DOPING DEPENDENCE OF THE SPATIALLY MODULATED DYNAMICAL SPIN CORRELATIONS AND THE SUPERCONDUCTING-TRANSITION TEMPERATURE IN LA2-XSRXCUO4

Systematic low-energy neutron-scattering studies have been performed o n float-zone-grown single crystals of La2-xSrxCuO4 with x extending fr om zero doping, x = 0, to the overdoped, weakly superconducting regime , x = 0.25. For x beyond a critical doping value of x(c) approximate t o 0.05 the low-energy spin-fluctuation peak position shifts from (1/2, 1/2) to (1/2+/-delta,1/2), and (1/2,1/2+/-delta); x(c) also represents the onset concentration for superconductivity. For 0.06 less than or equal to x less than or equal to 0.12 the incommensurability delta fol lows approximately the quantitative relation delta=x. However, beyond x approximate to 0.12 the incommensurability tends to saturate around delta approximate to 1/8. The superconducting-transition temperature T -c(x) for stoichiometric samples at a given doping scales linearly wit h delta up to the optimal doping value of x. The peak momentum width o f the spin fluctuations at low energies is small throughout the superc onducting concentration region except in the strongly overdoped region . An anomalously small width is observed for x = 1/8. The incommensura te spatial modulation is found to be robust with respect to pair-break ing effects that lower T-c, such as deoxygenation of the sample or rep lacement of Cu by Zn.