Open AccessThe fifty years it has taken to understand the dynamics of UO2 in its ordered state
Author(s) -
G. H. Lander,
R. Caciuffo
Publication year - 2020
Publication title -
journal of physics. condensed matter
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 228
eISSN - 1361-648X
pISSN - 0953-8984
DOI - 10.1088/1361-648x/ab1dc5
Subject(s) - magnon , antiferromagnetism , phonon , condensed matter physics , inelastic neutron scattering , anisotropy , excitation , physics , spin wave , coupling (piping) , neutron scattering , neutron , atomic physics , nuclear physics , materials science , ferromagnetism , quantum mechanics , metallurgy
In 1966 Roger Cowley (together with Gerald Dolling) reported the first neutron inelastic scattering from the magnetic excitations from UO 2 below its antiferromagnetic 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 UO 2 , but showed a keen interest in the developments. Forty years after this pioneering work, unambiguous evidence was found (using resonance x-ray techniques) for the ordering below T N of the electric quadrupoles involving the anisotropy of the 5 f 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.