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The rare earth element Pr3+ substituted nickel ferrite magnetic nanomaterials NiPrxFe2−xO4 (x = 0, 0.01, 0.02 and 0.03) have been synthesized by a sol–gel method at an annealing temperature of 550°C.The effect of Praseodymium ion on structural, optical, magnetic and ferroelectric properties are being investigated. The structural analysis showed that the prepared material exhibited a cubic spinel structure having Fd3m space group. The crystallite size was evaluated by W–H plot and ranged from 14 to 29 nm. The lattice constants also displayed a decrease for the samples containing the higher concentrations of Pr3+ (x = 0.02 and 0.03). The SEM analysis revealed agglomeration in the prepared ferrites. The average particle size of 28 nm for NiFe2O4 material has been observed by HRTEM. The bond length and force constant were also calculated, where the bond length increased, whereas the force constant decreased systematically with the increase in Pr3+ ion. The indirect band gap decreased from 2.28 to 1.85 eV with the increase of rare earth ion Pr, which indicated an improvement in the energy gap. The luminescence measurement demonstrated five emissions in visible range at 457, 483, 493, 508 and 520 nm, where there is a significant increase in intensity without any shift in emission wavelengths. The saturation magnetization decreased from 36.31 to 32.97 emu/g with the increase in Pr-ion. Similarly, the coercivity decreased from 175 to 48.69 Oe, which may be useful for low-core loss material. Thus, the improved optoelectronic, magnetic and ferroelectric properties of Pr3+ substituted nickel ferrite open a new window for technological grade material, which may be advantageous in various industries related to transformer core loss, photovoltaic cell, etc. [ABSTRACT FROM AUTHOR]

Co1-xPbxFe2O4 (x = 00-0.15) have been synthesized using citric acid modified sol-gel method. Samples for x ≤ 0.02 have been ball milled to reduce the particle size. Hence, all the materials under the study are in almost equal crystallite size (-15 nm). The phase purity and structural study have been carried out using X-ray powder diffraction (XRD) technique. The Rietveld refinement of XRD patterns reveals the increasing lattice parameter with the lead (Pb) concentration. Detailed analysis of the Raman spectroscopy data supports the XRD pattern analysis results. Magnetic hysteresis loop measurements have been performed using Vibrating Sample Magnetometer (VSM) at room temperature over field range of ±20 kOe. Magnetocrystalline anisotropy constant was calculated using Law of Approach (LA) to saturation, which shows increasing behavior till 2% Pb concentration. The large difference in experimental and theoretical saturation magnetic moment per formula unit shows existence of three sublattice model suggested by Yafet-Kittel. [ABSTRACT FROM AUTHOR]