PULSED ESR OF CONDUCTING ALKALI-DCNQI SALTS - A GENERAL-ANALYSIS OF THE ELECTRONIC SPIN RELAXATION RATES

We have determined the temperature and angular dependence of the elect ronic spin relaxation rates 1/T1e and 1/T2e in the radical anion salts of M(2,5-DMe-DCNQI)2 with metallic counterions (M=Li, Na, K and Rb), originating from the dipolar interaction between the spins of the cond uction electrons (FS) and from contributions by spin orbit coupling (S OC). Taking into account the known crystal structures, the FS contribu tion could be determined quantitatively by (i) calculating the spin de nsity distribution on the DCNQI molecule, (ii) summing over all neighb oring molecules within two lattice constants, and (iii) introducing a 1D spectral density function for the electronic mobility. Using semicl assical relaxation theory for SOC interaction we introduced a new mode l for 1D systems based on the following considerations. Each 'out-of-c hain scattering event' of the conduction electrons leads to an angular -dependent relaxation contribution. This depends on the relative mutua l arrangement of the DCNQI molecules, i.e., the crystal structure, and possesses a spectral density resulting from a pulse-like interaction. The quantitative analysis of the experimental data gave spin diffusio n constants D for the four salts of 0.05-0.4 cm2 s-1, anisotropies sig ma(parallel-to)/sigma(perpendicular-to) of (3.8-6.5) X 10(3), and, by comparison of the conductivity data, additionally allowed the separati on between the activation energies of the charge carrier concentration (about 17 meV) and that of the 'effective mobility'.