Effect of Zn doping on magnetic order and superconductivity in LaFeAsO

Mi He,Yuke Li,Qian Tao,Xiao Lin,Guanghan Cao,Zhu'An Xu,Linjun Li,Cao Wang,Tong Zhou,Qingbo Wang

doi:10.1088/1367-2630/11/5/053008

Abstract

We report Zn-doping effect in the parent and F-doped LaFeAsO oxy-arsenides. Slight Zn doping in LaFe1- xZnxAsO drastically suppresses the resistivity anomaly around 150 K associated with the antiferromagnetic (AFM) spin density wave (SDW) in the parent compound. The measurements of magnetic susceptibility and thermopower confirm further the effect of Zn doping on AFM order. Meanwhile Zn doping does not affect or even enhances the Tc of LaFe1-xZnxAsO0.9F0.1, in contrast to the effect of Zn doping in high-Tc cuprates. We found that the solubility of Zn content (x) is limited to less than 0.1 in both systems and further Zn doping (i.e. x ⩾0.1) causes phase separation. Our study clearly indicates that the non-magnetic impurity of Zn2+ ions doped in the Fe2As2 layers affects selectively the AFM order and superconductivity remains robust against the Zn doping in the F-doped superconductors.

Highlights

Powder x-ray diffraction (XRD) was performed at room temperature using a D/Max-rA diffractometer with Cu Kα radiation and a graphite monochromator
For the parent compound and slightly Zn-doped compounds (x 0.05), the XRD peaks can be well indexed based on a tetragonal cell with the space group of P4/nmm, which indicates that the samples are essentially single phase
Whereas the anomaly in the resistivity is completely suppressed in the parent compound, the superconductivity in the F-doped system remains almost unperturbed by Zn doping, which reveals that doped Zn2+ ions affect selectively AFM order and the disorder caused by Zn doping has little effect on the superconducting electron pairing

Summary

Introduction

Powder x-ray diffraction (XRD) was performed at room temperature using a D/Max-rA diffractometer with Cu Kα radiation and a graphite monochromator. For x 0.10, there is a large increase in the resistivity, consistent with the fact that the LaFe1−x Znx AsO samples become phase separated for x 0.10 as shown by the XRD patterns.

Results

Conclusion