Possible Mott transition in (BEDT-TTF)2CsZn(SCN)4

The magnetic properties of a new organic conductor, (BEDT-TTF)2CsZn(SCN)4, have been investigated by 1H-NMR, EPR and SQUID measurements. The resistivity of the title compound exhibits a small temperature dependence down to about 50 K and an abrupt increase below 20 K. The spin susceptibility was almost temperature independent down to 20 K, and exhibits a Curie-Weiss behavior below that temperature. The 1H-NMR spin-lattice relaxation rate, T1−1, has a large temperature dependence with a broad minimum around 50 K. We discuss the electronic structure of the low-temperature insulating states of this system.