DIPOLAR INTERACTION AND MAGNETIC ORDERING IN GRANULAR METALLIC MATERIALS

The coupling between magnetic clusters in granular metals is investigated assuming a classical dipolar interaction to couple the clusters. It is shown that in general the dipolar interaction energy is well described by replacing the clusters by an effective magnetic moment located at the center of mass of the cluster. The magnetization and reduced magnetoresistance of these systems are described as a function of an external magnetic field for a variety of cluster distributions. An experimental design that yields a system with high reduced magnetoresistance is suggested.