Surfactant-assisted synthesis and magnetic properties of monodispersed manganese ferrite nanocrystals

Monodispersed manganese ferrite (MnFe(2)O(4)) nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which octadecene was used as solvent, and oleic acid and oleylamine were used as capping ligands. MnFe(2)O(4) nanocrystals were obtained with size in a tunable range of 4-15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants. The phase structure, morphology, and size of the products were characterized in detail by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Magnetic properties of MnFe(2)O(4) nanocrystals with different morphologies were measured using a superconducting quantum interference device (SQUID). Both monodisperse MnFe(2)O(4) nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K. The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.