C. Murugesan

Impact of Gd3+ substitution on the structural, magnetic and electrical properties of cobalt ferrite nanoparticles

In this work, we have focused on the influence of Gd3+ substitution on the structural, magnetic and electrical properties of cobalt ferrite synthesized using a sol–gel auto-combustion method. The powder X-ray diffraction analysis reveals that the Gd-substituted cobalt ferrites crystallize in a single phase spinel structure for lower concentrations of Gd3+, while a trace of GdFeO3 appears as a minor phase for higher concentrations. Raman and Fourier transform infrared spectra confirm the formation of the spinel structure. Furthermore, Raman analysis shows that the inversion degree of cobalt ferrite decreases with Gd3+ doping. The field emission scanning electron microscopy images show that the substitution of small amounts of Gd3+ causes a considerable reduction of the grain size. Studies on the magnetic properties reveal that the coercivity of Gd-substituted cobalt ferrites enhances from 1265 Oe to 1635 Oe, the saturation magnetization decreases monotonically from 80 emu g−1 to 53.8 emu g−1 and the magnetocrystalline anisotropy constant increases from 5.8 × 105 erg cm−3 to 2.23 × 106 erg cm−3 at 300 K. The electrical properties show that the Gd3+ doped samples exhibit high dielectric constant (616 at 100 Hz) and ac conductivity (4.83 × 10−5 S cm−1 at 100 Hz) values at room temperature. The activation energy is found to decrease from 0.408 to 0.347 eV with the rise in Gd3+ content. The impedance study brings out the effect of the bulk grain and the grain boundary on the electrical resistance and capacitance of cobalt ferrite. Gd substitution and the nano-size of cobalt ferrite enhance the electrical and magnetic properties which could enable a higher memory storage capability.

PHASE EVOLUTION IN BiFeO3 NANOPARTICLES PREPARED BY GLYCINE-ASSISTED COMBUSTION METHOD

We report here the evolution of phase purity in BiFeO3 (BFO) nanoparticles prepared by a novel glycine-assisted combustion method. The study of phase evolution with temperature, in nanoparticles of BFO is carried out using X-ray diffraction (XRD) and thermogravimetry (TG) coupled with differential scanning calorimetry (DSC). Optimum annealing conditions for the synthesis of single-phase BiFeO3 nanoparticles are obtained. The morphology and average grain size of the nanoparticles are determined using a scanning electron microscope (SEM) and an atomic force microscope (AFM), respectively. In situ microanalysis revealed that there are no significant deviations in the stoichiometry of the prepared compound. The magnetic behavior of BFO nanoparticles at 300 K has been studied using a vibrating sample magnetometer (VSM). A weak hysteresis loop observed is suggestive of the presence of partially destructed antiferromagnetic arrangement of moments in the material. Low temperature magnetization measurements reveal the presence of spin glass–like transition in the nanoparticles of BFO. A well-developed ferroelectric hysteresis loop has been observed at room temperature at a maximum applied field of 45 kV/cm. The nanoparticles of BFO in the present study are found to possess both magnetic and ferroelectric order at room temperature.

Structural and Magnetic properties of Barium Hexaferrrite Prepared through Sol-Gel Auto combustion technique

Barium Hexaferrite nano particles were prepared through glycine assisted sol-gel auto combustion method with a minimal GNR (glycine to nitrate ratio) and the pH values of 4, 6 and 9. The present work aimed at the study on the effect of pH on the synthesis, structural and magnetic properties of barium hexaferrite samples. X-Ray Diffraction patterns reveal the formation of hexagonal magneto-plumbite structure of BaFe12O19 with a weak intensity of secondary phase in the case of pH 4 and pH 6 samples. Interestingly disappearance of secondary phase at pH 9 sample was noticeable feature. SEM micrographs of the samples show the formation of characteristic hexagonal shape of Barium hexaferrite. Constituent elements and chemical composition were analyzed using EDX spectrum. FTIR spectra show the different metal-oxygen stretching vibration modes at 440, 546 and 596-640 cm−1 which confirms the formation of BaFe12O19. In addition pH 4 and pH 6 samples show a weak band at 770 cm−1 revealing the formation of secondary ...

Dielectric properties of Mn0.5Zn0.5Fe2O4 ferrite nanoparticles

Mn0.5Zn0.5Fe2O4 ferrite nanoparticles have been prepared by sol-gel auto-combustion method with a view to understand the role of oxidizer to fuel ratio (OFR) on the dielectric properties. XRD study shows the formation of cubic ferrite with spinel structure and particle size increases with the increase in concentration of fuel. Dielectric properties and AC conductivity of the sample measured at room temperature are reported. OFR plays a vital role in determining the dielectric properties and AC conductivity of the prepared samples.