Abstract
Vibrational and magnetic properties of single-crystal uranium-thorium dioxide (UxTh1−xO2) with a full range of 0<x<1 are investigated. Thorium dioxide is a diamagnet whose thermal properties are governed by lattice vibration. The addition of paramagnetic uranium ions leads to the emergence of magnetic effects that alter the thermophysical properties noticeably even at room temperature. The interaction of phonons with magnetic moments of uranium 5f electrons mediated by magnetoelastic coupling results in an anomalous low-temperature thermal conductivity profile. Analysis of the magnetic susceptibility measurements indicates a departure from the Curie-Weiss relationship characteristic of noninteracting paramagnetic ions, previously associated with the dynamic Jahn-Teller (DJT) effect characterized by coupling between spin and the oxygen sublattice. The T2g Raman peak position follows a nonlinear trend as a function of uranium concentration and hints that these Raman active optical modes play a role in either DJT or in mediating quadrupole-quadrupole interactions. A first-principle-based thermal transport model is implemented to explain the low-temperature transport measurements, where the anomalous reduction is attributed to phonon-spin resonant scattering. The interplay between spins and phonons is also captured using high-resolution inelastic x-ray scattering (IXS) measurements of phonon linewidths. Our results provide insights into the phonon interactions with the magnetic excitations governing DJT effect and impacting the low-temperature thermal transport processes in this material system. These findings have implications for understanding low-temperature thermal transport and magnetic properties in advanced materials for information processing and energy applications.
| Original language | English |
|---|---|
| Article number | 084404 |
| Journal | Physical Review Materials |
| Volume | 9 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 8 2025 |
Funding
This work was supported by Center for Thermal Energy Transport under Irradiation (TETI), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences. S.A. and M.K. would like to acknowledge The Ohio Supercomputer Center for providing High Performance Computing resources. S.Z. would like to acknowledge the High Performance Computing Center at Idaho National Laboratory, which are supported by the DOE Office of Nuclear Energy and the Nuclear Science User Facilities under Contract No. DE-AC07-05ID14517. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.Z.H., J.M.M., D.H.H., M.E.E., and M.K. conceptualized the work; K.R., T.P., and J.M.M. fabricated the samples; S.A., Z.H., H.M., S.R., and K.R. conducted the experiments; S.A., Z.H., P.U., and E.N. analyzed experimental results; S.Z. performed DFT calculations; S.A. performed phonon calculations; S.A. and M.K. performed integrated analysis; S.A. and M.K. drafted manuscript with all authors providing input, reviewing, and editing; J.M.M., K.G., D.H.H., M.E.E., and M.K. provided resources and supervision; D.H.H. and M.K. project administration; and D.H.H. funding acquisition. This work was supported by Center for Thermal Energy Transport under Irradiation (TETI), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences. S.A. and M.K. would like to acknowledge The Ohio Supercomputer Center for providing High Performance Computing resources. S.Z. would like to acknowledge the High Performance Computing Center at Idaho National Laboratory, which are supported by the DOE Office of Nuclear Energy and the Nuclear Science User Facilities under Contract No. DE-AC07-05ID14517. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.