Heliconlike Wave Propagation in Powdered Semiconductors at Microwave Frequencies

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Abstract
Experiments on the propagation of 35-GHz microwaves in magnetically biased powdered narrow-gap semiconductors are described and their major features explained by a simple single-scattering theory derived in the paper. Attention is restricted to grains much smaller than the wavelength of the incident waves. The grains are idealized to spheres which are gyroelectric because of the applied dc magnetic field. The scattering and absorption properties of an isolated gyroelectric sphere are analyzed using an ad hoc assumption that, under a given normal-mode excitation, a gyroelectric sphere can be represented by an isotropic sphere described by the bulk permittivity associated with that excitation. This approach explains the main features of the data in terms of particle-size-dependent resonances and high-field size-independent absorption. Variations of resonance position and strength with powder grain size, size distribution, temperature, and carrier concentration are easily understood using the single-particle expressions. Low-temperature microwave transmission in InSb and InAs powders shows well-resolved Shubnikov-de Haas oscillations at field values in remarkably good agreement with theory.