Santosh S. Jadhav

Electrical and magnetic properties of Cr3+ substituted nanocrystalline nickel ferrite

The magnetic and electrical properties of Cr3+ substituted nickel ferrite synthesized by wet chemical route have been studied. Particle size measured from x-ray diffraction and from transmission electron microscopy images confirms the nanosize dimension of prepared particles. Magnetic parameters such as coercivity and saturation magnetization are measured from vibrating sample magnetometer. Magnetization, ac susceptibility, electrical resistivity, and Mossbauer measurements were carried out. Electrical properties such as ac resistivity as a function of frequency and dc resistivity as a function of temperature were studied for various Cr3+ substitutions in nickel ferrite. The dielectric properties such as dielectric constant (e′) and dielectric loss (e″) were also studied. The dielectric constant and dielectric loss obtained for the ferrites prepared through wet chemical route posses a value lower than that of the ceramically prepared samples of the same composition. The resistivity obtained is higher than...

Effect of Zn substitution on magnetic properties of nanocrystalline cobalt ferrite

The Zn substituted cobalt ferrite nanoparticles having the generic formula Co1−xZnxFe2O4 (x=0.0–0.7) were prepared by wet chemical coprecipitation technique using analytical reagent (AR) grade sulphates. The prepared samples were heated at 150 °C to remove water molecules and then annealed at 725 °C for 16 h. Investigation of the structural properties were carried out using x-ray diffraction, transmission electron microscopy (TEM), and scanning electron microscopy techniques. The nanocrystalline nature of the samples is confirmed by TEM data. Substitution of the nonmagnetic Zn2+ ions considerably changes the magnetic properties. Neel’s model fails to explain the observed magnetic behavior above x=0.2. For x≥0.2 the Yafet–Kittel model can be fitted. AC susceptibility measurements confirm the decrease in Curie temperature.

Rietveld structure refinement, cation distribution and magnetic properties of Al3+ substituted NiFe2O4 nanoparticles

Ferrite samples of Al3+ substituted NiFe2O4 nanoparticles were prepared by wet chemical co-precipitation method. The samples were obtained by annealing at relatively low temperature at 600 °C and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and ac susceptibility. On applying the full pattern fitting of Rietveld method using FullProf program, exact coordinates of atoms, unit cell dimensions, atom ion occupancy, degree of inversion as well as crystallite size and residual microstrain have been determined. The lattice parameter, density, particle size, lattice strain, magnetization, magneton number, and Curie temperature are seen to decrease with increasing A13+ content whereas the specific surface area, porosity, coercive force, shows an increasing trend with A13+ content. Cation distribution is obtained from XRD and Rietveld method and the variation of the cation distribution has been discussed on ...

Influence of Ce4+ ions on the structural and magnetic properties of NiFe2O4

The effect of Ce4+ substitution in NiFe2O4, with a chemical formula Ni1-2xCexFe2O4 (0 ≤ x ≤ 0.25), ferrite prepared by a solid-state reaction is presented in this paper. Ce4+ ions enter the NiFe2O4 lattice by replacing Ni2+ and swell the lattice. This enlarges the lattice constant, which results in a moderate distortion of the lattice. The r.m.s. strain increases from 0.411 × 10−3 to 0.471 × 10−3 with increasing Ce4+ content. SEM images revealed that Ce4+ promotes grain growth in NiFe2O4. It was also revealed that x-ray density and porosity decreases, whereas a significant increase in the bulk density is observed with the Ce4+ content. Substitution of Ce4+ for Ni2+ caused a decrease in the saturation magnetization from 41.3 to 25.12 emu/g and a decrease in the Curie temperature of the nickel ferrite from 830 to 594 K, whereas the coercivity increased from 59.48 to 458.25 Oe.

STRUCTURAL PROPERTIES AND CATION DISTRIBUTION OF Co{Zn NANOFERRITES

The soft spinel ferrite system having the general formula Co1-xZnxFe2O4 with x varying from 0.0 to 0.7 has been prepared by wet-chemical co-precipitation technique. The prepared samples were characterized by XRD technique. The analysis of XRD pattern revealed the formation of single-phase cubic spinel structure. The Bragg peaks in XRD pattern are broader indicating fine particle nature of the sample. XRD data have been used to study structural parameter and cationic distribution in Co–Zn ferrite. The particle size is of nanometer dimension. Cation distribution results suggest that Co2+ occupy B-site, Zn2+ occupy A-site, and Fe3+ occupy both the A- and B-site.

The structural and magnetic properties of dual phase cobalt ferrite

The bismuth (Bi3+)-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co2+ by trivalent Bi3+ cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi3+ doping levels have been identified from the digital photoimages recorded using scanning electron microscopy. The hyperfine interactions, like isomer shift, quadrupole splitting and magnetic hyperfine fields, and cation distribution are confirmed from the Mossbauer spectra. Saturation magnetization is increased with Bi3+-addition up to x = 0.15 and then is decreased when x = 0.2. The coercivity is increased from 1457 to 2277 G with increasing Bi3+-doping level. The saturation magnetization, coercivity and remanent ratio for x = 0.15 sample is found to be the highest, indicating the potential of Bi3+-doping in enhancing the magnetic properties of cobalt ferrite.

Crystal chemistry and single-phase synthesis of Gd3+ substituted Co–Zn ferrite nanoparticles for enhanced magnetic properties

Rare earth (RE) ions are known to improve the magnetic interactions in spinel ferrites if they are accommodated in the lattice, whereas the formation of a secondary phase leads to the degradation of the magnetic properties of materials. Therefore, it is necessary to solubilize the RE ions in a spinel lattice to get the most benefit. In this context, this work describes the synthesis of Co–Zn ferrite nanoparticles and the Gd3+ doping effect on the tuning of their magnetic properties. The modified sol–gel synthesis approach offered a facile way to synthesize ferrite nanoparticles using water as the solvent. X-ray diffraction with Rietveld refinement confirmed that both pure Co–Zn ferrite and Gd3+ substituted Co–Zn ferrite maintained single-phase cubic spinel structures. Energy dispersive spectroscopy was used to determine the elemental compositions of the nanoparticles. Field and temperature dependent magnetic characteristics were measured by employing a vibration sample magnetometer in field cooled (FC)/zero field cooled (ZFC) modes. Magnetic interactions were also determined by Mossbauer spectroscopy. The saturation magnetization and coercivity of Co–Zn ferrite were improved with the Gd3+ substitution due to the Gd3+ (4f7)–Fe3+ (3d5) interactions. The increase in magnetization and coercivity makes these Gd3+ substituted materials applicable for use in magnetic recording media and permanent magnets.

Structural and Frequency Dependence Dielectric Properties of Magnesium Doped Nickel Ferrite

The structural and dielectric properties of magnesium substituted nickel ferrite having the general formula of Ni1xMgxFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) has been studied as function of Mg ion concentration. The samples were prepared by sol-gel auto-combustion method. The powder X-ray diffraction patterns confirm single phase cubic structure. The variation of lattice constant ‘a’ increases with Mg content x, the average particle size of these ferrites as determined from Scherrer’s relation and TEM is in the range of few ten nanometer. The dielectric constant decreases with increase in frequency and Mg content x. The dispersion of dielectric constant was discussed in the light of Koop’s theory. KeywordsFerrite, Sol-gel method, XRD and dielectric properties.