Synthesis of CoFe 2 O 4 nanoparticles with tunable magnetism by the modified hydrothermal method

Cobalt ferrite (CoFe2O4) nanoparticles were synthesized by using the hydrothermal route with the addition of trisodium citrate dihydrate (Na3CA·2H2O). The formation of CoFe2O4 nanoparticles with size ranging from 13 to 19 nm was confirmed by X-ray diffraction, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy; the clear-cut sharp of the nanoparticles was observed by transmission electron microscopy. By these characterization methods, the evolution of lattice constant and morphologies of the nanoparticles with the addition of Na3CA·2H2O is observed. Furthermore, the magnetic hysteresis loops measured at room temperature indicate that the magnetic properties of the products also show clear relationship with the masses of Na3CA·2H2O. For example, coercivity and high-field paramagnetic susceptibility increase with the increasing masses of Na3CA·2H2O, whereas the saturation magnetization and the effective magnetic anisotropy constant have the maximum values as the mass of Na3CA·2H2O is 1 g. This change of magnetic properties is related with the expanded lattice and the varied size and shape because of the addition of Na3CA·2H2O.