ABSTRACT
Usually, the energy relaxation of metallic samples is explained by the Elliott mechanism [77],
(37)
where Ag is the deviation of the g-factor from the free-electron value, and Ag is related to the strength of the spin-orbit coupling. Spin-orbit coupling probably plays a strong role in the relaxation of fluoride GICs (PF5, GeF4, AsF5, SbF5, and IF5). Since the spin-orbit coupling in CJF samples is weak, because of the low atomic masses of both fluorine and carbon, this mechanism cannot account for observed relaxation (g = 2.0025, so that Ag = 0.0002 and 7\ = 4 X 10~8t*) or scattering at the boundaries of the fluorine islands. The additional scattering is attributed to a small amount of magnetic impurity scattering [69]. The increase in 7\ with increasing fluorine concentration is attributed to the higher carrier mobility in the less concentrated fluorine-GICs. Because of the higher diffusion constant in CXF fibers with lower [F] concentration, electrons diffuse more rap idly to the magnetic impurities, where they are relaxed, thus leading to a shorter value for Tx in the less concentrated fibers. In summary, ESR measurements show that some properties are only weakly dependent on [F] concentrations as the Q.F system undergoes a metal-insulator transition, but other properties (such as the skin depth and the concentration of localized spins) are very sensitive to [F],
While electrical transport measurements have been carried out on a variety of fluorine GICs, thermal transport and optical studies have been made on only a few fluorine GICs. In this section the results of the various transport and optical measurements are summarized. Comparisons are also made with the correspond ing behavior of other acceptor GICs and with CJF compounds.
