Effect of manganese substitution on the structural and magnetic properties of nanocrystalline lithium-zinc-manganese ferrites

Abstract

Structural and magnetic properties of mixed ferrite with nominal compositions Li0.2Zn0.6-xMnxFe2.2O4 ranging from x = 0.00 to 0.60 have been synthesized by auto combustion technique. Disk- and toroid-shaped samples prepared from these powders are sintered at various temperatures (1050 - 1250C). The optimum sintering temperature, Ts, for various compositions were selected based on maximum bulk density. Detailed investigations were carried out only for the sample sintered at optimum Ts. The X-ray diffraction patterns confirm that the sample forms cubic spinel structure for Mn content up to x = 0.30. Beyond these values of x, major phase of the composition is cubic spinel along with minor impurity phases -Fe2O3 and Mn3Li2O8 for x  0.40 which influenced the structural, electric and magnetic behavior of ferrites. Surface morphological investigation shows that average grain size significantly depends on Mn substitution. The initial permeability, relative quality factor, saturation magnetization increases with increasing Mn content up to x = 0.30. The dielectric constant and dielectric loss show dispersion in the low frequency range. AC conductivity shows frequency independent behavior at lower frequency region and increases with increasing the frequency. Complex impedance spectra have been studied in the frequency range 20 Hz to 10 MHz. The value of real part of complex impedance decreases with increasing frequency up to 105 Hz, and beyond this it becomes frequency independent.