Abstract

In the system ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_{4}$, as x and p (the [${\mathrm{CuO}}_{2}$${]}^{\mathrm{p}\mathrm{\ensuremath{-}}2}$ charge) are increased, the superconducting transition temperature first increases, then peaks becoming nonsuperconducting for x\ensuremath{\gtrsim}0.26. We report here a search for changes in physical properties at the values of x where ${T}_{c}$ is observed to change its behavior. The in-plane lattice constants and the normal resistivity both show a continued monotonic decrease over this entire region, suggesting that no major electronic changes occur. The tetragonal-to-orthorhombic transition temperature ${T}_{s}$ also decreases with increasing x and becomes unobservable for x\ensuremath{\gtrsim}0.19, suggesting that this structural transition itself is unrelated to the disappearance of superconductivity that occurs at higher doping levels. The magnetic spin susceptibility ${\ensuremath{\chi}}_{\mathrm{spin}(\mathrm{T}}$) generally rises gradually with increasing doping (reflecting decreasing spin-spin interactions), reaches a maximum near x\ensuremath{\sim}0.25, and then decreases. There is a weak peak in ${\ensuremath{\chi}}_{\mathrm{spin}(\mathrm{T}}$) as a function of temperature at T=${T}_{\mathrm{max}}$. As a function of increasing x,${T}_{\mathrm{max}}$ falls to zero near x\ensuremath{\sim}0.25. These two observations might be related to the disappearance of superconductivity, since all three occur near the same value of Sr content x.