Proton NMR linewidth and relaxation-rate study of an organic conductor with an antiferromagnetic ground state

The inhomogeneous broadening of the proton NMR line which occurs at the Néel temperature of bis(tetramethyltetrathiafulvalene) thiocyanate [${\mathrm{}\left(\mathrm{TMTTF}\right)\mathrm{}}_2$ SCN] is used to determine the magnitude of the sublattice magnetization in the antiferromagnetic state. A value of order 0.1${\mathrm{\mu }}_{\mathit{B}}$ is obtained, comparable to those for other salts in the family. The spin-lattice relaxation rate shows a relatively strong, asymmetric lambda anomaly at the transition. Two features in $T_1\mathrm{}\left(T\right)\mathrm{}$ at higher temperature are interpreted in terms of rotation of inequivalent methyl groups.