Suppression of α-Fe2O3 Phase in MgFe2O4 Nanoparticles with High Magnetization by Controlling Annealing Process

We report the phase stability, microstructure and magnetic properties of MgFe2O4 nanoparticles under different annealing conditions. Magnetic properties of MgFe2O4 are strongly influenced by the crystal structure and morphology, which in turn, depend on annealing conditions. The as-prepared and samples annealed at 1200 degrees C show a pure spinel phase. Whereas the samples annealed and quenched at 600 degrees C-1000 degrees C exhibit the spinel phase along with a small fraction of the secondary phase of alpha-Fe2O3, which causes deterioration of magnetic properties. On the other hand, samples annealed at 600 degrees C-1000 degrees C under Argon atmosphere display superior magnetic properties (M = 44-56 emu/g at room temperature) due to the presence of pure spinet phase. Interestingly, the sample quenched at 1200 degrees C exhibits large saturation magnetization, M s = 63 emu/g at 5 K which is arising from the optimum cationic distribution (delta = 0.77) grown at elevated temperature is retained in the rapid cooling process.