Metal-insulator transition in nanocomposites of glass and RuO2

We report on studies of interplay between percolation and quantum localizat ion in mixtures consisting of glass grains and RuO2 metal particles of aver age diameters 550 and 10 nm, respectively. A weak temperature dependence of conductivity sigma(T) = a + bT(alpha), where alpha congruent to 0.20, is f ound in the temperature region 0.04 < T < 1 K. Similarly, an anomalously sm all magnitude of magnetoconductivity is observed in the studied magnetic fi eld range up to 5 T. These observations demonstrate that percolation nature of electron transport leads to a significant modification of quantum corre ctions to conductivity at the localization boundary. The conductivity at cr iticality obeys a dynamic scaling equation with the conductivity exponent m u = 1.65 as expected for one-electron Anderson localization.