CHARGE TRANSFER-CONTROLLED PHASE-TRANSITION IN A MOLECULAR CONDUCTOR, (DME-DCNQI)(2)CU-DOPING EFFECT

Li+ doping in the Cu salt of deuterated DMe-DCNQI-d(7), has shown drastic effects on electrical and magnetic properties. Undoped (DMe-DCNQI-d(7))(2)Cu exhibits a first-order metal;insulator (M-I) transition at 80 K. A small amount of Li+-doping suppresses the M-I transition. The M-I-M (reentrant) transition, which is Similar to that in selectively deuterated (DMe-DCNQI)(2)Cu, appears in a narrow region of Li content x. The x-T phase diagram under ambient pressure well reproduces the P-T phase diagram of the (DMe-DCNQI)(2)Cu system. This doping effect is explained by the change in charge transfer amount from metal ions to DCNQI molecules. The effect of pressure or deuteration on the M-I transition in the DCNQI(2)Cu system is generally understood from this viewpoint.