Crystal structures and superconducting properties of metallic double-chain based cuprate Pr2Ba4Cu7O15-delta

We demonstrated the lattice structures and the superconducting phases of metallic double-chain based cuprate Pr2Ba4Cu7O15-delta exhibiting higher Tc. After the oxygen heat treatment on citrate pyrolysis precursors, their reduction treatment followed by a quench procedure caused higher Tc samples with 26.5-30 K. The crystal structural parameters for the superconducting sample (delta = 0.81) were analyzed from the powder synchrotron X-ray diffraction data using RIETAN-FP program. The effect of magnetic field on the superconducting phase of these samples with different oxygen defects (delta =0.73, 0.81 and 0.87) was examined, for our understanding of the superconducting magnetic field-temperature phase diagram. For delta = 0.87 sample with Tc = 30 K, the resistive critical field Hc* was estimated to be 13 T at 4.2 K. The oxygen deficiency dependence on Tc,on for our samples was compared with the data of several other groups.Comment: 8 pages, 6 figure