ION-SIZE EFFECT ON TN IN (R1-XPRX)BA2CU3O7-Y SYSTEMS (R=LU, YB, TM, ER, Y, HO, DY, GD, EU, SM, AND ND)

We conducted a detailed study of the structure and magnetic properties of (R1-xPrx)Ba2Cu3O7 sintered samples, where R = Lu, Yb, Tm, Er, Y, H o, Dy, Gd, Eu, Sm, and Nd for x = 0.5-1.0. We found that the temperatu re dependence of the dc susceptibility follows the Curie-Weiss law in the temperature range 20-300 K and the paramagnetism of the Pr and R s ublattices exist independently of one another. The antiferromagnetic o rdering temperature T(N) of Pr ions decreases monotonically with incre asing R concentration (1-x). At a given x, T(N) is R-ion-size dependen t. The slope in the T(N) vs x curve is steeper for ions with smaller i onic radii. The observed results are interpreted in terms of the hybri dization between the local states of the Pr ion and the valence-band s tates of the CuO2 planes.