REVERSIBLE MAGNETIC-PROPERTIES OF (LA1-XSRX)2CUO4 SINGLE-CRYSTALS WITH 0.05-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.10

Systematic magnetization measurements were made to study reversible magnetic properties of a series of high-quality, large single crystals of (La1-xSrx)2CuO4 over a composition range of x = 0.05-0.10, with magnetic fields parallel to the c axis. A method of data analysis, based on the variational model developed by Hao and Clem, was used for the determination of various superconducting parameters of this family. We fit the temperature dependence of the thermodynamic critical field H(c)(T) data, which was obtained in the temperature region where the thermodynamic fluctuation is insignificant, with the BCS or an empirical function for H(c)(T). We found that a crystal (x = 0.077), which has the highest T(c) (congruent-to 35.0 K), shows a maximum in the value of H(c)(0) (= 2510+/-80 Oe) and a minimum in the value of lambda(ab)(0) (= 2545+/-40 angstrom) for the range of x that we have studied. We also observed rather close values of coherence length in the ab plane [xi(ab)(0) approximately 32 angstrom] for all (La1-xSrx)2CuO4 single crystals that we studied.