Preparation of magnetic nanoparticles (/spl gamma/-Fe/sub 2/O/sub 3/) in the silica matrix

Nanoparticles /spl gamma/-Fe/sub 2/O/sub 3/ were prepared in silica matrix by the sol-gel process. Conventional acid hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) were used for the preparation of porous silica matrix. Iron(III) nitrate was homogeneously dissolved in the initial TEOS solution. After gelification and drying, the xerogel was heat treated on the air at different temperature between 700-900/spl deg/C. The heating products were studied by high resolution TEM and magnetic measurements. Monocrystalline nanoparticles of /spl gamma/-Fe/sub 2/O/sub 3/ of size ranging between 50-100 /spl Aring/ were observed by HR TEM in the sample heated at 900/spl deg/C. Room temperature magnetic measurements show a weak ferrimagnetic component for samples heated until 880/spl deg/C, but a ferrimagnetic behaviour is evident at 4 K. The samples heated at higher temperature show ferrimagnetic behaviour at room temperature.<
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