Absence of Magnetic Order in Ising Honeycomb-Lattice Ba₃Co₂O₆(CO₃)_0.7

Ba₃Co₂O₆(CO₃)_0.7 is a rare example of Ising spin chains on a honeycomb lattice. We have found the quasi-one-dimensional electric conduction and its localization at low temperatures below 100 K The magnetic susceptibility exhibits the highly anisotropic Curie-Weiss behavior with the Weiss constant of 69 K for the magnetic field parallel to the chain and −104 K for perpendicular to the chain, which indicates the intrachain ferromagnetic interaction and the interchain antiferromagnetic one. No indication of magnetic order was observed down to 2 K Based on these experimental results, we suggest the spin liquid state.