Extended x-ray-absorption fine-structure experiment on the high-Tc superconductor YBa2Cu3O7−δ

Abstract

X-ray-absorption spectroscopy has been used to study the high-$T_c$ superconductor ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ on all three metal elements. The structure determined is consistent with diffraction results, except for some slight differences. Analysis of the yttrium K-edge x-ray-absorption fine-structure (EXAFS) experiment suggested that the Y-O distance split further into two distances at 80 K. The temperature dependence of the Cu-O bond strength indicated that the system below $T_c$ is more disordered than an Einstein model predicted. The bond strengths determined by the temperature dependence of the EXAFS Debye-Waller factor showed clearly that the Cu(2) planes are strongly coupled with each other through yttrium-oxygen bonds, and are weakly coupled to the other planes.