Structural effect on the static spin and charge correlations in La_1.875Ba_0.125-xSr_xCuO₄

We report the results of elastic neutron-scattering measurements performed on 1/8-hole-doped La_1.875Ba_0.125-xSr_xCuO₄ single crystals with x=0.05, 0.06, 0.075, and 0.085. In the low-temperature less-orthorhombic [(LTLO), Pccn symmetry] phase, the charge-density-wave (CDW) and spin-density-wave (SDW) wave vectors were found to tilt in a low-symmetric direction with one-dimensional anisotropy in the CuO₂ plane, while they were aligned along the high-symmetry axis in the low-temperature tetragonal (P4₂/ncm symmetry) phase. The coincident direction of two wave vectors suggests a close relation between CDW and SDW orders. The SDW wave vector systematically deviates from the Cu-O bond direction in the LTLO phase upon Sr substitution and the tilt angle in the LTLO phase is smaller than that in the low-temperature orthorhombic phase (Bmab symmetry) with comparable in-plane orthorhombic distortion. These results demonstrate a correlation between the corrugated pattern of the CuO₂ plane and the deviations.