The behavior of the proton spin-lattice relaxation rate T-1 1 in the organic superconductors (BEDT-TTF)4Hg2.78Cl8 (I) and (BEDT-TTF)4Hg2.89Br8 (II) is studied over the ranges of temperature 4.5≤T≤300 K and resonance frequency 33≤v≤360 MHz. At T<150 K we have found a strong frequency dependence of T-1 1 in II with a maximum between 90 and 200 MHz. This unusual frequency dependence can be explained by cross-relaxation via quadrupolar Br nuclei. The temperature dependence of T-1 1 in both I and II at low temperatures is found to be non-Korringa.
ASJC Scopus subject areas
- Condensed Matter Physics