Cation Distribution Assisted Tuning of Magnetization in Nanosized Magnesium Ferrite

The MgFe2O4 nanoparticles are synthesized by combustion method and annealed at different temperatures from 500 to 1000 degrees C. Magnetic properties, morphology, valence states of iron, crystal structure, and microstructure of the samples are investigated systematically by vibrating sample magnetometer, field emission scanning electron microscope, transmission electron microscopy, X-ray absorption spectroscopy, and synchrotron X-ray diffraction. Cation distribution is determined from synchrotron X-ray diffraction data using Rietveld refinement combined with extended X-ray absorption fine structure spectroscopy. The results indicates that all the samples are phase-pure with crystallite size ranging from 11 to 41nm. By adjusting the annealing temperature, cation distribution and particle size can be changed, and consequently leading to the change in structure and magnetic properties. The saturation magnetization of the samples are enhanced significantly compared to that of the bulk material. The variation of magnetic properties is discussed based on cation distribution, particle size, valence state, surface effect, and spin canting.