An Nmr Analysis Of Magnetic Correlations And Dimensionality In Organic Conductors

We present an analysis of experimental NMR data for a class of quasi one-dimensional (1D) organic conductors, the Bechgaard salts and their sulfur analogs. The temperature dependence of the nuclear relaxation, T 1 −1 , of the sulfur series (TMTTF) 2 X supports the existence of 1D antiferromagnetic fluctuations over a wide range of temperatures. Depending on the relative strength of the coupling to the lattice and on the interchain exchange coupling, these correlations evolve towards either a spin-Peierls or a spin density wave phase. We show that the analysis naturally extrapolates to the (TMTSF) 2 X family. The stabilization of the insulating magnetic phase at low magnetic field is apparently provided by the antiferromagnetic interchain exchange coupling, just as it is in the sulfur series. This provides a unique T-P phase diagram for both systems where the interplay between 1D correlation effects and interchain exchange coupling plays a crucial role.