Damped-wave size effect. I. Determination of carrier mobilities in Bismuth

A size effect (damped-wave size effect) resulting from the interaction of heavily damped electromagnetic waves in a conducting material subject to a static magnetic field is considered, and it is shown that, for a particular geometry, a maximum of the resistive power dissipation occurs at a fixed ratio of skin depth to sample thickness. This phenomenon allows a direct measurement of skin depth and may be used to study relaxation times. The geometry considered is that of a thin flat plate enclosed in a matching solenoid, which generates plane waves of opposite polarity at the opposite faces; the skin depth is varied by applying a magnetic field normal to the sample face. The characteristics of the phenomenon are analyzed and its utility as a general technique for the measurement of transport properties is investigated. The theory prescribes appropriate conditions for the observation of bulk effects in conductors in this geometry. The technique is applied to determine mobilities in bismuth, a semimetal with highly anisotropic Fermi surfaces. The relaxation times appear to be comparatively isotropic and to exhibit a single form of temperature dependence, obeying a T-2 law over much of the range from 4.2 to 77°K.