Nanophase magnetic materials: Synthesis and properties

Self-assembly preparative techniques in confined media that lead to magnetic materials with nanometer dimensions are described. Synthesis of nanoparticles using the restricted environments offered by surfactant systems such as water-in-oil microemulsions (reverse micelles) provide excellent control over particle size, inter-particle spacing, and particle shape. These environments have been used in the synthesis of gamma-Fe2O3 Fe3O4, MnFe2O4, CoFe2O4, Fe and Fe/Au with particle sizes ranging from 10-20 nm. The controlled environment of the reverse micelle also allows sequential synthesis, which can produce a core-shell type structure (e.g., iron nanoparticles with gold coatings). Lyotropic liquid crystal media also offer template effects for the synthesis of non-spherical magnetic nanostructures. The structures, theory and modeling concepts and novel physical properties of these materials are discussed with emphasis given to the differences between course and fine grained magnetic materials.