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.
Categories: cond-mat.supr-con cond-mat.str-el