S. Wanka et al., SPECIFIC-HEAT AND CRITICAL FIELDS OF THE ORGANIC SUPERCONDUCTOR BETA''-(BEDT-TTF)(2)SF5CH2CF2SO3, Physical review. B, Condensed matter, 57(5), 1998, pp. 3084-3088
We report on specific-heat, magnetization, and ac-susceptibility measu
rements of beta ''-(BEDT-TTF)(2)SF5CH2CF2SO3, an organic superconducto
r with T-c = 4.5 K, where BEDF-TTF stands for bis(ethylenedithio)-tetr
athiafulvalene. The jump of the specific heat C at T-c and the exact f
orm of the specific-heat difference between C in the superconducting (
B = 0 T) and in the normal (B = 3.5 T) state can be well described by
BCS theory with strong coupling. We estimate an electron-phonon coupli
ng parameter lambda approximate to 1.1. From measurements of C in magn
etic fields we extract the upper critical field B-c2(T). Low-field dc-
magnetization measurements were used to determine the temperature depe
ndence of the lower critical field B-cl. From T-c down to similar to 3
K the characteristic suppression of B-cl(perpendicular to)(T) below t
he sensitivity limit is observed.