Observation of Pr magnetic order in PrBa{sub 2}Cu{sub 3}O{sub 7}

Neutron-diffraction experiments have been carried out to investigate the magnetic order in PrBa{sub 2}Cu{sub 3}O{sub 7}. Our neutron data indicate that the Cu spins order above 300 K. This ordering is not significantly affected at low temperatures, where new magnetic Bragg peaks develop below 17 K that must be associated with the antiferromagnetic ordering of Pr spins, with an ordered moment of 0.79(5){mu}{sub B}. This rules out the possibility recently proposed by Nehrke and Pieper [Phys. Rev. Lett. {bold 76}, 1936 (1996)] that the new magnetic Bragg peaks arise from a spin reorientation of the Cu spins and that the Pr carries essentially no moment. {copyright} {ital 1997} {ital The American Physical Society}