Low-Temperature Synthesis of Nanocrystalline Mn<sub>0.2</sub>Ni<sub>0.8</sub>Fe2O<sub>4</sub> by Oxalate Precursor Route

Abstract

Manganese nickel ferrite (Mn 0.2 Ni 0.8 Fe 2 O 4 ) powder was synthesized through oxalate precursor route. The effect of annealing temperature (400˚C -1100˚C) on the formation, crystalline size, morphology and magnetic properties was systematically studied. The resultant powders were investigated by thermal analyzer (TG-DTG-DSC), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Based on thermal analysis results, the oxalate mixture decomposed thermally in multisteps weight loss up to about 680˚C. XRD indicated that Mn 0.2 Ni 0.8 Fe 2 O 4 formed at much lower annealing temperature (≤400˚C) but contained α-Fe 2 O 3 impurity. The hematite phase decreased by increasing the annealing temperature. The lattice parameters were increased with increasing annealing temperature up to 1000˚C. The average crystalline size increased by increasing the annealing temperature. Single well crystalline ferrite was obtained at 800˚C with crystallite size about 109 nm. The saturation magnetization of the ferrites powders continuously increased with the increase in annealing temperature. Maximum saturation magnetization 48.2 emu/g was achieved for the formed Mn 0.2 Ni 0.8 Fe 2 O 4 phase at annealing temperature 1100˚C.