Weak-field magnetoresistance in noncubic (111)-oriented epitaxial films of n-type PbTe

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Abstract
Measurements of the weak‐field magnetoresistance (WFMR) were carried out at 300 and 77 K on two (111)‐oriented n‐type PbTe epitaxial films, 4 and 10 μm thick. A recently developed single‐sample four‐measurement technique and a cubic‐trigonal‐hexagonal extension of the Seitz–Pearson–Suhl WFMR phenomenology were used to obtain and analyze the data. Significant deviations from the requirements of cubic symmetry were detected, the effect being larger in the thinner film and at the lower temperature. A WFMR coefficient ratio, which would have been unity for a cubic environment, ranged from 1.3 to 6.8. These noncubic results are tentatively ascribed to the effects of substrate‐induced strain on the films. The four WFMR coefficients were fitted to a simple trigonally distorted three‐parameter model of the PbTe conduction band. For reasons not yet identified, the fit was very good for the thinner film and quite poor for the other one.