Nuclear-spin evidence of insulating and antiferromagnetic state of CuO2 planes in superconducting Pr2Ba4Cu7O15−δ

Abstract

Abstract In contrast to the “Pr-issue” that neither PrBa2Cu3O7 (Pr123) nor PrBa2Cu4O8 (Pr124) shows superconductivity (SC), we have observed 100%-fraction of SC in an oxygen-reduced Pr2Ba4Cu7O15−δ (Pr247) which has a hybrid structure that Pr247 = Pr123 + Pr124. It is found that Cu nuclear-spin signals from the CuO2 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 CuO2 planes in Pr247 are found to be in an insulating and antiferromagnetically ordered state.