Superconductivity suppression of Ba0.5K0.5Fe2-2xM2xAs2 single crystals   by substitution of transition-metal (M = Mn, Ru, Co, Ni, Cu, and Zn)
  We investigated the doping effects of magnetic and nonmagnetic impurities on the single-crystalline p-type Ba0.5K0.5Fe2-2xM2xAs2 (M = Mn, Ru, Co, Ni, Cu and Zn) superconductors. The superconductivity indicates robustly against impurity of Ru, while weakly against the impurities of Mn, Co, Ni, Cu, and Zn. However, the present Tc suppression rate of both magnetic and nonmagnetic impurities remains much lower than what was expected for the s\pm-wave model. The temperature dependence of resistivity data is observed an obvious low-T upturn for the crystals doped with high-level impurity, which is due to the occurrence of localization. Thus, the relatively weak Tc suppression effect from Mn, Co, Ni, Cu, and Zn are considered as a result of localization rather than pair-breaking effect in s\pm-wave model. 
Jun Li, Yanfeng Guo, Shoubao Zhang, Jie Yuan, Yoshihiro Tsujimoto, Xia   Wang, C. I. Sathish, Ying Sun, Shan Yu, Wei Yi, Kaz...
cond-mat.supr-con