Effect of Pr-doping on magnetic and transports in YBa2Cu3O7-δ single crystal superconductor

In cuprate oxide YBCO superconductor, Pr-doping is an interesting project for a long time. The reason is that many experiments have shown that of all the rare earth elements, only Ce, Pr and Tb are exceptive, does not result in superconducting samples while with the same crystal structure as other Y123 superconductors. Here, CeBa2Cu3O7-δ and TbBa2Cu3O7-δ isn't crystalline stable, while Y1-xPrxBa2Cu3O7-δ(YPr123 systems) is easily formed in single-phase structure for all Pr content x=0.0-1.0. Therefore, to understand the question why PrBa2Cu3O7-δ(Pr123) is not superconductor is possibly essential to help to determine the nature of the superconductivity. The typical general results for Pr substitution are that there are a monotonic decrease in Tc and eventually a metal-insulator transition with increasing Pr concentration and that there are also ion size effect which shows that in R1-xPrxBa2Cu3O7-δ (R=Rare Earth), Pr suppressed superconductivity more seriously as the rare earth's radius increase. Theoretically, some models, such as magnetic pair breaking, hole filling, carrier localization, and so on, have been proposed to explain the phenomena above. Magnetic and pinning force behavior is a kind of important characteristics in both conventional superconductor and layered cuprate superconductor. Studies of flux behavior in superconductor are of interest from the viewpoints of both fundamental research and practical application. In order to explain the anomalous behavior of Pr123, in the present work, the magnetization and flux pinning results at various temperatures are reported for Y0.93Pr0.07Ba2Cu3O7-δ (YPBCO) single crystals. The samples were prepared by top-seeded solution growth method. The magnetic field dependence of critical current density Jc, pinning force density Fp and the phase diagram are also given for YPBCO single crystals. The results show that the value of the ratio of the maximum pinning force field vs irreversibility field is at around 0.333. Flux pinning mechanisms is also discussed in different magnetic field by the scaling function as well as the ratio of the pinning force field at Hon and Hpeak. The results are compared with doping free YBCO sample, which probably explains that Pr suppresses the superconductivity.