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

Abstract

The crystal structure of polycrystalline PbBaSrPrCu 3 O 8 was studied using high resolution neutron diffraction. Rietveld refinement of the diffraction pattern shows that the compound crystallizes into the Tl 2 Ba 2 YCu 2 O 8 2212-type structure. The Pb and Cu atoms in the two ͑Pb,Cu͒O layers are randomly mixed to form two ͑Pb 0.5 Cu 0.5 ͒O layers, and the Ba and Sr atoms are also randomly mixed to form two ͑Ba 0.5 Sr 0.5 ͒O layers, resulting in ͑Pb 0.5 Cu 0.5 ͒ 2 ͑Ba 0.5 Sr 0.5 ͒ 2 PrCu 2 O 8 . 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 1/2͖, ͕1/2 1/2 3/2͖, and ͕1/2 1/2 5/2͖ positions. The Pr spins order at T N Ϸ 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 T N is also clearly observed in ac susceptibility measurements.

Chapter 199 Neutron scattering studies of lanthanide magnetic ordering

“…Again there can be no Cu chain magnetism, and there is a high observed T N for the Pr. The Pb 2 Sr 2 PrCu 3 O 8 material (Hsieh et al 1994b, Lin et al 1997) is somewhat different in that it has no oxygen in the Cu chain layer, while the properties of the Pr are quite similar to the other systems. Finally, we note that the related BaPrO 3 material, which obviously has no complications of Cu ordering of any kind, exhibits a similar Pr ordering temperature and reduced moment (Rosov et al 1992b) as for the cuprates.…”