X-ray absorption study of oxygen configurations in YBa2Cu3O7-δ single crystals annealed by two step heat treatments

Oxygen configurations on Cu-O basal planes in YBa2Cu3O7-delta (Y123) single crystals annealed by two step heat treatments were evaluated using extended X-ray absorption fine structure (EXAFS) spectroscopy in order to investigate the effects of the oxygen configurations on Cu-O basal planes on the peak effects in the J(c)-H curves with H\\c-axis for the single crystals. The peak intensity in the magnitude of the Fourier transform and Debye-Waller parameters (sigma(2)) for the crystals annealed by the two step heat treatments, which corresponded to the neighbor O atoms around Cu atoms, were dependent on their heat treatment conditions. Furthermore, the Debye-Waller parameters (sigma(2)) for the crystals after annealing at the second heat treatment step showed the same tendency as those for the crystals after annealing at the first heat treatment step. These results suggested that the oxygen configurations on Cu-O basal planes in the crystals after annealing at the second heat treatment step were strongly affected by those after annealing at the first heat treatment step, and that the peak effects in the J(c)-H curves were strongly affected by the disorder of the oxygen configurations on Cu-O basal planes. (C) 1999 Elsevier Science B.V. All rights reserved.