13C NMR measurements of the high-magnetic-field, low-temperature phases of (TMTTF)2PF6

We report NMR spectroscopy of C-13-labeled TMTTF molecules in high-magnetic fields that established the field-temperature phase diagram for (TMTTF)(2)PF6. The dimerized spin-Peierls (D) ground state is driven to an incommensurate (I) phase for fields B > B-c = 19.1 +/- 0.1 T. In the I phase, the staggered component of the magnetization is much larger for (TMTTF)(2)PF6 than it is for CuGeO3. On approaching the transition to the D phase from higher temperatures, we observe an unusual broadening of the NMR spectrum which is probably from extrinsic sources and related to pinning of solitonlike excitations in individual chains.