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 °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 °C. 57Fe Mossbauer spectra, M − H curves and FC and ZFC curves demonstrated that the as-prepared nanoparticles presented superparamagnetic behavior at 27 °C and ferromagnetic behavior at −268 °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.