Recently, there have been contrary claims of Kitaev spin-liquid behavior and ordered behavior in the honeycomb compound ${\mathrm{Ag}}_3\mathrm{Li}{\mathrm{Ir}}_2{\mathrm{O}}_6$ based on various experimental signatures. Our investigations on this system reveal a low-temperature ordered state with persistent dynamics down to the lowest temperatures. Magnetic order is confirmed by clear oscillations in the muon spin relaxation ($\mu \mathrm{SR}$) time spectrum below 9 K until 52 mK. Coincidentally in ${}^7\mathrm{Li}$ nuclear magnetic resonance, a wipeout of the signal is observed below $\sim 10$ K, which again strongly indicates magnetic order in the low-temperature regime. This is supported by our density functional theory calculations which show an appreciable Heisenberg exchange term in the spin Hamiltonian that favors magnetic ordering. The ${}^7\mathrm{Li}$ shift and spin-lattice relaxation rate also show anomalies at $\sim 50$ K. They are likely related to the onset of dynamic magnetic correlations, but their origin is not completely clear. Detailed analysis of our $\mu \mathrm{SR}$ data is consistent with a coexistence of incommensurate Néel and striped environments. A significant and undiminished dynamical relaxation rate ($\sim 5$ MHz) as seen in $\mu \mathrm{SR}$ deep into the ordered phase indicates enhanced quantum fluctuations in the ordered state.

• Received 2 May 2021
• Revised 6 August 2021
• Accepted 10 August 2021

DOI:https://doi.org/10.1103/PhysRevB.104.115106