Microwave Magnetic Dipole Interaction in Small InSb Spheres: Induced Cyclotron-Resonance-Like Absorption in the Rayleigh Limit

We report a new type of microwave resonant absorption observed in small spheres of $n$-type InSb at 35 GHz and 77 °K. The resonance is excited by the time-varying magnetic field, and occurs at approximately three times the cyclotron-resonance frequency. Although an exact theory for the phenomenon does not exist, the effect is examined in terms of an approximate analysis. It is formally identified as the magnetic dipole mode of oscillation of a bounded free-carrier plasma.