Anisotropy in BaFe ₂Se ₃ single crystals with double chains of FeSe tetrahedra

We studied the anisotropy in physical properties of Ba _1.00(4)Fe _1.9(1)Se _3.1(1) single crystals. BaFe ₂Se ₃ is a semiconductor below 300 K. Magnetization measurements show that there is a crossover from short-range antiferromagnetic (AFM) correlations at room temperature to a long-range AFM order with T _N=255 K. The anisotropy of magnetization is consistent with the previous neutron results. This crossover is supported by the heat-capacity measurement, where the phase-transition peak is absent at 255 K. The superconducting transition at about 10 K is likely due to the small amount of β-FeSe impurities.