Superconducting Fluctuations and the Reduced Dimensionality of the Organic Superconductor $\kappa$- (BEDT-TTF)$_{2}$Cu(NCS)$_{2}$ as Observed through Measurements of the de Haas-van Alphen Effect

We report measurements of the de Haas-van Alphen (DHVA) effect and AC susceptibility in the layered organic superconductor $\kappa$-(BEDT-TTF)$_{2}$Cu(NCS)$_{2}$. The amplitude of the DHVA oscillations is attenuated over a wide field range above the irreversibility line, B_irr(B), below which a rigid flux lattice is formed. Thus the DHVA effect provides a unique probe of the superconducting fluctuations at high fields in this material. We compare our measurements with other determinations of the superconducting phase diagram of $\kappa$-(BEDT-TTF)$_{2}$Cu(NCS)$_{2}$.