Preparation and magnetic properties of Fe-N thin films by the plasma evaporation method

The saturation magnetization, M_s, of films evaporated in an N₂ atmosphere and in N₂ plasma was investigated. Films deposited by evaporation in an N₂ atmosphere using an alumina crucible as the evaporation source had nearly the same M_s value (approximately 210/g) as pure Fe and were found by X-ray diffraction to contain no iron nitrides. The N, N₂⁺, and N₂*, were produced by plasma evaporation, an electron beam from an E-gun, and catalysis on a tungsten filament. The N, N₂⁺, or N₂* is necessary to obtain Fe-N films. The M_s of these films, which were deposited in a weak plasma and at a low deposition rate, increased with decreasing film thickness. The high-moment phase Fe₁₆N₂ could be produced when low density N, N₂⁺, and N₂* existed in the reactive gas atmosphere and when the film thickness was smaller than about 500 angstrom.