COUPLING-CONSTANT VERSUS DENSITY-OF-STATES IN LA2-XSRXCUO4 AS REVEALED BY EPR OF GD SPIN PROBES

By analyzing the Korringa contribution to the EPR linewidth of Gd3+ ions doped to high-quality La2-xSrxCuO4 samples with various Sr content (x = 0.08-0.35) a dependence of the density of states N(E(F)) on x has been extracted. The analysis of the observed dependence together with that for the critical temperature T(c)(x) enabled us to study the relation between the coupling constant lambda and N(E(F)) in course of Sr doping. We found that up to the optimum Sr concentration of x = 0.15 the coupling constant lambda increases correspondingly to increasing of the density of states. At the same time lambda rapidly decreases in the overdoped region (x > 0.15) while N (E(F)) continuously grows. The possible reasons for such a behavior are discussed.