Structure and anisotropic properties of BaFe2−xNixAs2 (x=0, 1, and 2) single crystals

The crystal structure, electrical resistivity, magnetic susceptibility, and heat capacity of single crystals of BaFe2As2, BaNi2As2, and BaFeNiAs2 are reported. BaFe2As2 data indicate the equivalence of C T , d T /dT, and d /dT results in determining the antiferromagnetic transition at TN=132 1 K. BaNi2As2 shows a structural phase transition from a high-temperature tetragonal phase to a low-temperature triclinic phase P1̄ 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 BaCo2As2, a renormalized paramagnetic metal.