ION-SIZE EFFECT ON T(M) AND T(C) IN (R1-XPR(X))BA2CU3O7 SYSTEMS (R = YB, TM, ER, HO, DY, GD, EU, SM, ND AND Y)

The magnetic ordering temperatures T(m) of Pr ions in (R1-xPrx)Ba2Cu3O 7 systems (R = Yb, Tm, Er, Ho, Dy, Gd, Eu, Sm, Nd and Y) with x = 0.5 - 1.0 were measured. We observe that T(m) decreases monotonically with increasing R concentration. At constant x, T(m) is R ion-size depende nt. The slope in the T(m) vs. x is steeper for ion with smaller ionic radius. In comparison with the ion-size effect on the superconducting transition temperatures T(c) in these systems, the observed results ca n be qualitatively interpreted in terms of the hybridization between t he local states of Pr ion and the conduction band states of the CuO2 p lanes.