Ferromagnetic resonance investigation of maghemite-silica nanocomposites

Maghemite-silica nanocomposites were prepared from water-based magnetic fluids through the sol-gel method. X-ray diffraction revealed that the maghemite nanoparticles had a size of 5 nm . Electron magnetic resonance of the composites was studied as a function of temperature and nanoparticle concentration. The resonance field was found to decrease upon increasing the maghemite concentration, while the linewidth increased. The effect was interpreted in terms of interparticle as well as intraparticle magnetic interactions. The data analysis suggests the presence of small agglomerates in the maghemite-silica nanocomposite for higher particle concentrations.