High-Field Magnetotransport in a Percolating Medium

A discrete network model is used to discuss the critical behaviour of magnetotransport in a percolating medium in the presence of a magnetic field H of arbitrary strength. By applying a real-space renormalization group transformation, we find that there is strong magnetoresistance ρ( H ) near the percolation threshold. We also find that there are two fixed points: one at p = p c and H = 0, and another at p = p c and H = ∞ . The crossover between them is governed by a new, field-dependent length. In a percolating metal-insulator mixture, the resistivity ratio with and without a field ρ( H )/ρ(0) is predicted to saturate as p → p c at a value ∼ H 0.5 .