Li substitutes for Cu in ${\mathrm{La}}_2$${\mathrm{CuO}}_4$ up to the limiting stoichiometry ${\mathrm{La}}_2$${\mathrm{Cu}}_{0.5}$${\mathrm{Li}}_{0.5}$${\mathrm{O}}_4$, which has superstructure order. The effects of this in-plane hole doping on the structural and magnetic properties of ${\mathrm{La}}_2$${\mathrm{CuO}}_4$ are very similar to those due to Sr substitution. The tetragonal-orthorhombic structural phase transition occurs, for a given amount of Sr or Li, at nearly the same temperature, and the in-plane lattice constant of ${\mathrm{La}}_{2\mathrm{-}\mathit{y}}$${\mathrm{Sr}}_{\mathit{y}}$${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Li}}_{\mathit{x}}$${\mathrm{O}}_4$ at room temperature depends only on the combined hole count (x+y) and not on the individual Sr or Li concentration. Long-range magnetic order is destroyed upon substituting 3% Li for Cu, analogous to the effect of Sr substitution on ${\mathit{T}}_{\mathrm{N}\mathrm{é}\mathrm{el}}$. However, the holes introduced by Li substitution are bound. The resistivity as a function of temperature is nonmetallic for all Li concentrations. © 1996 The American Physical Society.

• Received 18 June 1996

DOI:https://doi.org/10.1103/PhysRevB.54.12014