Hybrid magnetic nanoparticles derived from wüstite disproportionation reactions at the nanoscale

We present Mossbauer studies of hybrid iron-oxide nanoparticles obtained by the disproportionation of oleic acid stabilized wustite (FexO) nanoparticles produced by selective oxidation of iron pentacarbonyl in high boiling temperature organic solvents. The results support X-ray diffraction and Transmission Electron Microscope studies of the presence of mixed FexO and Fe3O4 phases within the nanoparticles whose relative content can be altered through heat treatment in nitrogen atmosphere. Furthermore, the Mossbauer study gives evidence of the presence of an amorphous, spin-glass like phase due to spin frustration at the FexO/Fe3O4 interface.