Magnetic and Electronic Phase Diagram and Superconductivity in the Organic Superconductors k-(BEDT-TTF)2X
Abstract
The magnetic susceptibility of the organic superconductors \kappa-(h8 or d8-ET)_{2}X, X = Cu(NCS)_{2} and Cu[N(CN)_{2}]Br has been studied. A metallic phase below T^{*} = 37 \sim 38 K for X = Cu[N(CN)_{2}]Br and 46 \sim 50 K for X = Cu(NCS)_{2} has an anisotropic temperature dependence of the susceptibility and the charge transport. Partial charge-density-wave or charge fluctuation is expected to coexist with the metallic phase instead of the large antiferromagnetic fluctuation above T^{*}. The phase diagram and the superconductivity of \kappa-(ET)_{2}X are discussed in connection with this phase.