Single-crystal growth of Ba_1-xK_xFe₂As₂ by KAs self-flux method

Single crystals of Ba_1-xK_xFe₂As₂ with 0.15 = x = 1 have been successfully synthesized by a KAs self-flux method. The potassium (K) concentration x of the grown crystals was systematically changed by changing the mixing ratio of Ba to Fe in the starting materials. The crystals have flat surfaces corresponding to the crystallographic (001) planes, whose planar dimensions increase with decreasing thickness when x increases. The superconducting transition temperature systematically changes with x, ranging from 38K at x = 0.4 to 3.4K at x = 1.0, in good agreement with the results for polycrystalline samples.