Epitaxial layers of iron oxides have been grown on a MgO(001) substrate by evaporating natural Fe or 57Fe from Knudsen cells in the presence of a NO flow directed to the substrate. The resulting layers have been investigated in situ with LEED, RHEED, AES and XPS and ex situ with CEMS and ion beam analysis. For substrate temperatures between 200 and 400°C we observe RHEED oscillations during deposition, indicative of layer-by-layer growth. By adjusting the flux of NO at the surface, all stable and mctastable cubic phases in the Fe-O system could be grown: FeO (wustite), Fe O (magnetite), γ-Fe O (maghcmitc) and solid solutions between the latter two phases. Rutherford backscattering spectra show a relatively high minimum yield in the channel directions. © J.C. Baltzer AG, Science Publishers. 2 2 3 4 2 3