Magnetic properties of DCNQI-Cu systems

Recent advances in the study of magnetic properties of a series of molecular conductors, Cu salts of DCNQIs, are presented. First, the antiferromagnetic order of Cu spins in the insulating phases below about 10 K is found to be accompanied by weak ferromagnetism with the spontaneous moment perpendicular to the tetragonal c-axis. Second, our susceptibility study of the metal-insulator-metal (M-I-M) reentrant system, (DMe-DCNQI-α,α′-d2)2Cu, has lead to the absence of many-body enhancement of the susceptibility in the low temperature metallic phase. Finally, (DI-DCNQI)2Cu is found to exhibit considerably enhanced and temperature dependent susceptibility, suggesting the effect of spin fluctuation in the metallic state.