Relaxation study in percolating solids

Abstract

The strain-relaxation (creep) behavior of randomly cut metallic networks (of aluminum and copper) near the percolation threshold are studied here experimentally. A crossover from Kohlrausch-type stretched-exponential behavior, for time t less than a crossover time t_c, to a normal (exponential) relaxation behavior, for t>t_c, is observed. The crossover time (t_c) and the relaxation time are found to diverge as disorder approaches the percolation threshold. The value of the stretched-exponential exponent is compared with that expected theoretically from anomalous diffusion on fractals. Such crossover behavior for strain relaxation in percolating networks is compared with the magnetic-relaxation behavior of dilute Ising magnets in two and three dimensions, studied using Monte Carlo simulation techniques. These observations confirm a classical localization or anomalous-diffusion origin of the stretched-exponential relaxation behavior.