On the growth of magnetic Fe4N films

Magnetic epitaxial films of Fe4N have been grown by MBE in a flow of atomic nitrogen from a radio-frequency plasma source. Various mixtures of nitrogen and hydrogen have been used in the source during evaporation of 57Fe on a MgO(1 0 0) substrate. The admixture of hydrogen leads to an increase of the uptake of nitrogen by iron and it improves the crystalline properties of the films grown. It was found that the increased nitrogen uptake is due to a higher fraction of atomic N in the output of the source plus transport system. The sticking coefficient of N atoms to an iron and a Fe4N surface was found to be equal to unity under the conditions we used. The composition and the morphology of the films was studied with conversion electron Mِssbauer spectroscopy, X-ray diffraction, RBS/channeling and atomic force microscopy measurements. The results obtained clarify in part the growth mechanism of the iron nitride layers and the influence of hydrogen.