Ba$_{2}$CoO$_{4}$: Crystal Growth, Structure Refinement, and Physical Properties

Single crystalline Ba$_{2}$CoO$_{4}$ is grown for the first time using the floating-zone technique. Single-crystal refinement of X-ray diffraction data indicates that Ba$_{2}$CoO$_{4}$ has a monoclinic structure with $a$ = 5.9176(13) {\AA}, $b$ = 7.6192(16) {\AA}, $c$ = 10.3790(22) {\AA}, and {\ss} = 91.734(4)$^{o}$ at room temperature. Magnetic susceptibility, specific heat, and thermal conductivity show anomalies at T$_{N}$ = 25 K, due to antiferromagnetic ordering. However, the magnitude of the N\'{e}el temperature T$_{N}$ is significantly lower than the Curie-Weiss temperature ($\vert \Theta \vert \sim $ 110 K), suggesting either reduced-dimensional magnetic interactions and/or the existence of magnetic frustration. The latter may be induced by disorder evident from the variable-range-hopping behavior in electrical resistivity, non-zero T term in specific heat and T$^{2}$ dependence in thermal conductivity at low temperatures.