Synthesis, structural, and transport properties of the hole-doped superconductor Pr1-xSrxFeAsO

Superconductivity was achieved in PrFeAsO by partially substituting Pr3+ with Sr2+. The electrical transport properties and structure of this superconductor Pr1-xSrxFeAsO at different doping levels (x=0.05 similar to 0.25) were investigated systematically. It was found that the lattice constants (a and c axes) increase monotonously with Sr or hole concentration. The superconducting transition temperature at about 16.3 K (95% rho(n)) was observed around the doping level of 0.20 similar to 0.25. A detailed investigation was carried out in the sample with doping level of x=0.25. The domination of holelike charge carriers in this material was confirmed by Hall-effect measurements. The magnetoresistance (MR) behavior can be well described by a simple two-band model. The upper critical field of the sample with T-c=16.3 K (x=0.25) was estimated to be beyond 45 T. Our results suggest that the hole-doped samples may have higher upper critical fields comparing to the electron-doped ones, due to the higher quasiparticle density of states at the Fermi level.