Contrasting impurity scattering and pair-breaking effects by doping Mn and Zn in Ba0.5K0.5Fe2As2

Resistivity, Hall effect, magnetoresistance and dc magnetization were measured in Mn- and Zn-doped Ba0.5K0.5Fe2As2 samples. It is found that the Mn doping can depress the superconducting transition temperature drastically with a rate of Delta T-c/Mn-1%=-4.2 K, while that by Zn doping is negligible. Detailed analysis reveals that the Mn doping enhances the residual resistivity (rho(0)) significantly, and induces strong local magnetic moments (similar to 2.58 mu(B)) which play as pair breakers. While the impurity scattering measured by rho(0) in the Zn-doped samples is much weaker, accompanied by a negligible pair-breaking effect. A possible explanation is that the impurity scattering by the Zn impurities are mainly small angle scattering (or small momentum transfer), therefore it cannot break the pairing induced by the interpocket scattering and thus affects the superconducting transition temperature weakly.