Mohd. Hashim

Structural, Dielectric, FT-IR and Complex Impedance Properties of Cobalt Ferrite Nanoparticles

Cobalt ferrite nanoparticles having the general formula CoFe2−xCuxO4 (0.0 ≤ x ≤ 0.5) were prepared by sol‐gel method and characterized by using X‐Ray diffraction (XRD), scanning electron microscopy (SEM ), Fourier transform infrared spectroscopy (FTIR), dielectric and impedance spectroscopy measurements. Confirmation of the single phase cubic spinel structure was made by using X‐ray diffractometer. Lattice parameter ‘a’ is found to decrease with increasing the doping contents. Debye‐ Scherer formula was used for finding the particle size and found in the range 30–45 nm. Morphological analysis was made by scanning electron microscopy which shows agglomerated flakes of particles having large pores on the surface. FT‐IR spectra show two absorption bands assigned to the tetrahedral and octahedral complexes in the frequency range 400–600 cm−1. The variation of dielectric properties e′, e, tanδ with frequency reveals that the dispersion is due to Maxwell‐Wagner type of interfacial polarization. Impedance spectr...

Structural, Dielectric and Magnetic Properties of Nano-Crystalline Ni-Mg Ferrites Prepared by Citrate-Gel Auto Combustion Method

Nano-particles of Ni0.5Mg0.5Fe2-xCrxO4 \( \left( {0 \le {\text{x}} \le 1.0} \right) \) have been synthesized by citrate-gel auto combustion method. X-ray diffraction (XRD) and infrared spectroscopy (IR) were used to study the structural changes taking place with varying Cr concentration. Morphological analysis was made by scanning electron microscopy. The dielectric and magnetic properties were investigated by ac impedance spectroscopy and vibrating sample magnetometer (VSM), respectively. X-ray diffraction analysis assured the formation of single phase cubic spinel structure. Infrared spectroscopic studies revealed two main absorption bands in the range 400–800 cm−1 arising due to tetrahedral (A) and octahedral (B) site vibrations. The dielectric properties have been carried out as a function of frequency (42 Hz–5 MHz) at room temperature. The dielectric behavior is explained on the basis of interface polarization, arising from the heterogeneous nature of ferrites structure. In general, substitution of chromium ion plays an important role tailoring the structural, dielectric and magnetic properties of the ferrite material.

Structural and magnetic properties of Fe doped CeO2 thin films

Pure and Ce0.95Fe0.05O2 thin films have been fabricated on LaAlO3 (100) substrate using pulsed laser deposition techniques at 200mTorr oxygen partial pressure and then characterized by various techniques viz. X-ray diffraction, atomic force microscopy, NEXAFS, and dc- magnetization measurements to explore the structural and magnetic properties of pure and Fe doped CeO2 thin films. The XRD patterns indicate that pure and Ce0.95Fe0.05O2 films have single phase polycrystalline behavior. The surface roughness measured using AFM microscopy found to decrease with Fe doping and revealed that both the films are nanocrystalline. The electronic structure measured at Fe L3,2 edge infer that Fe-ions in mixed valence states (Fe3+ and Fe2+) in Fe doped CeO2film. DC-magnetization measurements showed that pure and Fe doped CeO2 films have ferromagnetic ordering at room temperature.Pure and Ce0.95Fe0.05O2 thin films have been fabricated on LaAlO3 (100) substrate using pulsed laser deposition techniques at 200mTorr oxygen partial pressure and then characterized by various techniques viz. X-ray diffraction, atomic force microscopy, NEXAFS, and dc- magnetization measurements to explore the structural and magnetic properties of pure and Fe doped CeO2 thin films. The XRD patterns indicate that pure and Ce0.95Fe0.05O2 films have single phase polycrystalline behavior. The surface roughness measured using AFM microscopy found to decrease with Fe doping and revealed that both the films are nanocrystalline. The electronic structure measured at Fe L3,2 edge infer that Fe-ions in mixed valence states (Fe3+ and Fe2+) in Fe doped CeO2film. DC-magnetization measurements showed that pure and Fe doped CeO2 films have ferromagnetic ordering at room temperature.

