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Probing the Pu4+ magnetic moment in PuF4 with F19 NMR spectroscopy

Cigdem Capan, Richard J. Dempsey, Sergey Sinkov, Bruce K. McNamara, and Herman Cho
Phys. Rev. B 93, 224409 – Published 8 June 2016
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  • INTRODUCTION
  • EXPERIMENTAL
  • RESULTS AND DISCUSSION
  • CONCLUSION
  • ACKNOWLEDGMENTS
    • References

    Abstract

    The magnetic fields produced by Pu4+ centers have been measured by F19 NMR spectroscopy to elucidate the Pu-F electronic interactions in polycrystalline PuF4. Spectra acquired at applied fields of 2.35 and 7.05 T reveal a linear scaling of the F19 line shape. A model is presented that treats the line broadening and shifts as due to dipolar fields produced by Pu valence electrons in localized noninteracting orbitals. Alternative explanations for the observed line shape involving covalent Pu-F bonding, superexchange interactions, and electronic configurations with enhanced magnetic moments are considered.

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    • Received 15 April 2016
    • Revised 18 May 2016

    DOI:https://doi.org/10.1103/PhysRevB.93.224409

    ©2016 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Chemical bondingElectronic structure of atoms & moleculesParamagnetism
    1. Techniques
    Nuclear magnetic resonance
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    Cigdem Capan1, Richard J. Dempsey1, Sergey Sinkov2, Bruce K. McNamara2, and Herman Cho3,*

    • 1Washington State University, Richland, Washington 99352, USA
    • 2Energy and Environmental Directorate, P.O. Box 999, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
    • 3Physical and Computational Sciences Directorate, P.O. Box 999, Pacific Northwest National Laboratory, Richland, Washington 99352, USA

    • *hm.cho@pnnl.gov

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    Vol. 93, Iss. 22 — 1 June 2016

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    Images

    • Figure 1
      Figure 1

      Monoclinic crystal structure of PuF4 illustrating the coordination of Pu (blue) with eight fluorine atoms (green) and the near linearity of the Pu-F-Pu bridges.

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    • Figure 2
      Figure 2

      Integrated F19 NMR signal intensities vs delay time for PuF4 measured at 2.35 T. Measurements at the two indicated frequencies in the inhomogeneously broadened line shape are shown, along with fits to a single-exponential recovery function.

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    • Figure 3
      Figure 3

      Fluorine-19 spectra of PuF4(s). Experimental spectral intensities were measured as a function of the spectrometer carrier frequency at magnetic fields of 7.05 T (a) and 2.35 T (b), and are indicated by red crosses. Solid curves in (a) and (b) are fits of the function in Eq. (2) to the experimental data; nonfitted features centered at ∼0 ppm are from residual F19 background signal. Simulated spectra were computed with models that assume 5f4 (c) and 5f3 6d1 (d) Pu electronic configurations (vide infra); these spectra have been centered at the same isotropic shift frequency as (a) and (b) (δ0=−1620 ppm) symbolized by the dashed line. Note that at fixed field, energy increases from right to left on the δ scale.

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