The effect of Cr impurity to superconductivity in electron-doped   BaFe2-xNixAs2
  We use transport and magnetization measurements to study the effect of Cr-doping to the phase diagram of the electron-doped superconducting BaFe2-xNixAs2 iron pnictides. In principle, adding Cr to electron-doped BaFe2-xNixAs2 should be equivalent to the effect of hole-doping. However, we find that Cr doping suppresses superconductivity via impurity effect, while not affecting the normal state resistivity above 100 K. We establish the phase diagram of Cr-doped BaFe2-x-yNixCryAs2 iron pnictides, and demonstrate that Cr-doping near optimal superconductivity restore the long-range antiferromagnetic order suppressed by superconductivity. 
Rui Zhang, Dongliang Gong, Xingye Lu, Shiliang Li, Pengcheng Dai and   Huiqian Luo
cond-mat.supr-con cond-mat.str-el