Cu-spin dynamics at zigzag chain of superconducting and nonsuperconducting Pr247 compounds

We present Cu nuclear quadrupole resonance (NQR) results for both superconducting Pr2Ba4Cu7O14.5 (Pr247_S) and nonsuperconducting Pr2Ba4Cu7O15 (Pr247_NS). We found that: (1) Below Tc = 18 K, the 1/T1T of the double chains in Pr247_S is appreciably smaller than that of Pr247_NS. On the other hand, the planar-site signals of Pr247_S disappear below 285 K, indicating the transferring into magnetically ordered state. To our knowledge, this is the first experimental evidence that the superconductivity of Pr247_S is driven and realized at the double chains, while the CuO2 planes remain magnetically ordered. (2) For Pr247_NS, the temperature dependence of 1/T1 and 1/T2 at the double chains showed a pronounced peak at around 110 K and 50 K, respectively, which is similar to the reported behavior for Pr124 compound. In contrast, for Pr247_S, no anomalies are observed in 1/T1 or 1/T2. This suggests that, above Tc, the double chains of Pr247_S should be in the normal metallic state, unlike the case of Pr247_NS or Pr124.