Doping effect of Cu and Ni impurities on the Fe-based superconductor Ba0.6K0.4Fe2As2Peng Cheng, Bing Shen, Fei Han and Hai-Hu WenEPL, 104 3 (2013) 37007DOI: https://doi.org/10.1209/0295-5075/104/37007