γ-Fe2O3 nanoparticle intrinsic magnetism dependence on iron-ion availability during synthesis

A single precursor technique was used to synthesize gamma-Fe2O3 nanoparticles with diameters from 5 to 7 nm. The blocking temperature of the nanoparticles essentially increases with Fe precursor concentration. Transmission Mossbauer spectroscopy of the different gamma-Fe2O3 nanoparticle systems reveal that the local Fe environments in the nanoparticle vary considerably with Fe precursor concentration. Not only does the nanoparticle size change, but the magnitude of the hyperfine field (a measure of the nanoparticle moment), the amount of chemical disorder in the nanoparticle, and the number of Fe moments in the octahedral and tetrahedral sites of the gamma-Fe2O3 spinel structure vary with Fe concentration as well. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3063076]