Abstract
The crystalline structures of Tl(Ba 2-x Sr x )PrCu 2 O 7-y (x=0, 0.4, 0.8, 1.0, 1.2, 1.6, 2) were obtained at room temperature (300 K) and low temperature (100 K) from X-ray powder diffraction with Cu Kα radiation using Rietveld analysis. Tl(Ba 2-x Sr x )PrCu 2 P 7-y has an isotypical structure with TlBa CaCu O (1212) at 300 and 100 K, i.e., the tetragonal system, space group P4/mmm, Z=1. The relatioships between the PrO(1) bond lengths and the O(1)PrO(1) bond angles with the antiferromagnetic ordering temperature T (Néel temperature are discussed. The mechanism of the decrease in the antiferromagnetic ordering temperature T n as well as the nonsuperconductivity of this system are explained using the Pr(4f) and O(2p) orbital hybridization and the PrO(1) bond lengths. The suggested mechanism of PrPr coupling (interplanar PrPr distance) for the Pr ordering by a previous study is inconsistent with our experimental results. © 1994.