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

A single precursor technique was used to synthesize $γ-Fe2O3$ nanoparticles with diameters from 5 to 7 nm. The blocking temperature of the nanoparticles essentially increases with Fe precursor concentration. Transmission Mössbauer spectroscopy of the different $γ-Fe2O3$ 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 $γ-Fe2O3$ spinel structure vary with Fe concentration as well.