Effect of Surfactant on Magnetic and Optical Properties of α-Fe2O3 Nanoparticles

Hematite (alpha-Fe2O3) nanoparticles and hematite nanopaxticles coated with polyvinylpyrrolidone (PVP) are synthesized chemically by co-precipitation. Prolysis and microemulsion methods respectively. An average size of nanopaxticles (both coated and uncoated) was found by the broadening of the X-ray diffraction peaks using Scherrer's formula. It was found that coating reduced particle sizes. The attachment of the polymer on the surface of particles was confirmed by the Fourier transform infrared spectroscopy and thermogravimetric analysis. Optical ultraviolet/visible reflectance test also indicated the presence of PVP in coated nanohematites. In magnetic studies, it was observed that coating does not change main magnetic character of the alpha-Fe2O3 nanoparticles however it reduces DC magnetization (as a function of applied field and temperature) to a considerable amount. Moreover it was observed that after coating Morin transition temperature T-M and its width Delta T-M shifts to lower values, which is another indication of size reduction.