Depolarization effects in arrays of spheres

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Abstract
The effect of aggregation upon depolarization fields was investigated in several geometric configurations of InSb spheres by means of the microwave magnetoplasma resonance. Microwave absorption by the arrays of spheres was measured while the dielectric constant of InSb was varied in situ by sweeping a magnetic field. The magnetic field at which magnetoplasma resonance occurs is explicitly dependent upon depolarization effects, so that values of the depolarizing factors could be determined for each of the configurations. These values were compared to those obtained from the available theories of dipole-dipole interactions. The results showed general qualitative agreement; however, the discrepancies in the quantitative values indicate that some of the basic assumptions underlying the theories should be reevaluated. In particular, our studies suggest that the point-dipole approximation, used in the theories addressed to the problem, is highly inadequate. Proximity effects must be incorporated in more realistic descriptions.