1. Single Crystal Diffuse Neutron Scattering Study of the Dipole-Octupole Quantum Spin Ice Candidate Ce$_2$Zr$_2$O$_7$: No Apparent Octupolar Correlations Above $T = 0.05$ K
- Author
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Smith, E. M., Schäfer, R., Dudemaine, J., Placke, B., Yuan, B., Morgan, Z., Ye, F., Moessner, R., Benton, O., Bianchi, A. D., and Gaulin, B. D.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
The insulating magnetic pyrochlore Ce$_2$Zr$_2$O$_7$ has attracted much attention as a quantum spin ice candidate with dipole-octupole character that permits spin ice phases based not only on magnetic dipole moments but also allows for even-more-exotic octupole-based spin ice phases. This work reports low-temperature neutron diffraction measurements on single crystal Ce$_2$Zr$_2$O$_7$ 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 Ce$^{3+}$ octupoles is near maximal. This study was motivated by recent powder neutron diffraction studies of other Ce-based dipole-octupole pyrochlores, Ce$_2$Sn$_2$O$_7$ and Ce$_2$Hf$_2$O$_7$, which each showed temperature-dependent diffuse diffraction at high $Q$ that was interpreted as arising from octupolar correlations. Our measurements use an optimized single crystal diffuse scattering instrument that allows us to screen against strong single crystal Bragg scattering in Ce$_2$Zr$_2$O$_7$. The temperature-difference neutron diffraction reveals a low-$Q$ peak consistent with dipolar spin ice correlations. For larger $Q$, the temperature-difference neutron diffraction shows an alternation between positive and negative net intensity. These features are qualitatively consistent with the corresponding numerical-linked-cluster (NLC) calculations using pseudospin interaction parameters reported for Ce$_2$Zr$_2$O$_7$, Ce$_2$Sn$_2$O$_7$, or Ce$_2$Hf$_2$O$_7$. Importantly, neither the measured data nor any of the NLC calculations show increased scattering at high $Q$ resulting from octupolar correlations. We conclude that at the lowest attainable temperatures for our measurement ($T = 0.05$ K), octupolar correlations are not present in Ce$_2$Zr$_2$O$_7$ on the level of our observation threshold of $\sim$ 0.1$\%$ of the low-$Q$ dipole scattering.
- Published
- 2024