Charge and spin ordering inLa2−xSrxNiO4.00withx=0.135 and 0.20

We report neutron-scattering experiments that reveal coupled incommensurate peaks arising from magnetic as well as charge ordering at low temperatures (T≤100 K) in stoichiometric ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{NiO}}_{4+\mathrm{\delta }}$ (δ=0.00) crystals. In contrast with the long-range ordering of holes and spins observed recently in ${\mathrm{La}}_2$ ${\mathrm{NiO}}_{4.125}$, the correlations are short ranged in Sr-doped ${\mathrm{La}}_2$ ${\mathrm{NiO}}_4$ and the incommensurability ɛ is 0.25 and 0.12 for x=0.20 and 0.135, respectively. Based on our study and previous reports on ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{NiO}}_{4+\mathrm{\delta }}$, the modulation wave vector appears to be a sensitive function of net hole concentration, p=x+2δ. The magnetic correlation length increases with doping and the incommensurability follows the simple relationship ɛ≊p. DOI: http://dx.doi.org/10.1103/PhysRevB.51.12742 © 1995 The American Physical Society