Anisotropic AC field screening of superconducting /spl kappa/-(BEDT-TFF)/sub 2/ Cu[N(CN)sub 2/]X (X=Br, Cl)

Summary form only given. The family of title compounds, which gives the highest transition temperature to date among the organic superconductors, is characterized by the two-dimensionality as evidenced by torque measurements or vortex lock-in effect. We measured the ac susceptibility of /spl kappa/-(BEDT-TTF)/sub 2/-Cu[N(CN)/sub 2/]Cl (Cl-salt) under hydrostatic pressure of 300-700 bar around the superconducting transition in different configurations of ac and dc field and conducting plane at frequency of 2-3 MHz. In this pressure region we confirmed the reentrant superconducting transition and non-metal phase enhancement in high dc magnetic field in agreement with resistivity measurement [1]. We compare these results with the case of of /spl kappa/-(BEDT-TTF)/sub 2/-Cu[N(CN)/sub 2/]Br (Br-salt) under ambient pressure measured in the same conditions. The superconductivity realized in Cl-salt is found to be similar one to Br-salt with respect to the ac field screening. We discuss the results for both salts based on the critical state model paying attention to the vortex dynamics in the anisotropic superconductor.