Preparation and size-dependent magnetism of highly dispersed iron silicide nanoparticles on silica

Fe3Si nanoparticles with a size of about 6-9 nm well dispersed on silica have been prepared by pyrolysis of ferrocene-polydimethylsilane composites at 600 degrees C. Powder XRD patterns, TEM and HRTEM images, and XPS spectra revealed that the average particle size increased with increasing pyrolysis temperature and a new phase, Fe5Si3, appeared when the pyrolysis temperature was above 800 degrees C. Fe-57 Mossbauer spectra, M - H curves and FC and ZFC curves demonstrated that the as-prepared nanoparticles presented superparamagnetic behavior at 27 degrees C and ferromagnetic behavior at -268 degrees C, and their particle sizes had a great impact on their magnetic properties. The Fe3Si nanoparticles on silica may find applications in magnetically recording materials, magnetically separable catalysts and electrode materials for spintronic devices.