SYNTHESIS AND MAGNETISM OF (HG0.7BI0.3)SR(2)RCU(2)O(6+DELTA) (R=PR, ND, AND GD) SYSTEM

The problems of making phase-pure (Hg0.7Bi0.3)Sr(2)RCu(2)O(6+delta) sy stem, with R = Pr, Nd, and Gd, are discussed in detail. Complete subst itution of these three rare earths at the Ca site is realized in this system. We identify the phase responsible for the magnetism to be simi lar to that of TlBa2CaCu2O6+delta (so-called 1212 phase) with a space group of P4/mmm and lattice constants of a similar to 3.8 Angstrom and c similar to 12 Angstrom. Magnetic-susceptibility (chi) measurements on these samples give an effective moment close to +3 for Gd, lower th an +3 for Nd, but intermediate between those of +3 and +4 for Pr. No a nomalous rare-earth (Pr, Nd, Gd) antiferromagnetic orderings were obse rved down to 5 K.