Magnetic properties of Ti-doped ultrafine CoFe2O4 powder grown by the sol gel method

Ultrafine Ti-doped CoFe2O4 powders, Ti0.2Co1.2Fe1.6O4, are fabricated by the sol gel method and their magnetic and crystallographic properties depending on annealing temperature are investigated by X-ray diffractometer, Mossbauer spectroscopy, and a vibrating sample magnetometer. With X-ray diffraction and Mossbauer spectroscopy measurements, the formation of nanocrystallized particles is confirmed when Ti0.2Co1.2Fe1.6O4 ferrite is annealed at 473 K. The samples annealed between 673 and 773 K, show that the ferrimagnetic phase and paramagnetic phase coexist. That is, the sample annealed at 673 K has the 18% ferrimagnetic phase, and the sample annealed at 773 K has the 88% ferrimagnetic phase. But the samples annealed at and above 873 K have only a single-phase spinel structure and behave ferrimagnetically. The Neel temperature of our sample is 643 K, which is lower than that of pure cobalt ferrite powder. The magnetic behaviour of Ti0.2Co1.2Fe1.6O4 powder shows that an increase in the annealing temperature yields a decrease in the coercivity and, in contrast, an increase in the saturation magnetization. The maximum coercivity and the saturation magnetization of Ti0.2Co1.2Fe1.6O4 ferrite powder are 1.56 kOe and 62.6 emu/g, respectively.