Abstract
The magnetic ordering of the Pr ions in Pb 2 Sr 2 PrCu 3 O 8 has been studied using neutron-diffraction and ac-suspectibility measurements. An imperfect three-dimensional magnetic ordering of the Pr spins was observed at a temperature well below its Neel temperature of T N ≊7 K. The magnetic intensities observed at T=1.4 K can be explained by assuming long-range order in the ab plane with short-range correlations, of correlation length ξ c =20 Å, along the c axis and a moment directed along the c-axis direction. The magnetic ordering is 2D in nature, and the basic magnetic structure consists of nearest-neighbor spins that are aligned antiparallel along all three crystallographic directions. The magnetic transition is also evident in the ac-susceptibility versus temperature measurements, where a cusp that is typical of antiferromagnetic ordering is clearly observed, which matches the T N obtained by neutron diffraction.