Structural and magnetic properties of Co-substituted NiCu ferrite nanopowders

Abstract

Co-substituted NiCu ferrite nanopowders with the chemical formula Ni0.5−xCu0.5−xCo2xFe2O4 (0≤x≤0.50) were synthesized by sol-gel auto-combustion method. The effects of Co substitution on the cation distribution, structural and magnetic properties of the NiCu ferrite nanopowders have been investigated. Differential thermal analysis-thermogravimetry (DTA-TG), X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) measurements were used to characterize the chemical, structural and magnetic properties of the ferrite nanopowders, respectively. The DTA-TG results indicate that there are three steps of the combustion process. XRD results indicate that there are Fe2O3 and CuO impurity phases when x≤0.10. Furthermore, the lattice parameter increases, and the X-ray density and the average crystallite size decrease with increasing Co substitution. And the obtained particle size from TEM image is in very good agreement with the average crystallite size estimated by XRD measurements. The saturation magnetization and coercivity monotonically increase with the increase of Co substitution. The increase of the saturation magnetization is due to the substitution of Ni2+ and Cu2+ ions with lower magnetic moment by Co2+ ions with higher magnetic moment on the octahedral sites. And the increase of the coercivity is mainly due to the increase of magnetocrystalline anisotropy energy.