Study of Soft/Hard Bimagnetic CoFe²/CoFe²O⁴ Nanocomposite.

We report an experimental study of the bimagnetic nanocomposites CoFe₂/CoFe₂O₄. The precursor material, CoFe₂O₄ was prepared using the conventional stoichiometric combustion method. The nano-structured material CoFe₂/CoFe₂O₄ was obtained by total oxygen reduction of CoFe₂O₄ using a thermal treatment at 350 °C in H₂ atmospheres following the partial oxidation in O₂ atmospheres at 380 °C during 120; 30; 15, 10, and 5 min. The X-ray diffraction, Mössbauer spectroscopy and transmission electronic microscopy images confirmed the formation of the material CoFe₂/CoFe₂O₄. The magnetic hysteresis for the nanocomposite with different saturation magnetization (from 87 to 108 emu/g) also confirms the formation of the CoFe₂/CoFe₂O₄ with different content of CoFe₂O₄. Furthermore, the magnetic hysteresis curves for all samples presented a single magnetic behavior, suggesting the magnetic coupling between the phases of the nanocomposite. The effects of high energy milling on the magnetic properties of the precursor material and nanocomposites samples were evaluated.