Synthesis of Ce-doped NiFe2O4 nanoparticles and their structural, optical, and magnetic properties

Abstract

The impact of Ce3+ doping on the crystallite size, microstructure, optical, and magnetic characteristics of nickel ferrite magnetic nanoparticles prepared by co-precipitation method is discussed in this article. The x-ray diffractometer, ultraviolet–visible spectrometer, photoluminescence spectrometer, electron paramagnetic resonance spectrometer, and vibrating sample magnetometer were used to characterize the prepared samples. The x-ray diffraction technique confirmed the cubic phase of all the samples and it further confirmed that the crystallite size steadily reduces from 55.8 to 33.5 nm as the Ce content rises from 0 to 0.15 then it rises to 41.8 nm with Ce content of 0.20. The lattice parameter ‘a’ was found to increase from 8.3442 to 8.3564 Å with the increase in Ce substitution. As the Ce content increases from 0 to 0.15, the optical band gap increased from 1.50 to 1.95 eV, thereafter, decreasing for Ce content x = 0.20. Fourier transform infrared spectroscopy reveals that the frequency corresponding to the Fe–O vibration of Ce-doped nickel ferrite nanoparticles is pushed towards a shorter wavenumber in contrast to pure nickel ferrite. The spinel structure of the synthesized samples confirmed by the x-ray diffraction pattern was also endorsed by the fourier transform infrared spectra. Photoluminescence spectra confirmed the visible emission from the undoped and Ce-doped nickel ferrite nanoparticles. Transmission electron microscopy analysis confirmed the rectangular shape of the nanoparticles and the reduction in average particle size from 58 to 37.5 nm with an increase in Ce concentration. Energy dispersive x-ray spectroscopy analysis confirmed the presence of Ni, Fe, Ce, and O elements. The explicit magnetic parameters like saturation magnetization, remanence, coercivity, squareness ratio, and magnetic moment were determined from magnetization versus applied field measurements. The result of BET analysis confirmed the porous nature of the Ce-doped NiFe2O4 which may be useful in photocatalytic activity. According to magnetic hysteresis curves, the saturation magnetization of nickel ferrite decreases from 51.9 to 22.6 emu/g after Ce content is 0.15. Vibrating sample magnetometer analysis also confirmed the superparamagnetism in nickel ferrite and cerium-doped nickel ferrite samples. Electron paramagnetic resonance confirmed the decrease in spin numbers and the spin relaxation time, after doping with cerium ions.