Antiferromagnetic and structural instabilities in tetramethyltetrathiafulvalene thiocyanate [(TMTTF)S2CN]

Abstract

The low-temperature phase transitions of tetramethyltetrathiafulvalene thiocyanate are described through magnetic and structural studies. A first transition, which occurs at 160 K, drives the electron gas into a localized state and is shown to be associated with a superstructure formation. Then, the condensation of an unexpected antiferromagnetic ground state is observed around 7 K. We suggest that this striking behavior is related to the peculiar wave vector ($a^{*}, \frac{1}{2}{b}^{*}, \frac{1}{2}{c}^{*}$) of the 160-K superstructure.