MÖSSBAUER AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF DIFFERENT SIZE Fe3O4 NANOSTRUCTURE

Abstract

We examine size-dependent structural and magnetic properties of fine size controlled iron oxide nanoparticles in the 4–17 nm range confirmed by XRD. Through Mössbauer spectra, we found that the ratio of Fe 3+/ Fe +2.5 and the Fe vacancies on the B sites can be modified by varying the particle size. Coating Fe 3 O 4 nanoparticles with SiO 2 effectively eliminates magnetic interparticle interactions so that the Curie temperature (Tc) can be well fitted by an expression for noninteracting randomly oriented single-domain nanoparticles. The Tc of the samples was 746–849 K lower than that of the bulk material, which may be related to a nanequilibrium cation distribution. The results are discussed in terms of interparticle interactions.