Contrasting 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 Ba$_{0.5}$K$_{0.5}$Fe$_{2}$As$_{2}$ samples. It is found that the Mn-doping can depress the superconducting transition temperature drastically with a rate of $ΔT_c$/Mn-1% = -4.2 K, while that by Zn-doping is negligible. Detailed analysis reveals that the Mn-doping enhances the residual resistivity ($ρ_0$) significantly, and induces strong local magnetic moments ($\sim$ 2.58 $μ_B$) which play as pair breakers. While the impurity scattering measured by $ρ_0$ 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 affect the superconducting transition temperature weakly.

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