STRUCTURAL NEUTRON-DIFFRACTION STUDY OF A ND2CUO4-DELTA SINGLE-CRYSTAL

We report on structural neutron diffraction results obtained on a Nd2CuO4 single crystal. The same crystal was studied in both oxidized and reduced states. Structure refinements have led to an oxygen stoichiometry of 3.94(5) in the oxidized state corresponding to 0.06 oxygen deficiency in O(2) oxygen planes, the O(1) site (in CuO2 planes) being fully occupied. After reduction treatment we have shown that this oxygen deficiency remains unaffected, the oxygen removal delta=0.05 occuring only on the O(1) site. The resulting oxygen content in the reduced sample is then 3.89(4). No apical oxygen was detected in any of states. We also confirm the effective metal atoms stoichiometry (Nd/Cu=2) in both states, Cu and Nd sites being completely filled. No appreciable changes have been observed for the anisotropic thermal parameters between the two states of oxidation. A large decrease of the extinction in the crystal after the reducing treatment is observed. Further experiments are needed to clarify this point.