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Description
Coulomb phases can be constructed for degrees of freedom that obey an ice rule on the pyrochlore lattice. Using diffuse and single crystal neutron and powder x-ray scattering, we identify a structural Coulomb phase (charge ice) formed by the Ni$^{2+}$ and Cr$^{3+}$ cations in CsNiCrF$_6$. The cations form a configurational structural ice and dictate local distortions of the (Ni/Cr)F$_6$ octahedra, which inherit Coulomb phase correlations. The resulting exchange disorder can be mapped to a fully-packed loop model. Despite this disorder, diffuse and inelastic magnetic neutron scattering show that the spins also form a Coulomb phase, whose correlations and dynamics have much in common with those of the canonical pyrochlore Heisenberg antiferromagnet.
T. Fennell et al., Nat. Phys. 19, 60 (2019)
