Investigation of structural, optical, dielectric and magnetic properties of LaNiO3 and LaNi1-xMxO3 (M = Fe, Cr & Co; x=5%) nanoparticles

This paper reports the synthesis of pure and doped lanthanum nickel oxide (LaNiO3) nanoparticles (NPs) using auto-combustion route. Various characterization techniques were employed for the investigation of the effect of transition metal doping on the structural, optical, magnetic and frequency dependent dielectric properties of this system. X-ray diffraction (XRD) results were used to calculate the crystallite size and phase composition of the nanoparticles. The well intense peaks in the XRD pattern confirmed the perfect doping of transition metal ions (Fe, Cr, Co) in the LaNiO3 lattice structure. The scanning electron microscopy (SEM) confirmed the porous surface morphology of the nanoparticles. The presence of various functional groups, stretching and vibrational modes were analyzed by the Fourier Transform Infra-Red (FTIR) technique. The energy band gap (E-g) of the synthesized materials were calculated from the absorbance spectra using Tauc's relation. The band gap was observed to increase with doping indicating blue shift. The frequency dependent dielectric properties were measured at room temperature using LCR meter in the frequency range of 42 Hz to 5 MHz. It was observed that the dielectric constant and dielectric loss decreases with the increase in frequency. This decrease in dielectric constant as well as in dielectric loss with increase in frequency may be attributed to decreased polarization at higher frequency. The dielectric behaviour of LaNiO3 based perovskite oxides is explained on the basis of Koop's theory which is based on Maxwell-Wagner two layer model. Vibrating sample magnetometer (VSM) was used to study the magnetic properties at room temperature and the obtained results confirmed the ferromagnetic nature of all the compositions.