Role of interchain hopping on electron spin relaxation in quasi-one-dimensional case

Theories cannot actually predict the value and the T-dependence of the electronic spin resonance linewidth of organic conductors. To compensate this difficulty, most of the experiments have been carried out on families of compounds. In order to reduce the number of parameters, we have modified on the same compound (TTF-TCNQ) the interchain coupling by introducing chain breakings. We observed an unusual decrease of the linewidth when the degree of disorder increases. A model of spins localized on metallic segments, and where the spins are reversed by the interchain jumps, described this variation of the linewidth. The parameters found in this model are in agreement with those determined by conductivity measurements. However, in order to take into account the whole disorder range, the dipolar interaction between localized spins should not be neglected : this term is dominant at low temperatures and for the highest disordered compounds. One can generalize these results which are demonstrated on the case of TTF-TCNQ to the other organic conductors.