Local structure in single crystals of La-based high T_ccuprates

The buckling of CuO2 plane in single crystals of La_2-xSr _xCuO₄ (LSCO) [x 0.08] and La_2-x-yBaySr _xCuO₄ (LBSCO) [x 0.06 , y 0.065] was directly observed by high-field Cu-NMR spectra. The split pattern in the NMR spectra of LSCO [x 0.08] shows that the local structure is Low Temperature Orthorhombic (LTO) like at low temperature, consistent with the results reported by diffraction experiments. In LBCO [x 0.08], the local structure is Low Temperature Tetragonal (LTT) like, while the averaged structure is reported to be LTO. In LBSCO, the local structure is found to be either LTT-like or Low Temperature Less- Orthorhombic (LTLO) between 35 and 70 K, while the averaged structure is reported to be LTO. With decreasing temperature, the resonance peak disappeared below 35 K, indicating the appearance of Charge Density Wave (CDW) or Spin Density Wave (SDW).