AgRuO3, a Strongly Exchange-Coupled Honeycomb Compound Lacking Long-Range Magnetic Order

Quasi two-dimensional (2D) oxide-based honeycomb lattices have attracted great attention for displaying specific electronic instabilities, which give rise to unconventional bonding patterns and unexpected magnetic exchange couplings. The synthesis of AgRuO3, another representative exhibiting unique structural properties, is reported here. The stacking sequence of the honeycomb layers (Ru2O6) differs from analogous precedents; in particular, the intercalating silver atoms are shifted from the middle of the interspaces and cap the void octahedral sites of the (Ru2O6) slabs from both sides. This way, charge neutral, giant 2D molecules of Ag/Ru2O6/Ag result; a feature that significantly enhances the overall 2D character of AgRuO3. Measurements of magnetization have revealed extremely strong magnetic exchange coupling to be present, surviving to a temperature as high as 673K, which is the temperature of thermal decomposition. No indication for long-range magnetic order has, however, been observed. Theoretical analyses confirm the pronounced 2D character of the electronic system, and in particular reveal the inter-honeycomb layer coupling J(c) to be distinctly weak.