SYSTEMATIC VARIATION OF T-N(PR) FOR THE 2-CUO2-LAYER CUPRATE M212 (M=1,2,3) SYSTEMS

The systematic variation of-anomalous Pr antiferromagnetic ordering te mperature T-N(Pr) for the two-CuO2-layer cuprate system MA(2)PrCu(2)O( y) (M=Cu, Hg, T1, Pb; A=Ba, Sr) was verified through the observation o f a new Hg-1212 HgSr2PrCu2O6+delta tetragonal compound with a T-N(Pr) of 6 K and a Pr-O bond length of 2.492 Angstrom between Pr and oxygen in the adjacent CuO2 layers. For the tetragonal/orthorhombic 1212 comp ounds including the PrBa2Cu3O7-y system, T-N(Pr) was found to decrease monotonically with increasing Pr-O distance. The importance of Pr-O-P r superexchange magnetic coupling is expected for all two-CuO2-layer M (m)A(2)PrCu(2)O(y) m212-type (m=1, 2, 3) compounds. A similar Pr anoma ly in the 2212-type system was first observed on me new tetragonal (Pb 0.5Cu0.5)(2)(Ba0.5Sr0.5)(2)PrCu2O8 compound With a high T-N(Pr) of 9 K . (C) 1996 American Institute of Physics.