Thermomagnetic and Mössbauer characterization of Iron Oxide Nanoparticles

C. E. RODRÍGUEZ TORRES, M. B. FERNÁNDEZ VAN RAAP, F. H. SÁNCHEZ,J. C. APHESTEGUY, S. E. JACOBO

JOURNAL OF ALLOYS AND COMPOUNDS

Elsevier

Año: 2009

0925-8388

Fe oxide particles were studied by thermomagnetogravimetry and Mössbauer effectspectroscopy, aiming to improve phase composition determination, which has been proven to bedifficult for these nanoscale materials. Nanoparticles were sinthetized by the coprecipitationroute in aqueous media using an initial molar ratio Fe3+:Fe2+ of 1.5:1 instead of the theoreticalone of 2:1, in order to compensate for the potential oxidation of Fe2+ during the preparationprocedure. The main feature present in the nanoparticles magnetic response is coincident withthe main feature observed in commercial partially oxidized magnetite. Mössbauer effect spectraindicate that magnetite contribution to the nanophase composition is at most 15 at.%. It isconcluded that nanoparticles are not homogeneous but a mixture or solid solution of spinel-typephases, most probably enriched in magnetite at the particle center and in maghemite at theparticle surface, due to surface higher oxidation ability.