A theory of giant magnetoresistance in granular alloys was developed by considering the spin-dependent scattering within the magnetic granules and at their boundaries and the continuous distributions of granule sizes and directions of magnetization. The CPP formalism was recovered in the limit when the effective conductivities in the granules are much larger than the matrix conductivity. When this condition is not satisfied, the transport properties of the granular alloys derive from the crossover of the parallel and perpendicular current configurations.

• Received 26 May 1998

DOI:https://doi.org/10.1103/PhysRevB.59.8412