Effect of Zn doping on spin-density wave and superconductivity in LaFe$_{1-x}$Zn$_x$AsO and LaFe$_{1-x}$Zn$_x$AsO$_{0.9}$F$_{0.1}$

Abstract

We report Zn-doping effect in the parent and F-doped LaFeAsO oxy-arsenides. Slight Zn doping in LaFe$_{1-x}$Zn$_{x}$AsO drastically suppresses the resistivity anomaly around 150 K which is associated with formation of antiferromagnetic (AFM) spin density wave (SDW) in the undoped parent compound. Meanwhile Zn doping does not affect or even enhances the $T_c$ of LaFe$_{1-x}$Zn$_{x}$AsO$_{0.9}$F$_{0.1}$, in contrast to the effect of Zn doping in high-$T_c$ cuprates. This result clearly indicates that the non-magnetic impurities such as Zn$^{2+}$ ions in the Fe$_2$As$_2$ conducting layers affects selectively the AFM order, and superconductivity remains almost unperturbed or even enhanced.