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Interplay of Chemical Bonding and Magnetism in Fe_4N, Fe_3N, Fe_2N

M. Sifkovits·H. Smolinski·S. Hellwig·W. Weber
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Abstract

Using spin density functional theory we have carried out a comparative study of chemical bonding and magnetism in Fe_4N, Fe_3N and Fe_2N. All of these compounds form close packed Fe lattices, while N occupies octahedral interstitial positions. High spin fcc Fe and hypothetical FeN with rock salt structure have been included in our study as reference systems. We find strong, covalent Fe-N bonds as a result of a substantial σ-type p-d hybridisation, with some charge transfer to N. Those Fe d orbitals which contribute to the p-d bonds, do no longer participate in the exchange splitting of the Fe d bands. Because of the large exchange fields, the majority spin d bands are always fully occupied, while the minority spin d bands are close to half-filling, thus optimizing the Fe d-d covalent bonding. As a consequence, in good approximation the individual Fe moments decrease in steps of 0.5 μ_B from fcc iron (2.7 μ_B) via Fe_4N (2.7 and 1.97 mu_B}), \chem{Fe_3N} (1.99 μ_B) to ζ- Fe_2N (1.43 μ_B).

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M. Sifkovits, H. Smolinski, S. Hellwig, W. Weber. 1998-10-28. Interplay of Chemical Bonding and Magnetism in Fe_4N, Fe_3N, Fe_2N. https://doi.org/10.1016/s0304-8853(99)00296-6

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