Magnetic properties of sputtered Fe1-xO and Fe+Fe3O4 thin films

An attempt was made to increase saturation magnetization of Fe3O4 films by incorporating alpha-Fe phase through the decomposition of as-deposited Fe1-xO films, which were de-sputtered onto Si(100) substrate by controlling the oxygen flow rates to a thickness of 70-400 nm. The as-prepared Fe1-xO films, being ferrimagnetic, show a thickness dependent microstructure and properties. The formation region of the single phase Fe1-xO was worked out as functions of oxygen flow rate and thickness. After vacuum-annealing, the Fe1-xO phase decomposed to Fe+Fe3O4 phases leading to an increase in coercivity from 15 Oe to 520-990 Oe, and an increase in saturation magnetization from 100 to 290-410 emu/cm(3) depending on film thickness. The nanostructure of as-prepared and annealed films were examined by a high resolution transmission electron microscope, the former does not show well defined grain boundaries, while the later has well defined grains, 20-50 nm in size. (C) 1997 American Institute of Physics.