IMPACT OF CHROMIUM DOPING ON STRUCTURAL, OPTICAL, MAGNETIC AND ELECTRICAL PROPERTIES OF NANO-COPPER FERRITE

Abstract

Nanoparticles copper ferrites doped with chromium CuCrxFe2- xO4 (0≤x≤ 0.25) were prepared using sol-gel auto combustion. Analysis of XRD revealed that the samples crystallized in single phase tetragonal CuFe2O4 structure. Results of Rietveld refinement using Full proff program showed that the lattice parameter a increased, lattice parameter c, the unit cell volume and tetragonal distortion decreased with increasing Cr3+ concentration. A cation distribution ensured that a system (CuCrFeO4) is completely inverse and distorted. In addition, crystallite size increased with the increase of Cr3+content.Furthermore, optical energy band gap of the obtained spinel ferrite decreased from 2.441eV to 2.228 eV with the increase of Cr. Results of magnetic properties indicated that the saturation magnetization decreased from 24.1 to18.3 emu/g with Cr increment, due to a lower magnetic moment of Cr3+ ion (3mB) than that of Fe3+ ion (5mB).Coercivity decreases with increasing Cr-concentration can be attributed to the reduction in magnetocrystalline anisotropy (K) where, chromium ferrite has negative magnetocrystalline anisotropy. Squareness ratio decreased continuously with Cr content, which it displayed that the materials exhibited to soft magnetic properties. Dielectric properties were analyzed in frequency range (0.1-7MHz) at different temperatures (50- 150ºC).From electrical measurements, it was found that έ decreased at lower frequency, become nearly constant at higher frequencies for all samples and increased with increasing temperature. έ was found to increase with increasing Cr because the Cr is reducing the hopping probabilities across the grain boundaries. . Also, it was found that activation energy ΔE decreased with increasing Cr concentration.