UC Irvine

We have employed polarized and unpolarized neutron-diffraction techniques on both powders and single crystals to establish the nature of the magnetic order of the Cu ions in oxygen-deficient (nonsuperconducting) RBa2Cu3O6+x (R=Y,Nd). Magnetic Bragg peaks of the type (h2,k2,l) are observed that yield a magnetic structure in which the Cu spins are coupled antiferromagnetically both in the Cu-O planes as well as along the tetragonal c axis, with the spin direction in the tetragonal plane. The Néel temperature is very sensitive to the oxygen content, with TN(x1/40)500 K, while the spin configuration is independent of x. © 1988 The American Physical Society.