The structure-tunable synthesis and magnetic properties of Fe3O4 nanocrystals

Magnetite nanocrystals with tunable crystalline structures (orthorhombic and cubic) were synthesized via a simple oxidation-coprecipitation approach basing on the reaction of FeSO4·7H2O with C6H12N4. The average diameter of prepared orthorhombic Fe3O4 nanorods were 15 nm while their lengths were approximately 150~200 nm. As-prepared cubic counterparts were composed of 10 nm sized nanoparticles. XRD, FESEM, TEM, SAED and HRTEM were then used to characterize our samples. In addition, magnetic measurements showed the saturation magnetization of orthorhombic magnetite was lower than that of cubic ones. Mössbauer spectroscopy verified the samples possessed the nature of cubic magnetite. Finally, a possible growth mechanism for orthorhombic nanorods and cubic nanoparticles was also discussed.