Spin density wave in the strongly dimerized quasi-one-dimensional organic conductor (DMET-TTF) 2 AuBr 2

At ambient pressure, studies of resistivity, magnetic susceptibility, and carbon-13 nuclear magnetic resonance (NMR) were conducted on the quasi-one-dimensional organic conductor ${(\text{DMET-}\mathrm{TTF})}_{2}{\mathrm{AuBr}}_{2}$. Resistivity measurements showed a broad minimum at approximately 160 K, and the insulator behavior below this temperature and magnetic susceptibility results revealed a dip structure at 22 K. At the same temperature, a sharp peak in the temperature dependence of ${T}_{1}^{\ensuremath{-}1}$ associated with the antiferromagnetic (AFM). transition was found, along with drastic splitting of the NMR spectra, indicating a commensurate AFM structure. The amplitude of the magnetic moments was determined to be $0.06{\ensuremath{\mu}}_{B}$/molecule from the hyperfine coupling constant tensor and the angular dependence of the internal field in the AFM phase. The small magnetic moment signifies the AFM nesting type, i.e., commensurate spin density wave. An antiferromagnetic ordering of $(\ensuremath{\uparrow}\ensuremath{\uparrow}\ensuremath{\downarrow}\ensuremath{\downarrow})$ along the one-dimensional chain is expected from the $2{k}_{\mathrm{F}}$ instability. This behavior can be explained by the strong dimerization of the one-dimensional DMET-TTF chain.