Shape-tuned synthesis of dispersed magnetite submicro particles with good magnetic properties

Sphere-like Fe₃O₄ submicro particles have been synthesized through a solvothermal route using FeCl₃ as the iron source, oleic acid as the surfactant and ethylene glycol as the reducing agent and solvent. Size ranging from ∼150 to ∼450 nm has been realized by controlling reaction time. Transformation of shape from spherical, porous spherical to polyhedral was demonstrated by adjusting the content of oleic acid. Room-temperature magnetization hysteresis loops show that the value of saturation magnetization increases from 57.8 to 72.4 emu/g and the corresponding coercive field increases from 44.3 to 93.5 Oe with increasing the grain size from ∼150 to ∼450 nm. Size-dependent magnetic properties of these sphere-like magnetite particles with high saturation magnetization and low coercive field may lead to new applications in biological fields.