Multiferroic properties of magnetoelectrically coupled lithium-copper-nickel-zinc ferrite and rare earth substituted barium-dysprosium-titanate composites

Abstract

Multiferroic xLi0.1Ni0.3Cu0.1Zn0.4Fe2.1O4+(1-x)Ba0.95R0.05Ti0.95Dy0.05O3 composites (where, R = Sm and Gd; x = 0.00, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, and 1.00) were prepared by the conventional solid-state reaction technique. The structural, real part of initial permeability, M-H hysteresis loop, dielectric properties, ac conductivity, impedance spectroscopy, ferroelectric property, and magnetoelectric voltage coefficient of the composites have been studied in detail. The phase identification of ferrite and perovskite structure was executed by the Rietveld refinement analysis of the XRD patterns. The ferrite phase of Li0.1Ni0.3Cu0.1Zn0.4Fe2.1O4 forms a cubic spinel structure. On the other hand, ferroelectric phases of Ba0.95Sm0.05Ti0.95Dy0.05O3 and Ba0.95Gd0.05Ti0.95Dy0.05O3 show tetragonal perovskite structure. There is a slight change in the lattice parameters in the composites results from the stress between these phases. The density decreases and the average grain diameter increases with ferrite content in the composites. The real part of initial permeability and relative quality factor enhance with increasing ferrite phase because of high magnetic LNCZFO. Nevertheless, the composites with Sm show relatively higher real part of initial permeability compared to the composites with Gd. Saturation magnetization is found to increase with increasing ferrite content of the composites. The dispersive dielectric nature is observed in the low-frequency region due to Maxwell-Wagner type interfacial polarization. In lower frequency regions (20 Hz-104 Hz) some composites have a higher dielectric constant than the constituent phases due to large interfacial polarization created from the heterogeneous interface of the constituents. The shifting of the ferroelectric transition temperature in the composites confirmed the interaction between the constituent phases. The ac conductivity of the studied composites result from small polaron hopping mechanism and satisfied the Jonscher’s power law. Non-Debye type relaxation is found in the studied composites because each composite exhibits a depressed semicircle. The presence of Ni and heterogeneity have a significant effect on the ferroelectric properties of the composites. The maximum magnetoelectric voltage coefficient (αME) of 172 mV/cmOe is obtained for 0.10LNCZFO+0.90BGTDO composites. This value of αME may be a suitable alternative to Pb-based multiferroics for the application of modern multifunctional devices.