The influence of sample shape on microwave magnetoplasma and heliconlike resonances in n-type InSb

Abstract

Magnetoplasma and heliconlike dimensional resonances are investigated in small samples of n-type InSb interacting with 8-mm wave radiation at 77 K, in order to determine the influence of sample geometry on the interaction, particularly the shift of the resonance condition. Special attention is paid to the disk geometry because of its practical importance. The results are compared with mathematically tractable, but experimentally less practical, geometries: the sphere, the ellipsoid of revolution, and the infinite slab. It is found that, in analogy with ellipsoids, the magnetoplasma resonance in disk samples is determined by an empirical effective depolarizing factor, which is surprisingly close to the depolarizing factor of an ellipsoid of the same axial ratio as the disk. By using very thin disks, magnetoplasma resonance can be shifted to significantly lower magnetic fields than the resonance field observed in spheres. This is of importance for determining the lattice dielectric constant in materials containing a high concentration of carriers, for which magnetoplasma resonance in spheres occurs at inaccessibly high fields. We also observe a sequence of heliconlike dimensional resonances in disks. These resonances form a series of electric dipole and magnetic dipole excitations, as in the case of spheres. However, the resonance conditions for the disk samples are close to the Fabry-Perot resonances in an infinite plate.