Investigation of Cation and Cation Vacancy Distributions in the Zinc Substituted Maghemite, Prepared by One Pot Room Temperature Co-precipitation Method

From Low to High Saturation Magnetization in Magnetite Nanoparticles: The Crucial Role of the Molar Ratios Between the Chemicals

“…Magnetite ( ), in its bulk state, has a cubic inverse spinel structure with a lattice parameter of 8.39 Å, wherein all the divalent cations occupy octahedral sites and trivalent irons are equally distributed into octahedral and tetrahedral sites . On the other hand, in maghemite ( ), with a lattice parameter of 8.34 Å, all the cations are trivalent irons, and the compensation of Fe 2+ oxidation happens through the occurrence of the vacancies in its structure. , In both structures, the antiferromagnetic (superexchange interaction) coupling between the cations in octahedral and tetrahedral sites occurs through oxygen anions, and the net magnetic moment originates from the difference between the number of spins in these two sublattices. However, because of the vacancies in maghemite and the difference between the arrangement of cations in octahedral and tetrahedral sites, theoretical calculations for stoichiometric bulk samples indicate that the magnetic moment per unit formula of magnetite (4 Bohr magnetons, μ Β ) is larger than that of maghemite (2.5 μ Β ) .…”