Stoichiometry and Magnetic Properties of Iron Oxide Films

Abstract

ABSTRACTThe stoichiometry, structural and magnetic properties, and Mössbauer spectra of reactively sputtered Fe-O films were studied as a function of the O2 partial pressure during the deposition. By increasing the amount of O2 films with the following crystallographic structures and stoichiometry were fabricated; amorphous Fe-O, mixture of Fe and FeO, offstoichiometric single-phase FexO, mixture of FeO and Fe3O4, single-phase Fe3O4, mixture of Fe3O4 and γ-Fe2O3, mixture of Fe3O4 and α-Fe2O3, and single-phase α-Fe2O3. The Verwey transition in Fe3O4 films was observed in the coercivity versus temperature curve and in the thermomagnetic data. FeO and α-Fe2O3 films showed anomalous ferromagnetic-like behavior, in contrast to their anti ferromagnetic nature in bulk. The unusual magnetic properties were attributed to the formation of clusters of tetrahedraly coordinated Fe3+ ions in FeO and to uncompensated surface spins, in α - Fe2O3 films.