Iron nitride films have been prepared by reactive DC magnetron sputtering. The composition of Fe1-xNx was varied over a range of 0 < x < 0.5 by controlling the nitrogen flow rate during sputtering. These films were characterized using powder X-ray diffraction (XRD), thermogravimetric and electron microprobe analysis. We found that the nitrogen content in the films increased with nitrogen gas partial pressure. XRD experiments revealed an evolution through the alpha-Fe, y '-Fe4N, epsilon-Fe2+zN, xi-Fe2N, y '''-FeN and -y ''-FeN phases, when the nitrogen gas mole percentage was increased from 0% up to 70%. Above 70%, only the y '''-FeN phase was formed despite a measurable increase in the nitrogen content of the film with nitrogen gas partial pressure. Rietveld analysis of powder X-ray diffraction patterns revealed that this behavior is due to an increase in the nitrogen site occupation factor within the lattice. (c) 2005 Elsevier B.V. All rights reserved.