γ-Fe2O3/SiO2 nanocomposites for magneto-optical applications: Nanostructural and magnetic properties

Monolithic nanocomposites consisting in γ-Fe2O3 (maghemite) nanoparticles embedded in a silica gel have been prepared as potential magneto-optic materials, suitable for magnetic field sensing. The effects of several processing parameters on the structural and magnetic properties of the samples were evaluated to optimize their performance. Their structural properties have been studied by means of X-ray diffraction, thermogravimetric analysis and transmission electron microscopy, while the magnetic behavior has been characterized by Mössbauer spectroscopy and Faraday magnetometry. Our results indicate that maghemite crystallization conditions must be carefully controlled to obtain nanoparticles of an adequate size and to avoid subsequent evolution to other undesired ferric oxide phases.