We have investigated the thermodynamic and local magnetic properties of the Mott insulating system Ag3LiRu2O6 containing Ru4+ (4d4) for novel magnetism. The material crystallizes in a monoclinic C2/m structure with RuO6 octahedra forming an edge-shared two-dimensional honeycomb lattice with limited stacking order along the c-direction. The large negative Curie-Weiss temperature (θCW = -57 K) suggests antiferromagnetic interactions among Ru4+ 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. 7Li 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 μSR data indicates spin freezing below 5 K but the spins remain on the borderline between static and dynamic magnetism even at 20 mK.
@article{arxiv.1902.01653,
title = {Unconventional magnetism in the 4d$^{4}$ based ($S=1$) honeycomb system Ag$_{3}$LiRu$_{2}$O$_{6}$},
author = {R. Kumar and Tusharkanti Dey and P. M. Ette and K. Ramesha and Atasi Chakraborty and I. Dasgupta and J. C. Orain and C. Baines and Sándor Tóth and A. Shahee and S. Kundu and M. Prinz-Zwick and A. A. Gippius and N. Büttgen and P. Gegenwart and A. V. Mahajan},
journal= {arXiv preprint arXiv:1902.01653},
year = {2019}
}