Magnetoresistance in PbS, PbSe, and PbTe at 295°, 77.4°, and 4.2°K

Magnetoresistance measurements made on 14 single crystals of PbS, PbSe, and PbTe at 77.4°K conformed to the general phenomenological weak-field theory; i.e., the magnetoresistance was proportional to $H^2$, and varied sinusoidally with the angle between the sample current and magnetic field. Because of the extremely high mobilities in the samples at 4.2°K, weak-field theory was generally not applicable, and saturation effects and striking deviations from the sinusoidal behavior were observed at this temperature. The longitudinal magnetoresistance was generally larger (in some cases, 4 or 5 times larger) than the transverse at both 77.4° and 4.2°K. The results did not appear to be significantly different for $n$- and $p$-type material. The data generally favor a model with considerable mass anisotropy; in particular, the many-valley model having ellipsoids of revolution along the $〈111〉$ directions, with a ratio of longitudinal to transverse effective mass of between 4 and 6, seems most appropriate for PbTe.