Study of the magnetoelectric coupling behavior of divalent cations substituted barium-zircon-titanate and gadolinium substituted nickel-copper-zinc ferrite multiferroic composites

Abstract

The room temperature magnetoeletric coupling was investigated thoroughly in various multiferroic (1-x)Ba0.985D0.015Zr0.10Ti0.90O3+xNi0.48Cu0.12Zn0.40Gd0.04Fe1.96O4 [(1-x)BDZT+xNCZGF] (where D = Ca, Sr) composites. Ferroelectric and ferrite phase of the composites have been prepared by the standard solid state reaction technique. Structural study was conducted by the X-ray diffraction (XRD) and the Rietveld refinement was adopted for further analysis of the structure. The refined XRD patterns confirmed all composites having a biphasic perovskite-spinel structure with P4mm and Fd 3m space group. Microstructural characteristics of all samples have been analyzed using Field Emission Scanning Electron Microscopy images. The magnetoeletricaly coupled composites is illustrated by an obvious modification in lattice, dielectric, ferroelectric and magnetic properties as a function of ferrite content. Frequency dependence of the dielectric constant exhibits dispersion, which can be modeled using a modified Debye function that considers the probability of several ions contributing to the relaxation. The dielectric constant of the composites was found to decrease with the addition of ferrite content in line with the theoretical estimations of the Bruggeman, Maxwell-Garnett, Lichtencker and Looyenga models. The dielectric constant and initial permeability were calculated theoretically using the different models and compared with the experimental values. The discrepancy between the calculated and experimental values of dielectric constant and initial permeability might be attributed to the diffusion of ions and interaction between two phases of the composites. The ac conductivity analysis revealed that the conduction mechanism is attributed to the small polaron hopping and also obeyed the Jonscher‟s power law. Complex impedance was evaluated using the Nyquist plot which ensured the dominance of both grain and grain boundary resistances. Magnetic studies show an enhancement of initial permeability, relative quality factor and saturation magnetization, whereas magnetic loss gradually reduces with the increment of ferrite content. The P-E hysteresis loops ensure the typical ferroelectric nature at room temperature for x  0.20. The simultaneous P-E and M-H hysteresis loops confirm the magnetoelectric coupling between ferroelectric and ferrite phases. Furthermore, the maximum magnetoelectric response ~173 mV/(cm Oe) and ~194 mV/(cm Oe) were found for 0.9BCZT+0.1NCZGF and 0.9BSZT+0.1NCZGF composite that could be utilized in the future multifunctional devices.