Matrix-Mediated Synthesis of Nanocrystalline γ-Fe2O3: A New Optically Transparent Magnetic Material

A new magnetic material with appreciable optical transmission in the visible region at room temperature has been isolated as a γ-Fe 2 O 3 /polymer nanocomposite. The synthesis is carried out in an ion-exchange resin at 60°C. Magnetization and susceptibility data demonstrate loading-dependent saturation moments as high as 46 electromagnetic units per gram and superparamagnetism for lower loadings where particle sizes are less than 100 angstroms. Optical absorption studies show that the small-particle form of γ-Fe 2 O 3 is considerably more transparent to visible light than the single-crystal form. The difference in absorption ranges from nearly an order of magnitude in the "red" spectral region to a factor of 3 at 5400 angstroms. The magnetization of the nanocomposite is greater by more than an order of magnitude than those of the strongest room-temperature transparent magnets, FeBO 3 and FeF 3 .