Enhancement of initial permeability and reduction of loss factor in Zn substituted nanocrystalline Li0.35−0.5xNi0.3ZnxFe2.35−0.5xO4

Abstract

Li-Ni-Zn ferrite nano-powders with nominal compositions of Li0.35−0.5xNi0.3ZnxFe2.35−0.5xO4 (x=0.00–0.40 in steps of 0.10) were synthesized by the chemical sol-gel auto combustion technique. Disk- and toroid-shaped samples prepared from each composition have been sintered at various temperatures (1373–1573K) for 5h. The internal structure was characterized by X-ray diffraction (XRD), which has confirmed the formation of single phase spinel structure. The crystallite size of the as grown powder varied from 23 to 37nm as measured using Scherrer formula. The lattice constant and theoretical density are found to increase with increasing Zn content. The Zn substitution acts as an accelerator of grain growth and uniform grain distribution in these compositions. The real part of initial permeability, relative quality factor and saturation magnetization increase with increasing Zn content for a fixed sintering temperature. As sintering temperatures increases porosity decreases, and initial permeability increases for the sample sintered up to1523K then decrease for further increasing temperature. The maximum value of μi/(=254) is observed for Li0.15Ni0.3Zn0.4Fe2.15O4 sintered at 1523K which is more than 6 times compared to that of parent composition. The loss factor for this composition is also reduced 6 times. As a result high relative quality factor is observed in these compositions. The weakening of exchange interaction may be confirmed by increasing the lattice parameter and decreasing Néel temperature (938–663K) as the increase of Zn content. Substitution of Zn influences the magnetic properties due to modification of cation distribution.