room temperature. The hysteresis loops reveal the ferromagnetic nature of the composites. The values of saturation magnetization, magnetic moment per formula unit, and corresponding coercivity increases with ferrite content and are maximum at x = 0.3. AC conductivity also increases with ferrite content. The variation of frequency exponent ‘n' of the power-law with temperature suggests that the overlapping large polaron tunneling (OLPT) model is appropriate to explain the mode of conduction in all samples.