pH control of magnetic properties in precipitation-hydrothermal-derived CoFe2O4

Cobalt ferrite nanoparticles (CFO NPs) were synthesized using precipitation followed by a hydrothermal treatment. The conditions for precipitation were kept constant, while the pH, the temperature and the synthesis time for the hydrothermal treatment were systematically varied. The results show that the pH plays the dominant role in the formation, growth and crystallization of the desired phase. Furthermore, by controlling the pH the magnetic properties, such as the magnetization and the coercivity of the CFO NPs, can be tuned. An increase in the temperature induced both particle growth and a change of the morphology. The variation of the synthesis time indicated that the hydrothermal reaction proceeds for up to 8 h; however, a further prolongation of the synthesis time does not affect the structural and magnetic properties to any significant extent.