ANISOTROPIC PENETRATION DEPTH IN LA2-XSRXCUO4

The surface impedance at 10 GHz was measured systematically in single-crystal La2-xSrxCuO4 for carrier concentrations 0.09 less-than-or-equal-to x less-than-or-equal-to 0.19, from which the penetration depth lambda was determined. The anisotropy and the dependences on x and temperature T of lambda are extensively studied for the first time. The anisotropy of lambda(T = 0) decreases with increasing x, and still remains larger than 10 for x = 0.19. The out-of-plane penetration depth (lambda(ab)) has a different temperature dependence from the in-plane one (lambda(ab)). These results suggest that the electrodynamic properties in the superconducting state along the c axis can be explained by a Josephson-coupled layer model.