Structural and magnetic susceptibility studies of SiO2: Fe2O3 nano-composites prepared by sol-gel technique

The samples show low-magnetic susceptibility χT value typical to anti-ferromagnetic substances at lower sintering temperature ranging from 200 up to 700 °C, while transition to ferrimagnetic behavior is observed at higher sintering temperature ranging from 700 up to 1150 °C. It is clearly seen that between 700 and 900 °C, a broad transition occurs from anti-ferromagnetic amorphous phase to a ferrimagnetic one, corresponding to γ-Fe2O3. At constant sintering temperature 1150 °C the samples show lower magnetic susceptibility χT value at higher concentrations of Fe2O3 embedded in silica gel matrix. The observed behavior can be explained by the presence of γ-Fe2O3, whose contribution to the magnetic saturation at higher Fe2O3 content is much lower than that of α-Fe2O3 (and/or ε-Fe2O3) at this higher temperature.