S.M. Patange

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 ...

Enhanced magnetic properties of Dy3+ substituted Ni-Cu-Zn ferrite nanoparticles

Dy3+ substituted Ni-Cu-Zn (Ni0.4Cu0.4Zn0.2DyxFe2−xO4) ferrite nanoparticles were obtained at 600 °C by synthesizing sol-gel auto-combustion method, and they exhibit a particle size of 12–21 nm. X‐ray diffraction patterns confirm the presence of secondary phase of DyFeO3 and Fe2O3 for the Dy3+ substituted samples. Ni‐Cu‐Zn ferries doped with Dy3+ possess better grain structure and growth than that of pure Ni‐Cu‐Zn ferrite. The saturation magnetization increases remarkably up to 81 emu/g with increasing the Dy3+ ions. The increased saturation magnetization related to increased exchange interactions between Fe‐Fe ions and also with increased particle size. Blocking temperature was found to decrease with increasing Dy3+ substitution. An enhancement in initial permeability and Curie temperature was observed with Dy3+ substitution.

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.

Random site occupancy induced disordered Néel-type collinear spin alignment in heterovalent Zn2+–Ti4+ ion substituted CoFe2O4

CoFe2O4, cobalt ferrite (CFO) nano-particles with composition CoZnxTixFe2−2xO4 (0 ≤ x ≤ 0.4) were synthesized by sol–gel autocombustion method. The effect of Zn2+–Ti4+ substitution on the structural, magnetic and frequency dependent permeability properties of the CFO nano-particles were investigated by X-ray diffraction, 57Fe Mossbauer spectroscopy, vibrating sample magnetometry, transmission electron microscopy and permeability analysis. The Rietveld refinement of XRD patterns confirm the single spinel phase and the crystallite size is found in the range of 22–32 nm. Cation distribution was estimated by refining the XRD pattern by Rietveld method, and shows Zn2+ ions at the tetrahedral A-sites, and Co2+ and Ti4+ ions at octahedral B-sites. The saturation magnetization (Ms) increased from 58 to 75 emu g−1 for up to x = 0.2 and then decreased, while the coercivity decreased continuously with Zn2+–Ti4+ substitution. Two distinct composition ranges with Zn2+–Ti4+ substitution are identified for which Ms variation with x is explained by the Neel and Yafet–Kittel models. The room temperature Mossbauer spectra are analyzed in detail for probing the magnetic properties of Fe based Zn2+–Ti4+ substituted CFO. The effect of Zn2+–Ti4+ substitution on various Mossbauer parameters, viz. hyperfine field distribution, isomer shift, quadrupole splitting, and line width, has also been studied. The variation of nuclear magnetic fields at the A and B sites is explained on the basis of A–B and B–B supertransferred hyperfine interactions. The CFO nanoparticle is considered to possess a fully inverse spinel structure with a Neel-type collinear spin alignment, whereas the Zn2+–Ti4+ substitution in CFO is found to be structurally and magnetically disordered due to the nearly random distribution of cations and the canted spin arrangement. This study also demonstrates that one can tailor the magnetic properties of CFO particles by optimizing the Zn2+–Ti4+ substitution. The increase in the permeability, saturation magnetization and lower loss factor makes the synthesized materials suitable for applications in microwave devices and deflection yokes.

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.

Spin glass behavior and enhanced but frustrated magnetization in Ho3+ substituted Co–Zn ferrite interacting nanoparticles

Nanoparticles of Ho3+ substituted in Co–Zn ferrites were synthesised by sol–gel method. The phase formation of these samples has been confirmed by X-ray powder diffraction technique. XRD Rietveld refinement carried out using the FULLPROF program shows that the Co–Zn ferrite retains its single phase cubic structure with space group Fd3m for x ≤ 0.05. Occupancy of the cations is explained on the basis of site preference, size and valance of the substitution cations. The nanostructure and morphology of prepared samples were investigated by field emission scanning electron microscopy and transmission electron microscopy. The elemental percentage of the constituent ions was determined using energy dispersive spectroscopy. The magnetic interactions among the nanoparticles were analyzed by employing a temperature dependent vibration sample magnetometer, field cooled (FC)/zero field cooled (ZFC) measurements. The ZFC and FC curves diverge below the blocking temperature exhibiting a ZFC cusp at 195–225 K. The saturation magnetization of Co–Zn ferrite increased linearly with Ho3+ substitution for x ≤ 0.05 and almost remains constant thereafter. The frequency dependence of the AC susceptibility measurements was performed on the sample. It shows a peak at around spin freezing temperature, with the peak position shifting as a function of driving frequency, indicating a spin-glass-like transition of the sample.

Rietveld Structure Refinement and Cation Distribution of Cr

Ferrite nanoparticles of Ni0.7Zn0.3Cr𝑥Fe2−𝑥O4 were prepared by a sol-gel autocombustion method. The prepared samples were shown to have a cubic spinel structure by applying the full pattern fitting of the Rietveld method. The unit cell dimension, discrepancy factor, and interatomic distance have been determined. As the Cr3