[Théorie ab initio de l'ordre multipolaire dans les dioxydes d'actinides]
Les transitions de phases magnétiques impliquant des degrés de liberté multipolaires ont été beaucoup étudiées au cours des vingt dernières années, remettant en question l'approximation usuelle selon laquelle les propriétés physiques d'un matériau magnétique pourraient être convenablement décrites par des degrés de liberté purement dipolaires. Les problèmes à résoudre sont compliqués à cause du grand nombre d'interactions concurrentes concernées. C'est pour cette raison que les dioxydes d'actinides, avec leur structure cristallographique simple (cubique à faces centrées), représentent une classe de composés idéale pour aborder l'étude des ordres multipolaires, tant du point de vue théorique qu'expérimental. Dans cet article, nous résumons nos tentatives récentes, qui visent à fournir une description ab initio des phases ordonnées des composés UO2, NpO2, et AmO2 au moyen de calculs avancés. Cette analyse systématique de la structure électronique est ici intrinsèquement reliée au champ cristallin local qui détermine la composition des états 5f des ions actinides. Corrélativement à ceux-ci, nous mettons en évidence le fait que les mécanismes qui conduisent aux états fondamentaux isolants, observés expérimentalement, agissent de manière clairement différente pour chacun des composés de la série.
Magnetic phase transitions that involve multipolar degrees of freedom have been widely studied during the last couple of decades, challenging the common approximation which assumes that the physical properties of a magnetic material could be effectively described by purely dipolar degrees of freedom. Due to the complexity of the problem and to the large number of competing interactions involved, the simple (fcc) crystal structure of the actinide dioxides made them the ideal playground system for such theoretical and experimental studies. In the present paper, we summarize our recent attempts to provide an ab initio description of the ordered phases of UO2, NpO2, and AmO2 by means of state-of-the-art first-principles calculations. This systematic analysis of the electronic structures is here naturally connected to the local crystalline fields of the 5f states in the actinide dioxide series. Related to these we find that the mechanisms which lead to the experimentally observed insulating ground states work in distinctly different ways for each compound.
Mot clés : Dioxydes d'actinides, Théorie $ \mathrm{LSDA}+\mathrm{U}$, Ordre multipolaire
@article{CRPHYS_2014__15_7_580_0,
author = {Nicola Magnani and Michi-To Suzuki and Peter M. Oppeneer},
title = {First-principles theory of multipolar order in actinide dioxides},
journal = {Comptes Rendus. Physique},
pages = {580--586},
publisher = {Elsevier},
volume = {15},
number = {7},
year = {2014},
doi = {10.1016/j.crhy.2014.07.003},
language = {en},
}
TY - JOUR AU - Nicola Magnani AU - Michi-To Suzuki AU - Peter M. Oppeneer TI - First-principles theory of multipolar order in actinide dioxides JO - Comptes Rendus. Physique PY - 2014 SP - 580 EP - 586 VL - 15 IS - 7 PB - Elsevier DO - 10.1016/j.crhy.2014.07.003 LA - en ID - CRPHYS_2014__15_7_580_0 ER -
Nicola Magnani; Michi-To Suzuki; Peter M. Oppeneer. First-principles theory of multipolar order in actinide dioxides. Comptes Rendus. Physique, Volume 15 (2014) no. 7, pp. 580-586. doi : 10.1016/j.crhy.2014.07.003. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2014.07.003/
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