Title: The fifty years it has taken to understand the dynamics of UO2 in its ordered state
Authors: LANDER G. H.CACIUFFO ROBERTO
Citation: JOURNAL OF PHYSICS-CONDENSED MATTER vol. 32 no. 37 p. 374001
Publisher: IOP PUBLISHING LTD
Publication Year: 2020
JRC N°: JRC115889
ISSN: 0953-8984 (online)
URI: https://publications.jrc.ec.europa.eu/repository/handle/JRC115889
DOI: 10.1088/1361-648X/ab1dc5
Type: Articles in periodicals and books
Abstract: In 1966 Roger Cowley (together with Gerald Dolling) reported the first neutron inelastic scattering from the magnetic excitations from UO2 below its antiferro-magnetic ordering temperature of 30 K. They showed the strong magnon-phonon coupling in this material and that the excitations appeared to contain an additional mode that was not anticipated. Cowley never returned to UO2, but showed a keen interest in the developments. 40 years after this pioneering work, unambiguous evidence was found (using resonance X-ray techniques) for the ordering below TN of the electric quadrupoles involving the anisotropy of the 5f charge distribution around the uranium nuclei. A further 10 years later, now armed with a full theory for the excitation spectrum expected for phonons, magnons, and quadrupoles, we can identify the latter as the source of the “extra” mode reported first in 1966. The story is a long winding one, with the expected serendipity and dead ends, but is now (almost) completed.
JRC Directorate:Nuclear Safety and Security

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