Absence of superconductivity in (Pr 1.5Ce 0.5)Sr 2Cu 2NbO 10—A general correlation with magnetic ordering

Abstract

(Pr 1.5Ce 0.5)Sr 2Cu 2NbO 10 is found to be an insulating analog to (Nd 1.5Ce 0.5)Sr 2Cu 2NbO 10, (Sm 1.5Ce 0.5)Sr 2Cu 2NbO 10 and (Eu 1.5Ce 0.5)Sr 2Cu 2NbO 10 which have superconducting transition temperatures near 28 K. (Pr 1.5Ce 0.5)Sr 2Cu 2NbO 10 is also observed to display two magnetic ordering transitions, near 15 K and 50 K, which are not observed for the Nd, Sm or Eu based materials. This compound is a new example of the absence of superconductivity in a PrBa 2Cu 3O 7 related structure which exhibits an unusually high magnetic ordering temperature relative to the other members of the rare earth series. An argument is made for a general correlation between the absence of superconductivity and the presence of magnetic ordering in these structures. The observation of this correlation in the (R 1.5Ce 0.5)Sr 2Cu 2NbO 10 system is compared to similar observations in RBa 2Cu 3O 7 and RBa 2Cu 2NbO 8. The physical basis for the general nature of this correlation is discussed in terms of f electron hybridization and the unusual crystal field splitting observed for the Pr ion in the YBCO structure.