Magnetite and Other Fe-Oxide Nanoparticles

Magnetic NPs containing 3D transition metal oxides or relative mixtures are one of the most studied nanomaterials in view of their prospective, ubiquitous applications in quite different areas, the most important being biomedicine, sensor technology, and magnetic recording. According to their usage, magnetic NPs are often either embedded in a diamagnetic solid or dispersed in a fluid; in some cases they are surrounded by an outer shell of a diamagnetic material. The magnetic properties of nanoparticles (NPs) are quite different from those of the corresponding bulk material and a detailed subsection will analyze them in detail. In a simplified picture, an ideal magnetic NP can be figured out as provided of a highly symmetrical body (e.g., spherical, ellipsoid, acicular) and characterized by a homogeneous magnetization provided by the ferro- (or ferri-) magnetic alignment of elementary magnetic moments, giving rise to a mesoscopic permanent magnetic moment associated to the particle. Of course this picture can be improved to account for the role played by the NP surface, whose chemical and magnetic properties can be quite different from those at the particle core.