# Unconventional magnetism in the 4d$^{4}$ based ($S=1$) honeycomb system Ag$_{3}$LiRu$_{2}$O$_{6}$

## TL;DR

This study explores the unconventional magnetic behavior of Ag$_{3}$LiRu$_{2}$O$_{6}$, a 4d$^{4}$ honeycomb system, revealing dynamic, gapless spin correlations without long-range order and suggesting complex magnetic interactions.

## Contribution

It provides the first detailed investigation of magnetic properties and underlying interactions in Ag$_{3}$LiRu$_{2}$O$_{6}$, highlighting its potential for novel magnetism.

## Key findings

- No magnetic long-range order down to 0.4 K.
- Evidence of gapless spin excitations and dynamic correlations.
- Indications of spin freezing below 5 K with borderline static/dynamic magnetism.

## Abstract

We have investigated the thermodynamic and local magnetic properties of the Mott insulating system Ag$_{3}$LiRu$_{2}$O$_{6}$ containing Ru$^{4+}$ (4$d$$^{4}$) for novel magnetism. The material crystallizes in a monoclinic $C2/m$ structure with RuO$_{6}$ octahedra forming an edge-shared two-dimensional honeycomb lattice with limited stacking order along the $c$-direction. The large negative Curie-Weiss temperature ($\theta_{CW}$ = -57 K) suggests antiferromagnetic interactions among Ru$^{4+}$ ions though magnetic susceptibility and heat capacity show no indication of magnetic long-range order down to 1.8 K and 0.4 K, respectively. $^{7}$Li nuclear magnetic resonance (NMR) shift follows the bulk susceptibility between 120-300 K and levels off below 120 K. Together with a power-law behavior in the temperature dependent spin-lattice relaxation rate between 0.2 and 2 K, it suggest dynamic spin correlations with gapless excitations. Electronic structure calculations suggest an $S = 1$ description of the Ru-moments and the possible importance of further neighbour interactions as also bi-quadratic and ring-exchange terms in determining the magnetic properties. Analysis of our $\mu$SR data indicates spin freezing below 5 K but the spins remain on the borderline between static and dynamic magnetism even at 20 mK.