Synthesis and characterization of cobalt ferrite nanoparticles prepared by the glycine-nitrate process

Abstract

In this research, microstructural evolution and magnetic properties of cobalt ferrite spinel (CoFe2O4) were studied. The ferrite was prepared by the glycine-nitrate process (GNP) followed by calcination process, and subsequent high energy mechanical milling. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and vibration sample magnetometery (VSM) methods. The results showed that the desired high purity spinel phase was formed through a complete combustion reaction using the G/N ratio of 1.48. The as-synthesized powder revealed the coercivity and saturation magnetization of 900 Oe and 62.83 emu/g, respectively. The CoFe2O4 phase was stable after calcination at 500 °C for 2 h under argon atmosphere and subsequent milling processes for 2 and 4 h. The highest coercivity value was obtained for the calcined sample (975 Oe), whose average particle size exhibited noticeable conformity with the single magnetic domain size of CoFe2O4 (~ 40 nm). For the 2 h-milled and 4 h-milled samples, the average particle size was below the single magnetic domain size, causing a significant reduction in coercivity values (820 and 770 Oe, respectively). The saturation magnetization was increased negligibly after the calcination process (63.22 emu/g), while it was raised to 71.47 and 73.98 emu/g after 2 and 4 h milling, probably due to the cationic redistribution during milling.