Synthesis and characterization of Ni0.8Co0.2Fe2O4–Ba0.95Sr0.05TiO3 multiferroic composites

In this paper, structural, microstructural, dielectric, magnetic, ferroelectric, and magnetoelectric properties of a multiferroic composite with compositional formula (x) Ni0.8Co0.2Fe2O4+(1−x) Ba0.95Sr0.05TiO3 (where x=0.0, 0.02, 0.04, 0.06, 0.08, 0.10, 1.00) has been studied. Nanoparticles of Ni0.8Co0.2Fe2O4 ferrite have been prepared by the sol–gel method. Ba0.95Sr0.05TiO3 ceramic, synthesized by solid state reaction, has particle size in the micrometer range. X-ray analysis along with Rietveld refinement confirmed the formation of cubic spinel and perovskite structure for ferrite and ferroelectric phases, respectively. Transmission Electron Microscopy (TEM) analysis showed that Ni0.8Co0.2Fe2O4 particles have particle size in 25–60 nm range. Samples were characterized for the microstructural analysis by Scanning Electron Microscopy (SEM). Quantitative elemental analysis of the composite samples was carried out by Energy Dispersive X-ray Spectroscopy (EDS). Dielectric properties were studied as a function of frequency in the range 20 Hz–1 MHz for pure and composite samples. AC conductivity measurements suggested that small polaron hopping is the dominant conduction mechanism in the composites. Polarization vs. Electric field (P–E) and Magnetization vs. Magnetic field (M–H) hysteresis loop measurements respectively, confirmed good ferroelectric and ferromagnetic behavior of the composites. Complex impedance spectroscopy measurements at different temperatures confirmed the semiconducting nature of the composites. Magnetoelectric coupling between ferrite and ferroelectric phases was confirmed by measuring M–H hysteresis loops of electrically poled and unpoled samples.