Incommensurate geometry of the elastic magnetic peaks in superconducting La1.88Sr0.12CuO4

We report magnetic neutron-scattering measurements of incommensurate magnet ic order in a superconducting single crystal of La1.88Sr0.12CuO4. We find t hat the incommensurate wave vectors which describe the static magnetism do not lie along high-symmetry directions of the underlying CuO2 lattice. The positions of the elastic magnetic peaks are consistent with those found in excess-oxygen doped La2CuO4+y. This behavior differs from the precise magne tic order found in the low-temperature tetragonal LB1.6-xNd0.4SrxCuO4 mater ial for which stripes of spin and charge have been observed. These observat ions have clear implications for any stripe model proposed to describe the static magnetism in orthorhombic La2CuO4-based superconductors.