Single-Crystal Diffuse Neutron Scattering Study of the Dipole-Octupole Quantum Spin-Ice Candidate Ce_2⁢Zr₂⁢O₇: No Apparent Octupolar Correlations Above 𝑇 = 0.05 K

Journal Article · Tue Apr 29 00:00:00 EDT 2025 · Physical Review. X

DOI:https://doi.org/10.1103/PhysRevX.15.021033· OSTI ID:2563486

Smith, E. M. ^[1]; Schäfer, R. ^[2]; Dudemaine, J. ^[3]; Placke, B. ^[4]; Yuan, B. ^[1]; Morgan, Zachary ^[5]; Ye, F. ^[5]; Moessner, Roderich ^[6]; Benton, Owen ^[7]; Bianchi, A. D. ^[3]; Gaulin, B. D. ^[8]

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1. McMaster Univ., Hamilton, ON (Canada)
2. Boston Univ., MA (United States)
3. Univ. of Montreal, QC (Canada); Regroupement Québécois sur les Matériaux de Pointe (RQMP), Montreal, QC (Canada)
4. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems; Univ. of Oxford (United Kingdom)
5. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
6. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems
7. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems; Queen Mary Univ. of London (United Kingdom)
8. McMaster Univ., Hamilton, ON (Canada); Canadian Institute for Advanced Research (CIFAR), Toronto, ON (Canada)

The insulating magnetic pyrochlore Ce₂⁢Zr₂⁢O₇ has gained attention as a quantum spin-ice candidate with dipole-octupole character that arises from the crystal-electric-field ground-state doublet for the Ce³⁺ Kramers ion. This dipole-octupole character permits both spin-ice phases based on magnetic dipoles and those based on more-exotic octupoles. This work reports low-temperature neutron diffraction measurements on single-crystal Ce₂⁢Zr_2⁢O₇ with 𝑄 coverage both at low 𝑄, where the magnetic form factor for dipoles is near maximal, and at high 𝑄, covering the region where the magnetic form factor for Ce³⁺ octupoles is near maximal. This study was motivated by recent powder neutron diffraction studies of other Ce-based dipole-octupole pyrochlores, Ce₂⁢Sn₂⁢O₇ and Ce₂⁢Hf₂⁢O₇, which each showed temperature-dependent diffuse diffraction at high 𝑄, interpreted as arising from octupolar correlations. Our measurements use an optimized single-crystal diffuse scattering instrument that allows us to screen against strong Bragg scattering from Ce₂⁢Zr₂⁢O₇. The temperature-difference neutron diffraction reveals a low-𝑄 peak consistent with dipolar spin-ice correlations reported in previous work, and an alternation between positive and negative net intensity at higher 𝑄. These features are consistent with our numerical-linked-cluster calculations using pseudospin interaction parameters previously reported for Ce₂⁢Zr_2⁢O₇, Ce₂⁢Sn₂⁢O₇, and Ce₂⁢Hf₂⁢O₇. Importantly, neither the measured data nor any of the NLC calculations show evidence for increased scattering at high 𝑄 resulting from octupolar correlations. We conclude that at the lowest attainable temperature for our measurements (𝑇 = 0.05 K), scattering from octupolar correlations in Ce₂⁢Zr₂⁢O₇ is not present in the neutron diffraction signal on the level of our observation threshold of around 0.1% of the low-𝑄 dipole scattering. We compare these results to those obtained earlier on powder Ce₂⁢Sn₂⁢O₇ and Ce_2⁢Hf_2⁢O₇, and to low-energy inelastic neutron scattering from single-crystal Ce₂⁢Zr₂⁢O₇.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: Natural Sciences and Engineering Research Council of Canada (NSERC); US Air Force Office of Scientific Research (AFOSR); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 2563486
• Alternate ID(s): OSTI ID: 2573181
• Journal Information: Physical Review. X, Journal Name: Physical Review. X Journal Issue: 2 Vol. 15; ISSN 2160-3308
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE