Improvement of microstructure, initial permeability, magnetization and dielectric properties of nanocrystalline LixCu0.1Co0.1Zn0.8−2xFe2+xO4

Abstract

Structural, magnetic and dielectric properties of Li substituted LixCu0.1Co0.1Zn0.8−2xFe2+xO4 (where x=0.00–0.40) prepared by auto combustion method have been investigated. The X-ray diffraction patterns of these compositions confirmed the formation of the single phase spinel structure. Disc- and toroid-shaped samples are prepared from each composition and sintered at various temperatures (1100–1300°C) in air for 1h. The lattice parameter decreases with the increase in Li1+ content obeying Vegard's law. The particle size of the starting powder compositions varied from 24 to 46nm. The bulk density and permeability increases up to a certain level of Li1+ substitution, beyond that all these properties decrease with increase in Li1+ content. The bulk density increases with increase in sintering temperatures up to 1150°C both for the parent and substituted compositions. Due to substitution of Li1+, the real part of the initial permeability increases from 18 to 61 for x=0.10 for the samples sintered at 1150°C. The ferrites with higher initial permeability have relatively lower resonance frequency which obey Snoek's law. The initial permeability strongly depends on average grain size and intragranular porosity but at higher sintering temperatures some voids are present in the samples which reduce the density and hence permeability of the samples. The ferri to paramagnetic transition temperature, TC, for the parent sample is below room temperature. The TC increases almost linearly with increasing Li content.The saturation magnetization, Ms, and the number of Bohr magneton, n(µB), increases up to x=0.30 due to the enhancement of the A–B interaction in the AB2O4 spinel type ferrites. Beyond that value of x, the Ms and the n (µB) values are decreased. The substitution of Li1+ influences the magnetic parameters due to modification of the cation distribution. Dielectric constant (ε′) decreases with increase in frequency which is rapid at lower frequencies and slower at higher frequencies which may be due to the Maxwell–Wagner interfacial polarization.