Unusual spin dynamics in the low-temperature magnetically ordered state of Ag$_{3}$LiIr$_{2}$O$_{6}$

Abstract

Recently, there have been contrary claims of Kitaev spin-liquid behaviour and ordered behavior in the honeycomb compound Ag3LiIr2O6 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 (µSR) time spectrum below 9 K till 52 mK. Coincidentally in 7 Li nuclear magnetic resonance, a wipe-out of the signal is observed below ∼ 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 Li shift and spin-lattice relaxation rate also show anomalies at ∼ 50 K. They are likely related to the onset of dynamic magnetic correlations, but their origin is not completely clear. Detailed analysis of our µSR data is consistent with a co-existence of incommensurate Néel and striped environments. A significant and undiminished dynamical relaxation rate (∼ 5 MHz) as seen in µSR deep into the ordered phase indicates enhanced quantum fluctuations in the ordered state.

Kitaev Magnetism through the Prism of Lithium Iridate

“…The problem of stacking disorder appears most prominently in Ag 3 LiIr 2 O 6 that has been prepared with different amounts of stacking faults. Samples with a low concentration of stacking faults show long-range magnetic order, [119,126,127] whereas samples with a high concentration of stacking faults develop a disordered magnetic state resembling a spin liquid. [93] This observation is in line with the previous work on pure α-Li 2 IrO 3 where magnetic ordering transition is also suppressed when the concentration of stacking faults increases.…”