Single-Crystal Diffuse Neutron Scattering Study of the Dipole-Octupole Quantum Spin-Ice Candidate Ce2Zr2O7 : No Apparent Octupolar Correlations Above T=0.05 K

The insulating magnetic pyrochlore Ce2Zr2O7 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 Ce2Zr2O7 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, Ce2Sn2O7 and Ce2Hf2O7, 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 Ce2Zr2O7. 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 Ce2Zr2O7, Ce2Sn2O7, and Ce2Hf2O7. 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 Ce2Zr2O7 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 Ce2Sn2O7 and Ce2Hf2O7, and to low-energy inelastic neutron scattering from single-crystal Ce2Zr2O7. Published by the American Physical Society 2025