Room-temperature soft magnetic iron oxide nanocrystals: Synthesis, characterization, and size-dependent magnetic properties

Monodisperse faceted and cubic magnetite nanoparticles were synthesized by the reduction of iron (III) acetylacetonate (Fe(acac)3) with N-methylpyrrole or pyrrole in the presence of the surfactants oleic acid and oleylamine in air. Particle size control can be attained by careful adjustment of the concentrations of the reactants and the surfactants. We also obtained monodisperse maghemite nanoparticles by the oxidation of the as-prepared Fe3O4 nanoparticles. The magnetic studies exhibit that increasing the size of iron oxides nanoparticles leads to the enhanced magnetic properties. In particular, the iron oxides nanoparticles with size more than 5 nm are soft ferromagnetic at room temperature.