Neutron diffraction measurements on a highly doped single crystal of ${\mathrm{La}}_2$${\mathrm{NiO}}_{4+\mathrm{\delta }}$ (δ=0.105) reveal that below room temperature the crystal undergoes phase separation into an orthorhombic structure, with a doubled unit cell along c, and a tetragonal phase. The lattice distortion in the orthorhombic phase suggests charge-density-wave order, and related diffuse scattering is observed at room temperature. The orthorhombic phase orders antiferromagnetically below 55 K with a significant ordered moment (∼0.7${\mathrm{\mu }}_{\mathit{B}}$).

• Received 21 September 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.445