Molecular motion and high-temperature paramagnetic phase in κ-(BEDT-TTF)2Cu [N(CN)2]Cl

Abstract

The organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl has been studied for the examination of the conducting mechanism of the semiconducting behavior at high temperatures by 13C-NMR spectroscopy. We found that the temperature dependence of the linewidths and the spin-spin relaxation rate T2-1 showed a peak structure characterized by the hyperfine coupling constant in this region, suggesting a connection between ethylene motion and conducting electrons similar to that observed in κ-(BEDT-TTF)2Cu(NCS)2. Although κ-(BEDT-TTF)2Cu[N(CN)2]Cl salt was thought to be an insulator at high temperature, our findings suggest that all κ-type salts at high temperatures could be in the same phase where the scattering caused by ethylene motion is added to bad metal.