  Bulk monolithic samples of {\gamma}-Fe2O3/SiO2 composites with different iron
oxide/silica ratios have been prepared by the sol-gel technique. Iron oxide
nanoparticles are obtained in-situ during heat treatment of samples and silica
matrix consolidation. Preparation method was previously optimized to minimize
the percentage of antiferromagnetic {\alpha}-Fe2O3 and parallelepipeds of
roughly 2x5x12 mm3, with good mechanical stability, are obtained. RT
magnetization curves show a non-hysteretic behavior. Thus, magnetization
measurements have been well fitted to an expression that combines the Langevin
equation with an additional linear term, indicating that some of the
nanoparticles are still superparamagnetic as confirmed by X-ray diffraction and
electron microscopy measurements. Zero field cooled /field cooled experiments
show curves with slightly different shapes, depending on the size and shape
distribution of nanoparticles for a given composition. Magneto-optical Faraday
effect measurements show that the Faraday rotation is proportional to
magnetization of the samples, as expected. As a demonstration of their sensing
possibilities, the relative intensity of polarized light, measured at 5{\deg}
from the extinction angle, was plotted versus applied magnetic field.
