1. Mangetization study of nanosize $CoFe_2O_4$ particles prepared by a microemulsion method
Nanophase cobalt iron hydroxide carbonate complex was synthesized in an inverse microemulsion system. The complex was used as a precursor to make cobalt ferrite. The average size of cobalt ferrite particle can be controlled by the ratio $R = [H_2O]/[AOT]$ and showed the range of 3.8 to 6.5 nm. The characteristics of the final ferrite paricles were investigated using X-ray diffractometer(XRD), transmission electron microscope(TEM), and energy dispersive x-ray spectrometer(EDX).
The magnetic properties of the particle were also measured with a superconducting quantum interference device (SQUID) magnetometer. The saturation magnetization was increased with the particle size. The ferrite sample with the average particle size of 6.5 nm showed the largest saturation mangetization of 31.7 emu/g.
2. Magnetization and M&Oumi;ssbauer 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 M&Oumi;ssbauer 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 is 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) versus an applied magnetic field (H/T) plots for different temperatures and the M&Oumi;ssbauer spectra.
3. Structure and magnetic properties of partially-inverted zinc ferrite particles
Ultrafine powders of Zn-ferrite with an ave...