K. M. 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.

X-ray and infrared studies of chromium substituted magnesium ferrite

Abstract The ferrites of the composition MgCr x Fe 2− x O 4 with x =0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 were prepared by using the usual double sintering technique and characterized by X-ray diffraction and Infrared studies in the range of 200 to 800 cm −1 . The lattice parameters are calculated and are found to decrease with Cr substitution. The X-ray density decreases as Cr content increases. The distance between magnetic ions in both octahedral and tetrahedral sites decreases with increase in Cr. The cation distribution in this spinel system is determined from X-ray intensity calculations. The far infrared spectra obtained at room temperature in the range 200 to 800 cm −1 showed two absorption bands. The high frequency band ( ν 1 ) and low frequency band ( ν 2 ) are assigned to the tetrahedral and octahedral complexes, respectively. The force constants have been obtained from the infrared absorption data and their dependence with the internuclear distance has been discussed.

Effect of Cation Proportion on the Structural and Magnetic Properties of Ni-Zn Ferrites Nano-Size Particles Prepared By Co-Precipitation Technique

Ferrites having general formula Ni 1x Zn x Fe2O4 with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 were prepared by wet chemical co-precipitation method. The structural and magnetic properties were studied by means of X-ray diffraction, magnetization, and AC susceptibility measurements. The X-ray analysis confirmed the single-phase formation of the samples. The lattice parameter obtained from XRD data was found to increase with Zn content x. The cation distribution was studied by X-ray intensity ratio calculations. Magnetization results exhibit collinear ferrimagnetic structure for x 0.4, and which changes to non-collinear for x>0.4. Curie temperature T C obtained from AC susceptibility data decreases with increasing x.

Structural and magnetic properties of aluminium and chromium co-substituted cobalt ferrite

Polycrystalline cobalt aluminium chromium ferrites (CoAlxCrxFe2−2xO4) with varying Al–Cr substitution (0<x<0.5) have been prepared in pellet form by standard double sintering technique and studied by X-ray diffraction (XRD), magnetization and ac susceptibility measurements. The lattice constants are determined and the applicability of Vegards law has been verified. The saturation magnetization (σs) decreases with Al–Cr content (x), indicating reduction in ferrimagnetic behaviour. The variation of the saturation magnetic moment per formula unit measured at 300 K with Al–Cr content is satisfactorily explained on the basis of Neels colinear spin ordering model for x=0.0–0.3. Thermal variation of low field ac susceptibility measurements from room temperature to 860 K exhibits almost normal ferrimagnetic behaviour and the Neel temperature (TN) decreases with increasing Al–Cr content x, which is consistent with the observed decrease in σs with x.

Structural and magnetic properties of Co1+ySnyFe2-2y-xCrxO4 ferrite system

The samples of the series Co1+ySnyFe2- 2y- xCrxO4 ferrites with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and y = 0.05, were prepared by the usual double sintering ceramic technique. The single- phase spinel structure of the samples was confirmed by using X- ray diffractometry technique. The lattice parameter ’a’ with an accuracy of ± 0.002 Å were determined using Bragg peaks of XRD pattern. The lattice parameter ’a’ decreases with concentration, x, which is due to the difference in the ionic radii of Cr3+ and Fe3+ ions. The X- ray intensity calculations were carried out in order to determine the possible cation distribution amongst tetrahedral (A) and octahedral [B] sites. The X- ray intensity calculations show Cr3+ ions occupying B site. The saturation magnetization, σs, and magneton number, nB (the saturation magnetization per formula unit), measured at 300 K determined from high field hysteresis loop technique decrease with increase in concentration, x, suggesting a decrease in ferrimagnetic behaviour. Thermal variation of low field a.c. susceptibility measurements from room temperature to about 800 K exhibits almost normal ferrimagnetic behaviour and the Curie temperature, TC determined from a.c. susceptibility data decreases with increase in x.

X-ray diffraction and dielectric study of Co1−xCdxFe2−xCrxO4 ferrite system

Abstract The samples of the Cd–Cr co-substituted cobalt ferrite (Co 1− x Cd x Fe 2− x Cr x O 4 ) with x =0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by the usual double sintering ceramic technique and were characterized by means of X-ray diffraction (XRD) and dielectric measurements. X-ray analysis shows that the samples are cubic spinels (single phase). The lattice parameter a is determined from XRD data with an accuracy of ±0.002 A for x =0.0 to 0.5 and their variation with Cd and Cr addition is studied. The lattice parameter a increases with the compositional parameter x . the dielectric constant ( e ″), dielectric loss (tan δ ) and dielectric loss tangent (tan δ ) of Co 1− x Cd x Fe 2− x Cr x O 4 were measured at room temperature as a function of frequency. The measurements were carried out with the help of HP 4192 LF impedance analyzer in the range 100 Hz–1 MHz. It is observed that e ′, e ″ decrease with increasing frequency. The dielectric loss ( e ″) decreases with increasing frequency at a faster rate that the dielectric constant ( e ′). The parameter (tan δ ) decreases with increasing frequency.

Magnetic and electrical properties of aluminium and chromium co-substituted yttrium iron garnets

Abstract Polycrystalline yttrium aluminium-chromium iron garnets (Y 3 Al x Cr x Fe 5 − 2 x O 12 ) with varying Al-Cr substitution (0 ≤ x ≤ 1.0) have been prepared in the pellet form, and studied by X-ray diffraction, magnetization, a.c. susceptibility and electrical resistivity measurements. The lattice constants are determined and the applicability of Vegards law has been tested. The saturation magnetization (4π M s ) decreases linearly with increasing x from x = 0.1 to 1.0 indicating reduction in ferrimagnetic behaviour. Variation of saturation magnetic moment per formula unit at 300 K with x can be explained satisfactorily assuming the collinear spin ordering model. The Curie temperature ( T C ) decreases with increasing x which is consistent with the observed decrease in 4π M s with x . The activation energy ( E ) initially increases up to x = 0.6 and thereafter it levels off for further increase in x > 0.6.