LOCAL LATTICE INSTABILITY AND STRIPES IN THE CUO2 PLANE OF THE LA1.85SR0.15CUO4 SYSTEM BY POLARIZED XANES AND EXAFS

Temperature-dependent polarized Cu K-edge x-ray absorption has been us ed to investigate local structural distortions in the CuO2 plane of th e La1.85Sr0.15CuO4 system. The Cu-O pair distribution shows the presen ce of a minority phase containing CuO6 octahedra characterized by a sh orter Cu-O(apical) bond (Delta R similar to-0.1 Angstrom) and two long er Cu-O(planar) bonds (Delta R similar to+0.08 Angstrom) and a tilting angle of 16 degrees+/-2 degrees. The temperature-dependent distortion s show a maximum around T (similar to 1.6T(c)) and a minimum at T-c ( similar to 35 K). The The data show the coexistence of two types of do ped charges in different stripes in the superconducting phase.