SPIN DYNAMICS AND SUSCEPTIBILITY APPROACHING THE NM-M TRANSITION IN KXKCL1-X

We report ESR measurements of KxKC1-x melts at 800 degrees C which for the first time have been studied over a wide composition range approa ching the nonmetal-metal transition (10(-4) less than or equal to x le ss than or equal to 10(-1)). The concentration has been varied precise ly by in situ Coulometric titration. The observed motional linewidth n arrowing gives evidence that fast electronic exchange processes prevai l in the nonmetallic melts. The spin susceptibility exhibits strong de viations from a simple Curie limit and its magnitude strongly indicate s that only a small fraction of excess electrons exists in paramagneti c states. Both the spin dynamics and the spin susceptibility show clea t changes near x = 0.05 indicative of the onset of a Mott-Anderson tra nsition. Over the whole nonmetallic regime the ratio of spin susceptib ility and electronic conductivity is found to be constant.