Crystallographic and magnetic properties of nanostructured hematite synthesized by the sol-gel process

Abstract

The results for the macroscopic magnetic properties for the sample mean, though further studies must be done,the possibility of some vacancies existing in the spin sublattice of the crystal values of the coercivity of the samples increased with increasing heat-treatment temperature and were much lower than that of bulk hematite. The magnetic properties of nanostructured hematite synthesized by using the sol-gel process was studied by using the methods of X-ray diffraction at room temperature, Mossbauer spectroscopy at various temperatures and hysteresis measurements by using vibrating sample magnetometer within the temperature range of 10 similar to 300 K. The samples prepared by using a chemical reaction were calcined at different temperature of 100 degreesC, 140 degreesC, 180 degreesC, 220 degreesC; and 350 degreesC for four hours. The X-ray diffraction patterns showed that the samples were in a single crystal phase, except that a little bit of the crystal phase of Fe appeared for the samples calcined at a temperatures of 100 degreesC: 140 degreesC, and 180 degreesC. The Mossbauer result indicated that the sample calcined at 100 degreesC was in a weak ferromagnetic phase within the measured temperature range. The particle size of the sample calcined at 100 degreesC was determined to be about 4 nm which is good agreement with the value obtained by using the universal Langevin function to analyze the temperature dependence of the magnetization. Also, the Debye model and spinwave theory were applied to the temperature dependence of the Mossbauer parameters for the nanostructured sample calcined at 100 degreesC and for bulk hematite.