Tuning of magnetoelectric coupling in (1−y)Bi0.8Dy0.2FeO3–yNi0.5Zn0.5Fe2O4 multiferroic composites

Abstract

Magnetoelectric composites (1−y)Bi0.8Dy0.2FeO3 (BDFO)–yNi0.5Zn0.5Fe2O4 (NZFO) with y=0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 are synthesized by conventional solid state reaction route. The X-ray diffraction analysis confirms the coexistence of orthorhombic perovskite BDFO and spinel NZFO phases with no third phase. Microstructural and surface morphology are studied by Field Emission Scanning Electron Microscopy. Quantitative elemental analysis of the samples is carried out by Energy Dispersive X-ray Spectroscopy. The real part of the initial permeability increases and relative quality peak broadens with the ferrite content in the composites. Dielectric constant, loss tangent, relative quality factor and ac conductivity are measured as a function of frequency at room temperature. The dielectric constant shows usual dielectric dispersion at lower frequencies due to Maxwell–Wagner type interfacial polarization. The complex impedance spectroscopy is used to distinguish between the grain and grain boundary contribution to the total resistance. The modulus study reveals the ease of polaron hopping and negligibly small contribution of electrode effect. The magnetic hysteresis has been studied to know the response of NZFO phase to the applied magnetic field in the composite. The saturation and remanent magnetization are found to increase with increase in NZFO in the composite. The magnetoelectric voltage coefficient, αME is measured as a function of applied dc magnetic field. The tuning of ferrite percentage and dc magnetic field results in highest αME (~66mV/cmOe) for the composite with 40% NZFO at 4.7kOe which is attributed to the enhanced mechanical coupling between the two phases. The incorporation of BDFO and NZFO enhances the multiferroic properties in the present composite which are quite promising from application point of view.