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arXiv · 2506.09911

Microscopic investigation of enhanced Pauli paramagnetism in metallic Pu$_2$C$_3$

R. Yamamoto·M. S. Cook·A. R. Altenhof·P. Sherpa·S. Park·J. D. Thompson·H. E. Mason·D. C. Arellano·D. V. Prada·P. H. Tobash·F. Ronning·E. D. Bauer·N. Harrison·W. A. Phelan·A. P. Dioguardi·M. Hirata
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Abstract

A combined study of the structural and electronic properties of polycrystalline Pu$_2$C$_3$ is reported based on x-ray diffraction, specific heat, magnetic susceptibility, ${}^{13}$C nuclear magnetic resonance (NMR), and band structure calculations. X-ray diffraction reveals a global noncentrosymmetric cubic lattice, with a nearest-neighbor C--C bond length of $r = 1.38$ \r{A}. ${}^{13}$C NMR measurements indicate that the global cubic symmetry is locally broken, revealing two unique carbon environments. Magnetic susceptibility suggests enhanced Pauli paramagnetism, and specific heat reveals a moderately large electronic Sommerfeld coefficient $\gamma = 45$ mJ mol$_{\mathrm{Pu}}^{-1}$ K$^{-2}$, with a Wilson ratio $R_W \approx 1.3$ further indicating moderate correlations. ${}^{13}$C nuclear spin-lattice relaxation rate ($1/T_1$) and Knight shift ($K$) measurements find metallic Korringa behavior (i.e., $T_1TK^2=$ const.) with modest ferromagnetic spin fluctuations at low temperature. Taken together, the data point to a delocalized nature of a narrow 5$f$-electron band with weak electronic correlations. Density functional theory band-structure calculations confirm the appearance of such narrow 5$f$ bands near the Fermi level. Our data provide prime evidence for a plutonium-based metallic system with weak electronic correlations, which sheds new light on the understanding of complex paramagnetism in actinide-based metallic compounds.

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R. Yamamoto, M. S. Cook, A. R. Altenhof, P. Sherpa, S. Park, J. D. Thompson, H. E. Mason, D. C. Arellano, D. V. Prada, P. H. Tobash, F. Ronning, E. D. Bauer, N. Harrison, W. A. Phelan, A. P. Dioguardi, M. Hirata. 2025-06-11. Microscopic investigation of enhanced Pauli paramagnetism in metallic Pu$_2$C$_3$. https://doi.org/10.1103/n911-574l

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