Modèle pour la structure électronique des composés perovskites du manganèse 01/1975; DOI: 10.1051/jphys:0197500360120131700

ABSTRACT A theoretical model is proposed which could explain the magnetic and structural phase transitions which have been observed in perovskite compounds MMn 3X (M = metal, X = N or C). By applying the tight binding approximation to d électrons of Mn and p électrons of N, we find a sharp singularity in the electronic density of states at the Fermi level. This singularity could explain the nature of the magnetic phase transition, and the anormal behaviour of the susceptibility in the paramagnetic phase. The structural phase transition would be produced by a Jahn Teller type of effect. Nous proposons un modèle théorique qui semble pouvoir expliquer les transitions de phase magnétiques et cristallines observées dans les composés perovskites du type MMn3X (M = métal, X = N ou C). En appliquant l'approximation des liaisons fortes aux électrons d du manganèse et aux électrons p de l'azote, nous trouvons une forte singularité dans la densité d'états électroniques au niveau de Fermi. L'existence de cette singularité peut expliquer la nature des transitions magnétiques et le comportement anormal de la susceptibilité dans la phase paramagnétique. Le changement de phase cubique → tétragonale est alors attribué à un effet Jahn Teller sur la structure de bande.

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