Effets chimiques et magnétovolumiques compétitifs dans les nitrures d'insertion

MATAR, Samir F.

doi:10.1016/S1631-0748(02)01410-8

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MATAR, Samir F.
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

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Ce document a été publié dans

Comptes Rendus. Chimie. 2002, vol. 5, n° 6-7, p. 539-546

Académie des sciences (Paris)

Résumé en anglais

An analysis of the chemical and magnetovolume effects due to nitrogen insertion is carried out in order to establish trends for the Fe-N system. Computations are based on the density functional theory and use is made of the augmented spherical wave method. Taking the Fe4N nitride as a representative member, the chemical bonding study shows that nitrogen selectively contracts covalent bond with one of the two iron sublattices, with the consequence of lowering the magnetic moment. The magnetovolume effects are examined for a comparative study of the volume-dependent magnetic moments within Fe4N as with respect to γ-Fe, in its two magnetic states 'high-moment-large volume' and 'low moment-low volume'. The insertion of nitrogen 'prepares' the volume in such a manner in the nitride that the two states are simultaneously present at the two Fe crystal sites. The trends for an increase of the Fe atomic volume within the series Fe8N, Fe4N, Fe3N, Fe2N should favour the enhancement of the magnetisation; this is, however, hindered by the Fe-N chemical bond, involving an increasing number of Fe sites leading to a lowering of the moments.< Réduire

Mots clés en anglais

Iron nitrides

Ferromagnetism

Density functional theory (DFT)

Local spin density approximation (LSDA)

Chemical bonding

Magnetovolume effects

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