The magnetophonon effect

This article is a review of the magnetophonon effect, covering its origins, uses and the information which derives from it. The magnetophonon effect arises due to resonant phonon emission or absorption by free charge carriers in a solid in a high magnetic field. The most usual example of this is when longitudinal optic (L.O.) phonons are absorbed by electrons or holes in a semiconductor, causing resonant transitions between Landau levels at magnetic fields given by the resonance condition B = (1/N)m¹ω_L.O./e, where ω_L.O. is the optic phonon frequency, and m¹ is the effective mass of the carriers in question. These resonant transitions cause resonances in a wide variety of different transport parameters, such as resistivity, Hall and Seebeck coefficients. The article reviews the observation of normal magnetophonon resonances in a wide variety of semiconducting and semi-metallic materials, including alloys, p-type materials and semiconductor heterostructures. A section is devoted to the hot-electron magnetophonon effect, which results from resonant electron cooling, and gives information on the electron energy loss mechanisms. This review was completed in December 1984.