${\mathrm{PrBa}}_2$${\mathrm{Cu}}_2$${\mathrm{NbO}}_8$ (PrBCNO) is an insulator analogous to the ${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ system having a similar structure but with ${\mathrm{NbO}}_2$ planes replacing the CuO chains. Single-phase polycrystalline samples of RBCNO have been synthesized with R=La, Pr, or Nd. These materials were characterized using magnetization, thermal gravimetric analysis in different atmospheres, x-ray diffraction, and Raman spectroscopy. The PrBCNO samples show a signature in the magnetization of a magnetic ordering at 12 K. No such magnetic phase transition is observed down to 2 K in ${\mathrm{NdBa}}_2$${\mathrm{Cu}}_2$${\mathrm{NbO}}_8$.

• Received 3 June 1992

DOI:https://doi.org/10.1103/PhysRevB.46.11986