DISAPPEARANCE OF SUPERCONDUCTIVITY AND ANOMALOUS MAGNETIC-ORDERING OF PRBA2CU3O7-Y

Results of the depression of superconductivity by substitution of Pr in R0.8Pr0.2Ba2Cu3O7-y (R = Y and rare earths) and the effect of Fe, Co, Ni, Zn, and Ga substitution on the structural, magnetic and electrical properties of PrBa2Cu3O7-y are reported. The DELTAT(c), where DELTAT(c) = Tc(RBa2Cu3O7-y) - Tc(R0.8Pr0.2Ba2Cu3O7-y), strongly depends on the ionic radius of rare-earth elements. It is interpreted that the strong hybridization between Pr 4f-electrons and conduction holes in Cu-O2 planes plays a crucial role in the quenching of superconduvtivity in PrBa2Cu3O7-y. An almost opposite behavior in the depression of T(N) by the metal substitution observed in PrBa2Cu3O7-y and GdBa2Cu3O7-y indicates possibly different magnetic coupling mechanisms in these compounds. Meanwhile, the more Cu(1) site disorder is introduced, the more effective in suppressing T(N) and the more insulating behavior are observed. It suggests that the Cu-O chain transport would play a key role in the magnetic coupling of PrBa2Cu3O7-y.