Commensurability of the spin-density-wave state of (TMTSF)2PF6 observed by 13C-NMR

A spin-density-wave (SDW) for (TMTSF)(2)PF(6) has been reported to appear below T(SDW) (=/~12 K), with a subphase transition at T* (=/~4 K). To determine the structure of the subphase, we synthesized (TMTSF)(2)PF(6), in which one side of the central carbon bond in each TMTSF molecule was replaced by (13)C, and utilized this compound in (13)C nuclear magnetic resonance measurements. Below T(SDW), the spectrum became broad and T(1)(-1) decreased, in agreement with previous results. Below T*, fine structures emerged in the center of the spectrum and T(1)(-1) decreased exponentially. These phenomena were attributed to the emergence of commensurability at T*.