The problems of making phase-pure ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$R${\mathrm{Cu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$ systems, with R=Y, Pr, and Tb, are discussed in detail, particularly in the case of Pr and Tb. Complete substitution of these three rare earths at the Ca site is realized in this system. The c lattice parameter of the rare-earth-containing material decreases in comparison with that of the pure undoped ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$. On-site ionic size differences and increased oxygen content due to aliovalent substitution are the possible causes of the decreased c lattice parameter. Magnetic-susceptibility (χ) measurements on these samples give an effective paramagnetic moment close to that of 3+ for Tb but intermediate between those of 3+ and 4+ for Pr. A change in slope in the ${\mathrm{\chi }}^{\mathrm{-}1}$ vs T curve for the Y compound at ∼295 K and a dip in the same for the Pr compound at ∼330 K may be indicative of the antiferromagnetic ordering of the Cu moments in these compounds.

• Received 2 December 1994

DOI:https://doi.org/10.1103/PhysRevB.51.9379