Rietveld refined structure, ferroelectric, magnetic and magnetoelectric response of Gd- substituted Ni-Cu-Zn ferrite and Ca, Zr co-doped BaTiO3 multiferroic composites

•Multiferroic xNCZGF+(1-x)BCZT composites were synthesized by standard solid-state reaction process.•Rietveld refinement has confirmed both components of the composites maintain their characteristics in XRD patterns.•Maximum ɛ′ and minimum tanδE values were found for x = 0.10 composite.•Values of µi′ and Ms were enhanced in composites with an increase in NCZGF content.•Maximum response of αME (~173 mVcm−1Oe−1) was found in 0.1NCZGF+0.9BCZT composite. The room temperature magnetoeletric coupling was investigated thoroughly in various xNi0.48Cu0.12Zn0.40Gd0.04Fe1.96O4 + (1-x)Ba0.985Ca0.015Zr0.10Ti0.90O3 multiferroic composites. Ferrite and ferroelectric 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 spinel-perovskite structure with Fd3¯m, and P4mm space group, respectively. 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. 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, respectively. 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 resistance. The hysteresis loops (M-H and P-E) ensured the typical ferromagnetic and ferroelectric nature for all composites at room-temperature. Magnetic studies show an improvement of initial permeability, relative quality factor and magnetization, whereas magnetic loss gradually reduces with the increment