The frequency dependence and magnitude of the far-infrared absorption of a small-metal-particle composite material has been measured over the range of 4-100 ${\mathrm{cm}}^{-1\mathrm{}}$. The composite samples consisted of spherical metal particles, with radii varying from 100-1000 Å, randomly dispersed in an insulating host. In some samples, a nonlinear dependence of the absorption on the metal-particle concentration was observed, indicating that interparticle interactions can play an important role. It is shown that the magnitude of the absorption cannot be explained by classical electromagnetic theory.

• Received 23 December 1980

DOI:https://doi.org/10.1103/PhysRevB.24.777