TEMPERATURE-DEPENDENCE OF THE ELECTRONIC SPIN RELAXATION OF DCNQI SALTS

For the elucidation of the charge and spin dynamics of the radical ani on salts of DCNQI with metallic counterions we have performed cw- and pulsed ESR experiments (Delta B-pp, T-1e(-1) and T-2e(-1)) between 300 and 4 K at nine salts differing in counterions and sidegroups, respec tively. We can explain the relaxation rates by dipolar electron-electr on interaction and spin-orbit contribution. In the high temperature ra nge we have a gradual decrease in the number of charge carriers by int erband transitions without a slowing down of the mobility. With comple te localization of the electron spins (no mobile electrons anymore) ex change interaction governs the spectral density, becoming strongly tem perature dependent due to effective spin exchange J(eff)(T), explained by an extended REHAC-model, This effective spin exchange J(eff)(T) in cludes for the first time a contribution by the metallic counterions. For spin-orbit interaction we developed a model based on F. Adrian [1] not depending on the mixture of Bloch and spin states as given by Ell iott [2]. This is achieved by the inclusion of the electronic probabil ity on atoms with higher atomic numbers, modulated by phonons. This mo del explains the drastic changes in the ESR linewidth of different rad ical ion salts of DCNQI and allows inductively the prediction of the e lectronic properties of new radical ion systems of which just the mole cular and crystal structure is known.