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

We report magnetic neutron-scattering measurements of incommensurate magnetic order in a superconducting single crystal of La1.88Sr0.12CuO4. We find that 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 magnetic order found in the low-temperature tetragonal LB1.6-xNd0.4SrxCuO4 material for which stripes of spin and charge have been observed. These observations have clear implications for any stripe model proposed to describe the static magnetism in orthorhombic La2CuO4-based superconductors.