Neutron scattering study of the antiferromagnetic ordering in YBa 2Cu 3O 6+x powder and single crystal samples

Abstract

Neutron diffraction experiments have been performed on powder and single crystal (2×5×2×1.5 mm 3) samples of YBa 2Cu 3O 6+x compounds. The reduced compound YBa 2Cu 3O 6 is found to order antiferromagnetically belowT N = 420 ± 10K. The magnetic moment is about 0.6 ± 0.05 μ B on the Cu 2+ sites and aligned perpendicular to the tetragonal c-axis. The magnetic structure is characterized by an in-plane wave vector|1/2 1/2 0| and an antiferromagnetic coupling between the two CuO 2 planes of the unit cell. The addition of oxygen induces only a decrease of T N and the moment value (290 ± 10 K, 0.45 ± 0.05 μ B and 245 ± 10 K, 0.28± 0.05 μ B, for x = 0.25 ± 0.03 and 0.38 ± 0.03, respectively). The long range order disappears abruptly aroundx = 0.40.