Plasma Resonance in Crystals: Observations and Theory

Observations are reported of an electron plasma resonance absorption line in a magnetic field in an $n$-type crystal of InSb at 9000 and 24 000 Mc/sec and at 4\ifmmode^\circ\else\textdegree\fi{} and 77\ifmmode^\circ\else\textdegree\fi{}K. The magnitude of the plasma frequency and its dependence on rf frequency and on the orientation of the figure axis of the specimen relative to the static magnetic field are in approximate agreement with the elementary theory of the plasma resonance developed previously by the authors. The line shape is discussed for experiments carried out under conditions of carrier modulation and magnetic field modulation. A theoretical discussion is given of the effects of specimen shape and of the possibility of detection of minority carrier cyclotron resonance in the presence of a majority carrier plasma. Eddy current effects are discussed, with reference to the possibility of the detection of cyclotron resonance in metals and semimetals.