A recently developed self-consistent effective-medium approximation, for composites with a columnar microstructure, is applied to such a three-constituent mixture of isotropic normal conductor, perfect insulator, and perfect conductor, where a strong magnetic field B is present in the plane perpendicular to the columnar axis. When the insulating and perfectly conducting constituents do not percolate in that plane, the microstructure-induced in-plane magnetoresistance is found to saturate for large B, if the volume fraction of the perfect conductor ps is greater than that of the perfect insulator pI. By contrast, if ps<pI, that magnetoresistance keeps increasing as B2 without ever saturating. This abrupt change in the macroscopic response, which occurs when ps=pI, is a critical point, with the associated critical exponents and scaling behavior that are characteristic of such points. The physical reasons for the singular behavior of the macroscopic response are discussed. A different type of percolation process is apparently involved in this phenomenon.
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 1 Dec 2000|