Structure and anisotropic properties of BaFe2-x Nix As2 (x=0, 1, and 2) single crystals

The crystal structure, electrical resistivity, magnetic susceptibility, and heat capacity of single crystals of BaFe2 As2, BaNi2 As2, and BaFeNiAs2 are reported. BaFe2 As2 data indicate the equivalence of C (T), d (χT) /dT, and dρ/dT results in determining the antiferromagnetic transition at TN =132 (1) K. BaNi2 As2 shows a structural phase transition from a high-temperature tetragonal phase to a low-temperature triclinic phase (P 1̄ symmetry) at T0 =131 K, with superconducting critical temperature Tc =0.69 K. BaFeNiAs2 does not show any sign of superconductivity and its properties resemble BaCo2 As2, a renormalized paramagnetic metal.