Formation of a non-magnetic metallic iron nitride layer on bcc Fe(100)

We report the formation of a stable iron nitride thin film following the exposition of an Fe(001) single crystal to atomic N plasma produced by means of a radio-frequency (rf) discharge source. The obtained phase, enabled by N-atomic diffusion into the iron matrix, has been characterized using spectroscopical and structural techniques. The comparison of the experimental results with first-principles calculations sheds light on the formed structure stability. The result is the formation of a metallic non-magnetic protective coating film on the iron substrate with a zinc blende (ZB) structure (γ''-FeN). The formed film has high oxidation resistance, metallic character, non-magnetic ground state and good epitaxial growth. Thermal treatment of the iron nitride film shows that, at around 700 K, the FeN is decomposed, resulting in bcc Fe as a consequence of the high diffusivity of N in Fe.