Spin-stripe density varies linearly with hole content in single-layer   Bi2201 cuprate
  We have performed inelastic neutron scattering measurements on the single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4 and 0.5, a doping range that spans the spin-glass (SG) to superconducting (SC) phase boundary. The doping evolution of low energy spin fluctuations was found to be characterized by a change of incommensurate modulation wave vector from the tetragonal [110] to [100]/[010] directions, while maintaining a linear relation between the incommensurability and the hole concentration, delta p. In the SC regime, the spectral weight is strongly suppressed below 4 meV. Similarities and differences in the spin correlations between Bi2201 and the prototypical single-layer system La2-xSrxCuO4 are discussed. 
M. Enoki, M. Fujita, T. Nishizaki, S. Iikubo, D. K. Singh, S. Chang,   J. M. Tranquada, and K. Yamada
cond-mat.str-el