Stripe structure of the ${\mathrm{CuO}}_2$ plane in ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathit{y}}$ by anomalous x-ray diffraction

The modulated structure of the ${\mathrm{CuO}}_2$ plane in ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{8+\mathit{y}}$ superconductor has been solved by Cu K-edge anomalous x-ray diffraction. The displacement of Cu ions along the c axis shows the largest amplitude and anharmonic character. The results show flat stripes of ${\mathrm{CuO}}_2$ lattice of width L=15.5 Å with long Cu-Bi distances that are separated by stripes of bent ${\mathrm{CuO}}_2$ plane and shorter Cu-Bi distances. In each ${\mathrm{CuO}}_2$ bilayer the flat stripes in a first layer are close to the bent stripes in the second layer, suppressing the electronic coupling between the two adjacent planes. © 1996 The American Physical Society.