Sergey V. Barabash[1], David J. Bergman[1,2], and D. Stroud[1], [1] Department of Physics, The Ohio State University, Columbus, Ohio 43210; [2] School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Israel

Scaling theory, duality symmetry, and numerical simulations of a random network model are used to study the magnetoresistance of a metal/insulator/perfect conductor composite with a disordered columnar microstructure. The phase diagram is found to have a critical line which separates regions of saturating and nonsaturating magnetoresistance. The percolation problem which describes this line is a generalization of anisotropic percolation. We locate the percolation threshold and determine that t = s = 1.30 +/- 0.02 and that nu = 4/3 +/- 0.02, which are the same values as in two-constituent 2D isotropic percolation. We also determine the exponents which characterize the critical dependence on magnetic field and confirm numerically that nu is independent of anisotropy. We propose and test a complete scaling description of the magnetoresistance in the vicinity of the critical line.