Hall Voltage and Magnetoresistance of Bi Measured by a Sum Frequency Method in a Belt Apparatus

An alternating magnetic field, 1.4 kG in amplitude at 5 Hz, was obtained in a belt type of high pressure apparatus by the use of conical pistons made of hardened high speed tool steel, permitting operation up to 50 kilobar. A frequency of 12 Hz was used for the current through the sample, and the Hall voltage was synchronously detected at 17 Hz. A signal yielding the coefficient of magnetoresistance was extracted at 22 Hz, using another lock-in amplifier. The Ohmic resistance may also be measured in the same experiment, and, by making certain assumptions, the variation of the carrier density and the hole and electron mobilities of a semimetal may be determined. Data for polycrystalline Bi at room temperature are given.