X-ray, magnetic and differential thermal analysis and thermogravimetric (DTA-TG) measurements of Fe2O3 nanoparticles surrounded by amorphous SiO2were carried out. The mass loss above 370 K could be attributed to the dehydration. The broadened exothermic peak around 900
K was observed by the DTA analysis. Considering the results of the X-ray and magnetic analyses, this anomaly was interpreted
as due to the g- to a-transition in the present Fe2O3nanoparticle system. The broadness of the peak and thus the gradual progress of the transformation would be attributed to
the stress caused by the amorphous SiO2 network surrounding extremely small particles.