We investigate the temperature dependence of the spin dynamics in the pyrochlore magnet ${\mathrm{Nd}}_2{\mathrm{Zr}}_2{\mathrm{O}}_7$ by neutron scattering experiments. At low temperature, this material undergoes a transition towards an “all-in–all-out” antiferromagnetic phase and the spin dynamics encompass a dispersionless mode, characterized by a dynamical spin ice structure factor. Unexpectedly, this mode is found to survive above $T_N\approx 300\mathrm{mK}$. Concomitantly, elastic correlations of the spin ice type develop. These are the signatures of a peculiar correlated paramagnetic phase which can be considered as a new example of Coulomb phase. Our observations near $T_N$ do not reproduce the signatures expected for a Higgs transition, but show reminiscent features of the “all-in–all-out” order superimposed on a Coulomb phase.

• Received 26 November 2020
• Revised 15 April 2021
• Accepted 17 May 2021

DOI:https://doi.org/10.1103/PhysRevLett.126.247201