Papers by Author: Muhammad Ali Malik

Abstract: Spinel ferrites, which have the general chemical composition MeFe2O4, (Me = Co, Zn, Ni) are of interest due to their electronic, magnetic and optical properties. Nanosized Co-Zr-Mn spinel ferrites with nominal composition CoFe2-2xZrxMnxO4 (0.1≤ x≤0.4) have been prepared by the co-precipitation route. The products are characterized by X-ray diffraction, scanning electron microscopy (SEM) at room temperature, dc electrical resistivity as a function of temperature and dielectric parameters in the frequency range of 100 Hz to 3 MHz are also measured. The lattice constants agree with usual spinel ferrites. The particle size calculated from X-ray data by the Scherrer formula is in the range of 28-30 nm, while the average particle size varies from 15-25 nm obtained from the SEM measurements, X-ray density (Dx), Porosity (P) and bulk density (Dm) for all the samples are calculated. The dc electrical resistivity decreased with the rise in temperature for all the samples, showing a semiconductor like behavior. From the dc electrical resistivity the activation energy and drift mobility are determined. Both the drift mobility and activation energy increase with a rise in x. The dielectric constant, dielectric loss and ac electrical resistivity as a function of frequency are also reported. The low field ac magnetic susceptibility measurement showed that the ferrimagentic transition temperature is in the range of 439±5 K to 658±5 K.

Abstract: Mg-Co nano crystalline ferrites having general formula Mg1-xCoxFe2O4 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25) were prepared by co-precipitation method. X-ray powder diffraction (XRD) patterns of the prepared samples show the formation single spinel phase. The crystallite size, lattice parameters and porosity of samples were calculated by XRD data analysis as function of cobalt concentration. The crystallite size for each sample was calculated using the Scherrer formula considering the most intense (3 1 1) peak lies in the range 27-35 nm. The lattice parameters increased with increase of cobalt concentration. It is because of the fact that cobalt has greater ionic radius then magnesium. The dielectric constant, dielectric loss tangent and ac electrical conductivity of the prepared samples is also measure. The observed variation in electrical and dielectric properties is explained on the basis of cations distribution among tetrahedral (A) and octahedral (B) sites. The variance in saturation magnetization, remanence magnetization and magnetic moment was also measured from BH curve of samples.