Crystal structure and magnetic ordering of Pr in (Pb0.5Cu0.5)2(Ba0.5Sr0.5)2PrCu2O8

Abstract

The crystal structure of polycrystalline PbBaSrPrCu3O8 was studied using high resolution neutron diffraction. Rietveld refinement of the diffraction pattern shows that the compound crystallizes into the Tl2Ba2YCu2O8 2212-type structure. The Pb and Cu atoms in the two (Pb,Cu)O layers are randomly mixed to form two (Pb0.5Cu0.5)O layers, and the Ba and Sr atoms are also randomly mixed to form two (Ba0.5Sr0.5)O layers, resulting in (Pb0.5Cu0.5)2(Ba0.5Sr0.5)2PrCu2O8. The magnetic ordering of the Pr ions was also studied using magnetic neutron diffraction and ac susceptibility measurements. At low temperatures, magnetic peaks presumably originating from the Pr spin ordering were observed at the {1/2 1/2 1/2 1/2}, {1/2 1/2 3/2}, and {1/2 1/2 5/2} positions. The Pr spins order at TN≈9 K with the moment direction along the c axis and the nearest-neighbor spins coupled antiferromagnetically. A cusp associated with the antiferromagnetic ordering at TN is also clearly observed in ac susceptibility measurements.