Direct synthesis of highly crystalline and monodisperse manganese ferrite nanocrystals

Highly crystalline and monodisperse manganese ferrite nanocrystals were synthesized via the thermal decomposition of metal-surfactant complexes followed by mild chemical oxidation. Particle sizes could be varied from 5 to 13 nm by changing the experimental parameters. The uniformity of the nanocrystals was demonstrated by the formation of two- and three-dimensional superlattices. Electron diffraction, X-ray diffraction, and high-resolution TEM images confirmed the high crystallinity of the manganese ferrite nanocrystals. Elemental analysis and energy-dispersive X-ray spectroscopy confirmed that the molar ratio of Mn:Fe was 1:2. The nanocrystals were found to exhibit the typical behaviors of magnetic nanocrystals with the characteristic narrow energy barrier distributions of magnetic anisotropy, confirming the uniformity of the nanocrystals.