RESISTIVE TRANSITION, MAGNETORESISTANCE, AND ANISOTROPY IN LA2-XSRXCUO4 SINGLE-CRYSTAL THIN-FILMS

The temperature dependence of the resistivity rho(T) in the vicinity of the superconducting transition temperature T(c) has been measured for thin-film single crystals of La(2-x)Sr(x)CuO4 as a function of an applied magnetic field, both parallel and perpendicular to the c axis. The resistive transition exhibits characteristic behavior, depending on the Sr concentration x, when a field is applied. For small x the application of a field causes a significant broadening of the resistive transition - a behavior thought to be typical of high-T(c) cuprate superconductors - while for x exceeding 0.15, it simply causes a parallel shift of the curves to lower temperatures. From the analysis of the magnetoresistance above T(c) based on the theory of field-dependent fluctuation conductivity for layered materials, it is shown that the behavior of the field-induced resistive transition can be ascribed to the flux motion, especially when H perpendicular-to c. The analysis also shows that the out-of-plane Ginzburg-Landau coherence length zeta-c(0) increases systematically with x from 0.55 angstrom at x = 0.08 to 3 angstrom at x = 0.3, while the in-plane Ginsburg-Landau coherence length zeta-ab(0) is almost constant and zeta-ab(0) = 31-33 angstrom, irrespective of the value of x as long as T(c) remains high. The anisotropy zeta-ab(0)/zeta-c(0) estimated from these results exceeds 50 at low Sr concentrations and is still larger than 15 even for x > 0.1.