Electrical and structural properties of κ-type organic conductor

Abstract

The electrical resistivities of organic metals with κ-type molecular arrangements were examined. Superconducting transition temperature (Tc) of alloy system κ-[(ET)1-x(STF)x]2 Cu[N(CN)2]Br (ET=BEDT-TTF, STF=BEDT-DSeDTF) is rapidly depressed with increase of the doping amount of the asymmetric π-donor STF. Tc becomes lower than 1.6 K at x>0.25 but the system retains metallic state at least up to x=0.6. The characteristic resistivity maximum is smeared with increasing x. The metal-insulator transition of κ-ET2Au(CN)2 at 70 K is suppressed by applying “soft pressure” of about 550 bar. The electrical properties and the crystal stuctures of κ-MT2Cu[N (CN)2]X (MT=BMDT-TTF, X=Cl, Br) were also examined. The crystal of κ-MT2Cu[N(CN)2]X belongs to monoclinic system with space group Cc. The structure of anion sheet closely resembles that of κ-MT2Cu[N(CN)2]X. The electrical resistivity decreases monotonously down to 2 K.