Properties that change as superconductivity disappears at high-doping concentrations in La2-xSrxCuO4

Abstract

In the system La2-xSrxCuO4, as x and p (the [CuO2]p-2 charge) are increased, the superconducting transition temperature first increases, then peaks becoming nonsuperconducting for x0.26. We report here a search for changes in physical properties at the values of x where Tc 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 Ts also decreases with increasing x and becomes unobservable for x0.19, suggesting that this structural transition itself is unrelated to the disappearance of superconductivity that occurs at higher doping levels. The magnetic spin susceptibility spin(T) generally rises gradually with increasing doping (reflecting decreasing spin-spin interactions), reaches a maximum near x1/40.25, and then decreases. There is a weak peak in spin(T) as a function of temperature at T=Tmax. As a function of increasing x,Tmax falls to zero near x1/40.25. These two observations might be related to the disappearance of superconductivity, since all three occur near the same value of Sr content x. © 1989 The American Physical Society.