Near-edge X-ray absorption fine structure spectroscopy and structural properties of Ni-doped CeO2 nanoparticles

ABSTRACT Ni-doped CeO2 nanoparticles were prepared by using the co-precipitation method. The prepared nanoparticles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The XRD results infer that Ni-doped CeO2 nanoparticles have single phase nature similar to that of pure CeO2 nanoparticles. We have calculated lattice parameters using Powder-X software, particle size using Scherer’s formula and strain using the Williamson-Hall method for all the synthesized samples. We have observed a systematic decrease in the lattice parameters, particle size and strain with an increase in Ni doping in CeO2. The FE-SEM micrographs also confirm that Ni-doped CeO2 have nanocrystalline behavior and particles are spherical shaped. From the Raman spectra, it is observed that the intensity of classical CeO2 vibration modes first increases then decreases with Ni doping. The NEXAFS spectra measured at Ce M4,5 and Ni L3,2 edges clearly indicate that Ce ions are in the +4 valence state and Ni ions are in the +2 valence state.

Effect of Co2+ substitution in Mg0.5Zn0.5−xCoxFe2O4 ferrite nanoparticles: Study of structural, dielectric and magnetic properties

Polycrystalline samples of Mg0.5Zn0.5−xCoxFe2O4 (0 ≤ x ≤ 0.5) with x varying from 0.0-0.5 synthesized by sol-gel auto ignition method. The X-ray diffraction analysis with Retvield refinement reveals the formation of single phase cubic spinel structure. The frequency dependent of real part of dielectric constant has been measured at room temperature and at 100 °C by using an ac impedance analyzer. Except x = 0.5, an increase in the dielectric constant is observed with increase in Co2+ substitution. Magnetic response has been seen by vibrating sample magnetometer (VSM) at room temperature. The saturation magnetization (MS) and coercivity (HC) increase with increasing the Co2+ substitution. The cation distribution estimated by Mossbauer spectroscopy shows that Co2+ and Mg2+ ions have their preference towards octahedral B site, on the other hand Zn2+ ions preferentially occupy tetrahedral A site, whereas Fe3+ ions are randomly distributed over A- and B-site. The as obtained results indicated that the substitu...

Theoretical investigation of hyperfine field parameters through mossbauer gamma ray

When a Mossbauer gamma-ray emitting or absorbing nucleus is placed in a crystalline environment, the quadrupole moment of the nucleus interacts with the electric field gradient set up by the ligands around it. In the transition |7/2〉 →|5/2〉 twelve lines are obtained. Applying the multipole radiation field theory and density matrix formalism, the determinant of coherency matrix, intensity and degree of polarization have been calculated for each line.

Study of Hyperfine Field Parameters through Mossbauer Transition

The hyperfine interactions provide basis to study structure of solids through the Mossbauer resonance. When a Mossbauer gamma‐ray emitting or absorbing nucleus is placed in a crystalline environment, the quadrupole moment of the nucleus interacts with the electric field gradient set up by the ligands around it. As a consequence, m‐quantum states get mixed up, if asymmetry parameter is non zero. In the transition |5/2〉→|3/2〈 six lines are obtained. It is found that the Kramer’s degeneracy in energy states exists. Applying the multipole radiation field theory and density matrix formalism, the determinant of coherency matrix, intensity and degree of polarization have been calculated for each line. The coherency matrix, the intensity and the degree of polarization are found non zero.

Structural, Dielectric, Microstructural Properties of Ni0.7Zn0.3Fe2−xAlxO4 Ferrite Nanoparticles Through Citrate‐Gel Method

Study of structural and electrical properties of Al3+ doped Ni0.7Zn0.3Fe2−xAlxO4 (0.0≤x≤0.5) ferrite synthesized through citrate‐gel method has been carried out. The samples were characterized by using XRD and dielectric technique in the frequency range 42 Hz–5 MHz at room temperature. X‐ray diffraction studies confirmed that all the samples exhibit single phase cubic spinel structure. The variation in e′, and tanδ with frequency reveals that the dispersion is due to Maxwell‐Wagner type of interfacial polarization in accordance with Koop’s phenomenological theory.