RF Absorption by Submicron Metallic Particles

A comprehensive treatment is presented of the individual and collective RF absorbing properties of small, dilutely distributed metallic particles, under the conditions that the particles be Rayleigh scatterers having at least one submicron dimension. The particles are assumed spheroidal in shape of solid metal, and metal-layered with a non conducting, RF transparent core. The internal electric field and hence the electric moment of an RF irradiated particle is derived from the perturbation solution to the Greens theorem integral equation depicting the depolarizing effect of the induced surface charged and the power dissipation due to the volume current. The resultant internal field is thus the depolarized incident field within a skin-depth attenuation distance from the particle surface. The depolarizing factor derives naturally from the integral formulation, as the internal solid angle subtended by the surface normal component of the incident electric field. The efficiency of absorbers is then characterized by their depolarizing factors, conductivities, and A.C. permeabilities for ferromagnetic materials.