UC Irvine

Li substitutes for Cu in (Formula presented)(Formula presented) up to the limiting stoichiometry (Formula presented)(Formula presented)(Formula presented)(Formula presented), which has superstructure order. The effects of this in-plane hole doping on the structural and magnetic properties of (Formula presented)(Formula presented) 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 (Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) 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 (Formula presented). 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.