E. M. Mohammed

Effect of Gd3+ doping on the structural and magnetic properties of nanocrystalline Ni–Cd mixed ferrite

A series of nickel–cadmium ferrite, Ni0.9Cd0.1GdxFe2−xO4 (x=0, 0.1, 0.2 and 0.3), was prepared through the sol–gel technique. Samples were characterized using x-ray diffraction (XRD), Fourier transform infrared spectroscopy, a wavelength dispersive x-ray fluorescence spectrometer, a transmission electron microscope and a vibrating sample magnetometer. XRD analysis confirmed the formation of single-phase spinel structure in all the samples. The effect of Gd3+ doping on the crystalline phase, crystallite size and magnetic properties was investigated in detail. Gadolinium doping improved the crystallinity and induced compressive strain in Ni–Cd mixed ferrite. The lattice parameter was observed to increase for minor Gd3+ doping (up to x=0.1); however, further doping resulted in a reduction of the lattice constant. The saturation magnetization decreased and coercivity increased with an increase in gadolinium content.

Effect of Samarium Substitution on the Structural and Magnetic Properties of Nanocrystalline Cobalt Ferrite

A series of samarium-substituted cobalt ferrites ( with , 0.05, 0.10, 0.15, 0.20, 0.25) was synthesized by the sol-gel method. The structural characterizations of all the prepared samples were done using XRD and FTIR. These studies confirmed the formation of single-phase spinel structure in all the compositions. The increase in the value of lattice parameter with increase in samarium concentration suggests the expansion of unit cell. The Hall-Williamson analysis is used for estimating the average crystallite size and lattice strain induced due to the substitution of samarium in the prepared samples. Crystallinity and the crystallite size are observed to increase with the concentration of samarium. The surface morphology and particle size of a typical sample were determined using SEM and TEM respectively. The substitution of samarium strongly influences the magnetic characteristics, and this is confirmed from the magnetization measurements at room temperature.

A comparative study of structural, electrical and magnetic properties of magnesium ferrite nanoparticles synthesised by sol-gel and co-precipitation techniques

Nano-sized magnesium ferrite was synthesised using co-precipitation and sol-gel techniques. Structural characterisation was performed using X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectrometer and scanning electron microscope. XRD analysis reveals the prepared samples are single phasic without any impurity. Particle size calculation shows that the crystallite size of sol-gel prepared samples is 9 nm and co-precipitation sample is 11 nm. FTIR analysis confirmed spinel structure of the prepared samples. Magnetic measurements show that both the samples are ferromagnetic with a high degree of isotropy in co-precipitation derived sample. The frequency dependence of the dielectric constant in the range 100 Hz–20 MHz was also investigated in the temperature range 303–533 K. The results of both the samples followed Maxwell–Wagner model based on interfacial polarisation in consonance with Koops theory.

Effect of Sintering Temperature on the Structural Magnetic and Electrical Properties of Zinc Ferrite Samples

Effect of Sintering Temperature on the Structural Magnetic and Electrical Properties of Zinc Ferrite Samples Zinc ferrite was synthesized by sol–gel method. Fine particles with different grain size were obtained by subsequent heat treatment at different temperatures. The structure of all the prepared samples was elucidated using XRD. Magnetic measurement shows a decrease in magnetization with increase in sintering temperature. The variation of AC conductivity and dielectric constant was studied as a function of frequency, temperature and grain size. The Maxwell-Wagner two layer model and electron hopping mechanism was used to explain the variation of conduction and polarization with frequency. The observed high permittivity and conductivity for small grains were explained on the basis of the correlated barrier hopping model.

Structural and electrical studies of Gd3+ substituted zinc ferrite nano particles

ABSTRACT Zinc ferrite nanoparticles with Gadolinium (Gd) ions substituted for iron in ZnGdxFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15) were prepared by sol – gel method. The X ray diffraction measurement confirmed the formation of single crystalline spinel structure in all the samples. The lattice constant increases with increase in Gd3+ ion concentration. The crystallite size calculated by Scherrer formula from the (311) peak varies from 19 nm to 8 nm. The particle morphology was studied by Transmission Electron Microscope (TEM). The XRF analysis confirmed the purity of the prepared samples. The variation of dielectric constant and loss factor with frequency showed normal behavior. The values of dielectric constant, dielectric loss factor and AC conductivity were found to increase with increase in Gd3+ ion concentration in zinc ferrite. AC conductivity measurements suggested conduction due to small polaron hopping. The composition and frequency dependence of dielectric parameter and AC conductivity is qualitatively explained.

Structural and magnetic properties of chromium doped zinc ferrite

Zinc chromium ferrites with chemical formula ZnCrxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125 nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM).

Electrical and magnetic properties of nano-sized magnesium ferrite

Nano-sized magnesium ferrite was synthesized using sol-gel techniques. Structural characterization was done using X-ray diffractometer and Fourier Transform Infrared Spectrometer. Vibration Sample Magnetometer was used to record the magnetic measurements. XRD analysis reveals the prepared sample is single phasic without any impurity. Particle size calculation shows the average crystallite size of the sample is 19nm. FTIR analysis confirmed spinel structure of the prepared samples. Magnetic measurement study shows that the sample is ferromagnetic with high degree of isotropy. Hysterisis loop was traced at temperatures 100K and 300K. DC electrical resistivity measurements show semiconducting nature of the sample.

Enhancement of electrical properties of manganese tungstate nanoparticles by beam irradiation

MnWO4 nanoparticles were synthesized using simple chemical precipitation method. The dielectric properties of irradiated and non-irradiated samples of monoclinic manganese tungstate nanoparticles have been studied as a function of frequency. It is found that electric properties such as dielectric constant, loss tangent and a.c. conductivity of the irradiated sample were much larger as compared to the non-irradiated sample, which has been attributed to defects and reduction in particle size caused by the beam irradiation. The present investigation observed that the electron beam irradiation is an efficient technique to modify the electrical properties of MnWO4 nanoparticles.

Structural and electrical properties of neodymium substituted cobalt ferrite nanoparticles

A series of polycrystalline spinel ferrites with composition CoFe2-xNdxO4(x=0.0, 0. 05, 0.1, 0.15, 0.2, 0.25) have been synthesized by sol gel method. The structural characterizations of the prepared samples were done using XRD and TEM. The crystallite size shows an increase with the increase in the concentration of neodymium. The activation energy has been calculated from the temperature dependent DC conductivity measurements. The dielectric properties were studied and analyzed as a function of frequency. All the samples exhibit normal dielectric behaviour which is attributed to Maxwell- Wagner interfacial polarization.

Dielectric Behavior and AC Conductivity of Mg2+ Doped Zinc Ferrite Nanoparticles Synthesized by Sol-Gel Technique

Magnesium doped zinc ferrite Zn1−xMgxFe2O4 (x = 0.00, 0.25, 0.50, 1.00) was prepared by sol-gel technique. X-ray diffraction analysis revealed single cubic spinel structure with crystallite size ranging from 18 nm to 8 nm. Elemental analysis using XRF confirmed the purity of the samples. The lattice parameter was found to decrease with magnesium content. The observed dielectric behaviour is explained on the basis of Maxwell-Wagner two layer models. Variation of AC conductivity suggests conduction due to small polaron hopping. Both AC conductivity and dielectric constant increases with increases in temperature.