There is a strong interest in obtaining epitaxial layers of the α ′′ and γ ′ nitride phases of iron, because of their special ferromagnetic properties. The fact that these nitrides have a small fcc or bcc unit cell allows epitaxial growth without domain formation in contrast to the case of, for instance, Fe 3 O 4 . We tried three different routes to grow epitaxial iron nitride layers on MgO(001). The substrate temperature was varied between 150°C and 300°C in all cases. We found that it is impossible to grow nitride layers using a gas flow of mixtures of NH 3 , N 2 and H 2 as a nitrogen source, as was reported by a group of Hitachi. Only if this flow is led over a hot (1000–1200°C) iron surface, the formation of nitrides is observed. The nitrides were successfully grown using a home-built radio frequency atomic nitrogen source. The phases and structures of the layers were investigated with RBS, Mössbauer spectroscopy, X-ray diffraction and elastic recoil detection. It was observed that the presence of H 2 and the substrate temperature during growth are crucial to obtain epitaxial layers of γ ′ iron nitride. A mono-crystalline layer of γ ′ was grown directly on a MgO substrate at a temperature of 200°C. A highly disordered (amorphous) ε-like layer was grown at room temperature of a MgO substrate.