RAMAN AND MICROWAVE SURFACE IMPEDANCE MEASUREMENTS IN THE ORGANIC SUPERCONDUCTOR KAPPA-ET2CU[N(CN)(2)]BRXCL1-X

We report a Raman study of CH2 and C=C vibrations for single crystals of the organic superconductor kappa-Et2Cu[N(CN)(2)]BrxCl1-x (nominal v alue x=.5) in both the normal and superconducting states (T-c=11.3 K). The average charge transfer rho=0.5 is estimated from the frequency o f the C=C ring stretching Raman mode nu(3)(A(g)). Raman results are di scussed in connection with our previous study of the normal and superc onducting states of Et2Cu[N(CN)(2)]Br. High sensitivity microwave surf ace impedance is also studied. The microwave resistance R-s and microw ave reactance X-s are reported as a function of temperature in order t o complement our Raman experiments and to determine precisely the crit ical temperature T-c and the type of superconductivity.