Annealing temperature dependent structural and magnetic properties of MnFe2O4 nanoparticles grown by sol-gel auto-combustion method

Manganese ferrite (MnFe2O4) nanoparticles were synthesized by sol-gel auto-combustion method using manganese nitrate and ferric nitrate as precursors and citric acid as a fuel. Scanning electron micrographs show irregularly shaped morphology of the particles. The as-prepared samples were annealed at 400, 500, 600 and 800 degrees C for 2 h in air. The phase identification and structural characterizations were performed using powder X-ray diffraction technique along with Mossbauer spectroscopy. Magnetization loops and Fe-57 Mossbauer spectra were measured at RT. After annealing the sample at or below similar to 500 degrees C, we observed two different spinel phases corresponding to two different lattice parameters. This is originating due to the partial oxidation of Mn2+ to Mn3+. At high annealing temperatures (similar to 600 degrees C or above) the spinel MnFe2O4 phase decomposes into crystalline alpha-Mn2O3 and alpha-Fe2O3 phases, and amorphous FeO phase. (c) 2017 Elsevier B.V. All rights reserved.