A. Lakshman

Bio: A. Lakshman is an academic researcher from Papua New Guinea University of Technology. The author has contributed to research in topics: Dielectric & Electrical resistivity and conductivity. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

HIGH-FREQUENCY DIELECTRIC BEHAVIOR OF INDIUM AND CHROMIUM SUBSTITUTED Mg Mn FERRITES

Abstract: Dielectric properties such as DC resistivity (ρ), dielectric constant (e) and dielectric loss factor (tan δ) have been measured for Mg0.9Mn0.1InxFe2-xO4 and Mg0.9Mn0.1CryFe2-yO4 at room temperature. The composition dependence of ρ, e and tan δ and the frequency dependence of e and tan δ are presented in this paper. The resistivity increases while the dielectric constant decreases with increasing concentrations of indium and chromium ions. The dielectric loss factor at 100 kHz increases with composition for the samples 0.1 ≤ x ≤ 0.9 and 0.1 ≤ y ≤ 0.7. The dielectric constant for a given sample decreases with increasing frequency showing the normal dielectric behavior. The values of dielectric loss factor have been found to increase with frequency for the samples corresponding to x or y = 0.1 to 0.5; while other samples showed abnormal dielectric behavior. The observed variations in ρ are explained by Verwey's hopping mechanism while the variations in e and tan δ with composition and frequency are explained by space charge polarization using Koop's theory. Higher values of DC resistivity and low dielectric losses suggest that the prepared materials have great potential for microwave and high-frequency applications.

Cation distribution: a key to ascertain the magnetic interactions in a cobalt substituted Mg–Mn nanoferrite matrix

Abstract: The effect of Co2+ substitution into nanocrystalline Mg-Mn ferrite synthesized by a solution combustion technique has been studied. The cation distribution has been inferred from X-ray diffraction, the magnetization technique, and Mossbauer spectroscopy. The X-ray analysis and cation distribution data have been used to investigate the detailed structural parameters such as hopping lengths, ionic radii of tetrahedral and octahedral sites, oxygen positional parameter, site bond as well as edge lengths, bond lengths, and bond angles. The variation in the theoretically predicted bond angles suggested the strengthening of the A-B super-exchange interactions, and the same has been supported by M-H and M-T, as well as by Mossbauer studies. The ZFC-FC study revealed that anisotropy increases with the incorporation of cobalt ions. The values of magneton number, theoretical lattice parameter, and Curie temperature that have been calculated by using the cation distribution are found to match well with the experimentally obtained values.

Comparative study of structural, mechanical and electrical properties of Ni 0.8 Co 0.1 Cu 0.05 Mn 0.05 Fe 2 O 4 prepared from different combustion routes

Abstract: Comparative studies on the structural, mechanical and electric properties of Ni0.8Co0.1Cu0.05Mn0.05Fe2O4 prepared by solid state combustion and solution combustion routes were studied. The X-ray diffraction patterns reveal the cubic spinel phase formation with an extra Fe2O3 phase for Ni0.8Co0.1Cu0.05Mn0.05Fe2O4 prepared by the solid state combustion method in contrast to the single cubic spinel phase formation for ferrites obtained from other routes. Scanning electron microscopic images show loosely agglomerated grains with comparatively large grain size for Ni0.8Co0.1Cu0.05Mn0.05Fe2O4 prepared by solid state combustion, whereas there are well defined grains with distinct grain boundaries and smaller grain size for solution combustion route ferrite. Micro-strains calculated from XRD show a higher value for ferrite obtained from the solution combustion method route. The Young's modulus also show higher values for ferrite prepared from solution combustion, asserting comparatively high spontaneous magnetostriction in the magnetic domains of these ferrite particles. The fourier transform infrared study reveals the octahedral and tetrahedral bond formation in the authors’ ferrites prepared by both methods. Despite comparatively higher values of electric resistivity for solid combustion route ferrite, the authors’ combustion route ferrite can serve as a competent phase for application in transducer or sensor devices.