Combustion synthesis of Co2+ substituted Li0.5Cr0.5Fe2O4 nano-powder: Physical and magnetic interactions

Nanocrystalline ferrite powders of Co2+ substituted Li0.5Cr0.5Fe2O4 were synthesized by sol-gel auto-combustion method. The samples were obtained by annealing at relatively low temperature at 600 degrees C and investigated by XRD, TEM, IR, magnetization, and dielectric and resistivity measurements. Lattice parameter, X-ray density, crystallite size and bulk density are found to increase, whereas specific surface area and porosity size showed the decreasing trend with the Co2+ substitution. Splitting of major absorption bands related to Li+ substituted ferrites was observed in IR spectra. Site occupancy is obtained from XRD and the variation of the cation distribution has been discussed on the basis of site preference of the substituting cations. Substitution of the magnetic Co2+ ions considerably improved the magnetic properties; as reflected by the advancement in the values of saturation magnetization and coercivity. The variation of the magneton number with the Co2+ content is satisfactorily explained on the basis of Neel's collinear spin ordering model. Resistivity plots show the semiconducting nature of the synthesized samples. The observed variation in resistivity is explained by Verwey hopping mechanism. The dielectric constant and dielectric loss tangent were also studied as a function of temperature. (C) 2014 Elsevier B.V. All rights reserved.