[Le point sur les études des oxydes d'actinides par RMN]
Dans ce papier, nous passons brièvement en revue les propriétés de l'état fondamental des oxydes cubiques AnO2, avec , Np, Pu et Am, telles que révélées principalement par les études RMN du ligand 17O2−. Pour PuO2, où l'état fondamental dans le champ cristallin cubique est un singulet non magnétique, seul le 239Pu a été mesuré dans une étude récente, qui représente une percée pour ce qui concerne cet isotope d'accès difficile. UO2 a un état fondamental antiferromagnétique (AFM) exotique à quatre sous-réseaux, tandis que NpO2 montre le premier état fondamental multipolaire identifié dans un composé d'actinide, consistant en un mélange d'ordre octupolaire et de rang 5 (triakontadipolaire). Par ailleurs, AmO2, même avec son isotope possédant la plus longue période, 243Am, devient si rapidement désordonné du fait des dommages qu'il subit par auto-irradiation que son état fondamental était simplement, dans une étude récente, un verre de spins, alors que l'état fondamental réel du composé cubique cristallin demeure masqué par cette difficulté expérimentale. L'accent est mis sur la façon dont les mesures RMN sur le noyau 17O complètent les autres données expérimentales pour confirmer et vérifier l'état fondamental, souvent exotique, établi pour les systèmes AnO2.
In this paper, we offer a brief review of the ground-state properties of the cubic oxides AnO2, where , Np, Pu and Am, as revealed mainly by NMR studies of the 17O2− ligand. For PuO2, where the ground state is a nonmagnetic singlet eigenstate of the cubic crystal field, only the 239Pu has been studied, in a recent breakthrough observation of this elusive isotope [1]. For UO2 and NpO2, the former has an exotic four-sublattice antiferromagnetic (AFM) ground state, while the latter has the first multipolar ground state to be identified among actinide compounds, namely a mixture of octupolar and rank 5 (triakontadipolar) order. On the other hand AmO2, even with the longest-lived isotope 243Am, becomes disordered so quickly from radiation self-damage that its ground state in a recent study was simply a spin glass, while the actual ground state of the cubic crystalline compound remains obscured by this experimental problem. The emphasis throughout is on how 17O NMR studies complement other experimental data to confirm and verify the known exotic magnetic ground states of AnO2 systems.
Mot clés : Oxydes d'actinides, Ordre multipolaire, Résonance magnétique nucléaire
@article{CRPHYS_2014__15_7_563_0,
author = {Russell E. Walstedt and Yo Tokunaga and Shinsaku Kambe},
title = {NMR studies of actinide oxides {\textendash} {A} review},
journal = {Comptes Rendus. Physique},
pages = {563--572},
publisher = {Elsevier},
volume = {15},
number = {7},
year = {2014},
doi = {10.1016/j.crhy.2014.06.007},
language = {en},
}
Russell E. Walstedt; Yo Tokunaga; Shinsaku Kambe. NMR studies of actinide oxides – A review. Comptes Rendus. Physique, Volume 15 (2014) no. 7, pp. 563-572. doi : 10.1016/j.crhy.2014.06.007. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2014.06.007/
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