RESISTANCE SCALING IN MEDIA WITH FRACTAL-LIKE STRUCTURE IN THE VICINITY OF A METAL-INSULATOR-TRANSITION

Scaling relation between residual R0 and temperature-dependent R1 parts of the sample electrical resistance in the vicinity of a metal-insulator transition can be a guide in examining the structure of the material. Three possible values of the exponent ν in the relation R1 ∝ (R0)ν are discussed. ν = 1 is typical for a random mixture of metallic and insulating domains, ν = 0 for granular metals. A special case ν = 0.75 which has been observed recently corresponds to a fractal structure of the insulating phase with the classical size effect governing the conductivity of the metallic channels. Experimental data on ZnSb and AlGe alloys are presented. © 1990.