Nuclear-spin evidence of insulating and antiferromagnetic state of CuO2 planes in superconducting Pr2Ba4Cu7O15−δ2022 · Abstract In contrast to the “Pr-issue” that neither PrBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub> (Pr123) nor PrBa<sub>2</sub>Cu<sub>4</sub>O<sub>8</sub> (Pr124) shows superconductivity (SC), we have observed 100%-fraction of SC in an oxygen-reduced Pr<sub>2</sub>Ba<sub>4</sub>Cu<sub>7</sub>O<sub>15−δ</sub> (Pr247) which has a hybrid structure that Pr247 = Pr123 + Pr124. It is found that Cu nuclear-spin signals from the CuO<sub>2</sub> planes observed at 300 K are completely wiped out at 2 K. Instead, the plane signals at 2 K are observed at higher frequencies. This indicates that, despite the bulk SC, the CuO<sub>2</sub> planes in Pr247 are found to be in an insulating and antiferromagnetically ordered state.
