Low-dimensional magnetic behaviour of new radical-ion salts: (BEDT-TTF)2[AuIII(i-mnt)2] and (BEDT-TTF)2[BiBr4]

Electrical and magnetic properties of two new radicalion salts of BEDT-TTF (BEDT-TTF is bis(ethylenedithio)-tetrathiafulvalene) are reported. (BEDT-TTF)2[AuIII(i-mnt)2] (i-mnt is 1,1-dithio-2,2-dicyano-ethylene) is a semiconductor, σr.t. = 2.0 × 10−1−5.5 × 10−2 S cm−1 with a temperature dependent activation energy (0.14–19 eV). The powder magnetic susceptibility (10–300 K) has been fitted according to a uniform antiferromagnetic (S = 1/2) Heisenberg model by using the experimental g value of 2.0067 and a magnetic exchange constant J/kB of −110 K. (BEDT-TTF)2 [BiBr4] shows similar electrical and magnetic behaviour with σr.t. = 5 × 10−2 S cm−1 on a powdered sample and J/kB = − 79 K. At low temperature impurities are responsible for the Curie-like behaviour.