Magnetization and Mössbauer study of cobalt ferrite particles from nanophase cobalt iron carbonate

Nanosize CoFe 2O 4 particles prepared by a microemulsion method have been investigated by X-ray diffractometry, transmission electron microscopy, SQUID magnetometry and Mössbauer spectroscopy. All peaks of X-ray diffraction patterns can be attributed to a cubic spinel structure with the lattice constant a 0=8.397 Å. The average size of the particles, determined by transmission electron microscopy, is 49 Å. The coercivity and the maximal magnetization measured at 5 K in an applied magnetic field of 50 kOe are 15.1 kOe and 15.2 emu/g, respectively. In the same field of 50 kOe, the measured blocking temperature is about 35 K. Superparamagnetic behavior of these particles around room temperature is confirmed by the coincidence of the magnetization ( M) vs. an applied magnetic field ( H/ T) plots for different temperatures and the Mössbauer spectra.