Magnetic and electronic ordering phenomena in the [Ru$_2$O$_6$] honeycomb lattice compound AgRuO$_3$

Abstract

The silver ruthenium oxide AgRuO3 consists of honeycomb [Ru 5+ 2 O 2− 6 ] layers, and can be considered an analogue of SrRu2O6 with a different intercalation stage. We present measurements of magnetic susceptibility and specific heat on AgRuO3 single crystals which reveal a sharp antiferromagnetic transition at 342(3) K. The electrical transport in single crystals of AgRuO3 is determined by a combination of activated conduction over an intrinsic semiconducting gap of ≈ 100 meV and carriers trapped and thermally released from defects. From powder neutron diffraction data a Néeltype antiferromagnetic structure with the Ru moments along the c axis is derived. Raman and muon spin rotation spectroscopy measurements on AgRuO3 powder samples indicate a further weak phase transition or a crossover in the temperature range 125-200 K. The transition does not show up in magnetic susceptibility and its origin is argued to be related to defects but cannot be fully clarified. The experimental findings are complemented by DFT-based electronic structure calculations. It is found that the magnetism in AgRuO3 is similar to that of SrRu2O6, however with stronger intralayer and weaker interlayer magnetic exchange interactions.