Crystal structure, dielectric, magnetic and improved magnetoelectric properties of xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 composites

Abstract

Magnetoelectric (ME) composites of NiFe2O4 (NFO) and Na0.5Bi0.5TiO3 (NBT) with composition xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 (x = 0.20, 0.40, 0.60) were prepared successfully by solid state reaction method. The crystal structure analysis was carried by using x-ray diffractometer, field emission scanning electron microscope—energy dispersive analysis of x-rays (FESEM-EDX) and Fourier transform infrared spectroscopy (FTIR). The presence of two individual phases corresponding to ferrite and ferroelectric was confirmed by XRD analysis of composites. Rietveld refinement of XRD data further confirms the existence of both cubic (Fd3m) and rhombohedral (R3c) symmetries. FESEM micrographs and EDX spectra revealed the reduction in grain sizes with increase in ferrite content. FTIR spectra depict two prominent absorption bands around 413 cm−1 and 618 cm−1. Dielectric response of these samples was recorded at frequency range 100 Hz–7 MHz for different temperature. Dielectric constant (ε′) and dielectric loss (tanδ) values found higher at low frequencies, decrease with increase in frequencies and become independent at higher frequencies. ε′ and tanδ both enhance with rising temperature and become more stable at higher frequencies. Complex impedance spectroscopy (CIS) investigation was used to understand dielectric relaxation and conduction mechanism in composites. Cole-Cole plots for all samples depict two semicircles and the centre of semicircles is depressed below real axis with temperature. Activation energy rises with increase in ferrite content in composites. Magnetic evaluation of the samples discloses the soft magnetic nature of these composites. The maximum value of saturation magnetization (MS = 22.82 emu g−1) and magnetic moment per formula unit (η = 0.92 μB) is observed for composition having higher NFO content. The highest ME response, α ∼ 1122 μV/cmOe is observed for the composite 0.60NiFe2O4-0.40Na0.5Bi0.5TiO3.