Effect of Zn doping in hole-type 1111 phase (Pr, Sr)FeAsO.

There is an anomalous broad hump in the normal state resistivity in hole-type 1111 phase FeAs-based superconductors and its origin is an open issue. We study the effect of Zn doping on this anomaly in order to determine whether it is associated with the residual structural/antiferromagnetic (AFM) phase transition as in the parent compounds. A series of Zn doped Pr₀.₈Sr₀.₂FeAsO samples are prepared and their resistivity, magnetoresistance, Hall effect and specific heat are measured. Zn doping should not introduce extra charge carriers, and instead it can suppress the structural/AFM transition efficiently in the parent LaFeAsO system. The hump in resistivity remains unchanged with 6% Zn doping in Pr₀.₈Sr₀.₂FeAsO. The measurements of magnetoresistance reveal that the magnetoresistance is negligible in the Zn doped Pr₀.₈Sr₀.₂FeAsO samples, in contrast to the large positive magnetoresistance below the temperature of structure/AFM phase transition in the parent compound PrFeAsO. The results indicate that the anomalous broad hump in resistivity does not originate from the structural/AFM transition. The Hall effect and specific heat data are also consistent with this conclusion.