Ferrite nanoparticles of Ni[Formula: see text]Mn[Formula: see text]Zn[Formula: see text]Fe[Formula: see text]CexO4 ferrite system were produced using sol–gel auto combustion technique. X-ray diffraction analysis confirms the single phase cubic spinel structure of the samples with space group Fd-3m. Replacement of Fe[Formula: see text] ions by Ce[Formula: see text] ions increases the lattice parameter 8.4105 Å to 8.4193. Average crystallite size obtained from Scherrer method varies from 21.73[Formula: see text]nm to 22.71[Formula: see text]nm with replacement of Fe[Formula: see text] ions by Ce[Formula: see text] ions. Williamson–Hall and strain-size plot analysis confirms the nanocrystalline nature of the samples and the micro-strain induced in the cubic crystals is of tensile type. Cation distribution suggests that Zn[Formula: see text] ions occupy tetrahedral — A-site while Ni[Formula: see text] ions occupy octahedral — B-site. Majority of the Mn[Formula: see text] ions prefer A-site and majority of the Ce[Formula: see text] ions replace Fe[Formula: see text] ions at octahedral — B-site. High resolution transmission images confirm the homogeneity and nanoparticle nature of the samples. Two main characteristics absorption bands corresponding to spine structure are observed in the Fourier transmission infra-red spectra within the wavenumber range of 350–600[Formula: see text]cm[Formula: see text]. Stiffness constant, Young’s modulus, rigidity modulus, bulk modulus and Debye temperature were estimated using FTIR data. Debye temperature obtained from the Waldron equation varies from 676[Formula: see text]K to 692[Formula: see text]K with the addition of Ce[Formula: see text] ions. Higher values of elastic moduli are suitable for industrial applications due to increased mechanical strength.

The stoichiometric compositions of a ferrite system with a chemical formula CoCr0.5DyxFe1.5−xO4 where x = 0.0, 0.025, 0.05, 0.075 and 0.1 were prepared by the sol-gel auto-combustion method. The structural, morphological and magnetic properties were studied by the X-ray diffraction (XRD), infra-red spectroscopy (IR), scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. XRD analysis confirmed the cubic spinel structure of the prepared samples without the presence of any impurity and secondary phases. Selected area electron diffraction and IR measurements gives further confirmation to the XRD observations. Considering that strain mechanism, elastic properties and cation distribution play a major role for controlling the magnetic properties and therefore these properties were precisely evaluated through reliable methodologies such as XRD and IR data. The cation distribution was determined by the X-ray diffraction data which are further supported by the magnetization studies. Magnetoelectric properties of CoCr0.5DyxFe1.5−xO4 + BaTiO3 have also been investigated. The mechanisms involved are discussed in the manuscript.

Polycrystalline Co-Zn nanoferrites doped with rare earth Dy3+ ions having general chemical formula Co0.9Zn0.2DyxFe1.9-xO4 (x = 0.0, 0.015, 0.03, 0.045 and 0.06) were synthesized via sol-gel auto-combustion route. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform Infrared Spectra (FTIR) were performed to investigate the structural, microstructral, surface morphology and elastic properties. Well indexed XRD patterns confirm the phase purity and cubic spinel structure of the samples. Fractional doping of Dy3+ ions shifts the Bragg’s lines slightly towards the lower angles which in turn increases the lattice lengths from 8.3795 Å to 8.3834 Å. The strain induced in the crystal lattice was estimated by using Williamson-Hall and Size – Strain Plot methods. Both methods confirm that the tensile type strain was induced in the crystal lattice and increases with the substitution of Dy3+ ions. Surface morphology of the samples was studied by using SEM images which reveals that the grains are almost spherical in nature and the size obtained is analogues with XRD results. FTIR spectra shows the existence of two main absorption bands within the wave number range 388 – 586 cm−1 which confirm the characteristics of spinel ferrites. Elastic properties were estimated by using FTIR data. Elastic moduli and Debye temperature increases with the substitution of Dy3+ ions which are interpreted on the basis of interatomic bondings.

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In the present work nanocrystalline NiFe2O4 samples were prepared by the sol-gel auto combustion technique. The synthesis was carried out by taking citric acid as fuel with metal nitrate to fuel ratio as 1:3. The obtained powder was annealed at 5500C for 4 h and then used for structural and magnetic investigations. Prepared nickel ferrite samples have been irradiated by gamma-ray (60Co) to examine the changes that occurred in structural properties. Structural properties of nickel ferrite nanoparticles before and after gamma irradiation were carried out by X-ray diffraction (XRD) technique. From the XRD pattern, it was observed that all the Braggs planes reveal cubic spinel structure before and after gamma irradiation. A close examination of the XRD pattern revealed the crystallite size of 21 nm and 19 nm for nickel ferrite samples before and after gamma irradiation respectively. The obtained results help in providing interesting and useful study for various applications of nickel ferrites.