LAUSR

A set of Sm-doped iron oxide magnetic nanoparticles (FexOy NPs) of different sizes as an example of ferromagnetic NPs at room temperature was synthesized by microware-assisted methods. Powder X-ray diffraction and transmission electron microscopy showed FexOy NPs with an inverse spinel structure. Mossbauer and X-ray absorption spectroscopy (XAS) were used to study the local atomic and electronic structure of iron in the NPs. Linear combination of XAS spectra of reference iron oxides failed in reproducing the spectra of FexOy NPs [Piquer, C.; J. Phys. Chem. C 2014, 118, 1332−1346]. We attribute this fact to the nonstoichiometric distribution of tetrahedral, Td3+, and octahedral, Oh3+ and Oh2+, sites in NPs compared to bulk references. This distribution was successfully reproduced by linear combination of theoretical XAS spectra obtained for clusters where iron was in Td3+, Oh3+, and Oh2+ defined oxidation and symmetry states. This approach allowed us to obtain the quantitative speciation of the fraction of...