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

Fe2O3/SiO2 nanocomposites were synthesized by mechanical alloying, using Fe and SiO2 powders as precursors. After 340 hours 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 to 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.2O3/SiO2 nanocomposites were synthesized by mechanical alloying, using Fe and SiO2 powders as precursors. After 340 hours 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 to 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.. 5 to 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.. 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.