SUPERCONDUCTING AND MAGNETIC-PROPERTIES OF TLSR2CA(1-X)R(X)CU(2)O(7) [R=PR,TB]

The magnetic and superconducting properties of the TISr2Ca1-xRxCu2O7 [R=Pr (x=0.2-1.0); Tb (x=0.6 and 1.0)] system are reported. The observation of superconductivity in TISr2Ca0.4Pr0.6Cu2O7 (Tc=74 K) suggests that the Pr ions are in the trivalent state. The value of the effective magnetic moment, μeff=3.15μB, for the TISr2Ca0.4Pr0.6Cu2O7 compound, lies between the free-ion values expected for Pr3+ (3.58 μB) and Pr4+ (2.54μB). The reduced value of μeff for the Pr3+ ion is explained in terms of crystal-field effects. For TISr2TbCu2O7, the Tb magnetic moments order antiferromagnetically at 7.0 K, which is the highest magnetic ordering temperature among the known Tb-containing high-Tc related compounds. Superconductivity (Tc=74 and 62 K) and antiferromagnetic ordering (TN=5 and 6.2 K) coexist in TISr2Ca0.4R0.6Cu2O7 with R=Pr and Tb, respectively. © 1995 The American Physical Society.