ANISOTROPIC MAGNETIC AND CALORIMETRIC PROPERTIES OF THE INCOMMENSURATE MODULATED BI2SR2PRCU2O8-CRYSTAL(DELTA SINGLE)

Anisotropic magnetic and calorimetric properties of the incommensurate modulated Bi2Sr2PrCu2O8+delta single crystals have been reported. No Pr magnetic ordering was observed down to 0.5 K in specific heat data and in anisotropic magnetic susceptibility measurements for magnetic f ield applied along the single crystal orthorhombic ab-plane or c-axis. In comparison, isostructural Gd polycrystalline sample Bi2Sr2GdCu2O8delta exhibits an antiferromagnetic order with Neel temperature T-N(Gd ) of 1.7 K. The Bi2Sr2PrCu2O8+delta compound represents the first exam ple of no Pr anomaly observed for all two-CuO2-layers Pr cuprates M(m) A(2)PrCu(2)O(y) (M = Hg, Pb, TI, Pi, Nb, Cu; A = Pa, Sr; m = 1, 2, 3). The lack of Pr ordering is believed to be due to a very weak quasi-2D Pr-O-Pr superexchange interaction caused by the strong structural mod ulation.