X-ray scattering measurements of the low-temperature structure of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_{1+x}{\mathrm{MnO}}_4$ ( $0.33\le x\le 0.67$) indicate the existence of three distinct regions: a disordered phase $(x<\mathrm{}0.4\mathrm{})$, a charge-ordered phase $(x\ge 0.5)$, and a mixed phase $(0.4\le x<\mathrm{}0.5\mathrm{})$. For $x>\mathrm{}0.5\mathrm{}$, the modulation vector associated with the charge order is incommensurate with the lattice and depends linearly on the concentration of $e_g$ electrons. The primary superlattice reflections are strongly suppressed along the modulation direction and the higher harmonics are weak, implying the existence of a largely transverse and nearly sinusoidal structural distortion, consistent with a charge-density wave of the $e_g$ electrons.

• Received 19 December 2000

DOI:https://doi.org/10.1103/PhysRevLett.87.095502