Structural and magnetic studies of Fe2O3 /SiO2 granular nanocomposites

G. POZO LÓPEZ; S. P. SILVETTI; A. F. CABRERA; A. M. CONDÓ

Comisión Nacional de Energía Atómica. San Martín, Pcia. de Buenos Aires, Argentina

Congreso; At the Frontiers of Condensed Matter IV: Current Trends and Novel Materials.; 2008

Centro Atómico Constituyentes - Comisión Nacional de Energía Atómica

Fe2O3/SiO2 nanocomposites were synthesized by mechanical alloying, using Fe and SiO2 powders as precursors. After 340 h milling, the sample essentially consists of hematite and amorphous silica. TEM images show hematite particles embedded in and surrounded by an amorphous silica matrix. A broad size distribution—5–50 nm—of hematite particles is found, and other group of very small —2–3 nm— unidentified particles are observed. Room temperature Mössbauer spectra show a paramagnetic doublet, which may correspond to a non-crystalline phase in the sample (probably the small unidentified particles), and a sextet corresponding to hematite. Magnetic properties were investigated by measuring hysteresis curves at different temperatures (5–300 K) and by zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves (10 mT). The hysteresis loops were well fitted by a ferromagnetic contribution. No evidence of Morin transition is found down to 5 K.