DIPOLAR INTERACTION AND MAGNETIC-ORDERING IN GRANULAR METALLIC MATERIALS

The coupling between magnetic clusters in granular metals is investiga ted assuming a classical dipolar interaction to couple the clusters. I t is shown that in general the dipolar interaction energy is well desc ribed by replacing the clusters by an effective magnetic moment locate d at the center of mass of the cluster. The magnetization and reduced magneto resistance of these systems are described as a function of an external magnetic field for a variety of cluster distributions. An exp erimental design that yields a system with high reduced magnetoresista nce is suggested.