Biocompatible superparamagnetic iron oxide nanoparticles used for contrast agents: a structural and magnetic study - Gamarra, Lionel Fernel; Brito, Giancarlo Espósito de Souza; Pontuschka, Walter Maigon; Amaro, E; Parma, A H C; Goya, Gerardo Fabían (Journal of Magnetism and Magnetic Materials, 2005)