Magnetic and structural properties of γ-Fe2O3 nanoparticles dispersed in a silica matrix

Using ferric chloride and tetraethylorthosilicate (TEOS) as precursors, acetic acid and isopropyl alcohol as additives, and ethyl alcohol as solvent, Fe2O3:SiO2(30 divided by 70 %; 70 divided by 30 % molar ratio)- EtOH:TEOS:H2O (17.5:1:16 molar ratio) xerogels were prepared. Fe2O3 nanoparticles formation in amorphous SiO2 by xerogel. annealing at 100 degreesC, 200 degreesC, 900 degreesC and 1100 degreesC is presented. The samples were examined by X-ray diffraction (XRD), infrared spectrometry (IRS) and de magnetic measurements. Ferrimagnetic phase accurs after 900 degreesC heating; superparamagnetic behavior was observed after 200 degreesC heating and amorphous antiferromagnetic Fe2O3 phase was found after 100 degreesC heating. The increase of Fe ions leads to larger particle dimensions and the annealing temperature is decisive in different Fe2O3 phases formation.