Single crystal growth and characterizations of iron arsenide superconductor BaFe_2-xNi_xAs₂ (0.0 ≤ x ≤0.12)

A series of big single crystals of BaFeFe_2-xNi_xAs₂ have been prepared by the FeAs self-flux method, with nominal nickel doping x = 0--0.12. The dimensions of the cleaved crystals are over 10 mm along ab plane and ～2 mm in maximum along the c direction. The measurements of x-ray diffraction, electrical resistance and magnetic property are carried out on the crystals. For the undoped parent compound BaFe₂As₂, both resistance and magnetization data display an anomaly associated with spin density wave and/or structural phase transition, with the transition temperatures at ～138 K. For Ni-doped BaFe_2-xNi_xAs₂ crystals, the superconducting critical temperature T_c ranges from 4.3 K for x = 0.06 sample to 20 K for the optimally doped x = 0.10 crystal.