Transverse magnetoresistance and its temperature dependence for high-purity polycrystalline aluminum

Abstract

Polycrystalline-aluminum-tape samples of 0.3×6 mm2 cross section have been used to measure the zero-field resistivity and the transverse magnetoresistance up to 3.9 T. The main purpose of our investigation was to study the temperature and purity dependence of the magnetoresistance. Measurements were taken continuously in the temperature range 4.2–32 K for six samples differing in purity. The bulk residual resistivity ratio rb chosen as a measure of purity varied from 2400 to 30 000. In the high-field region the magnetoresistance increases with temperature up to a maximum at about 20 K. The maximum itself increases with purity and leads for the purest sample to a resistivity increase by a factor of 6.8 (B=3.9 T, T=17 K). The unusual temperature behavior of the resistivity with and without magnetic field, which means a violation of the Kohler and Matthiessen rule, is discussed and explained regarding the anisotropic electron-phonon scattering. Following the theoretical concept of Kagan a qualitative agreement could be obtained. Measurements of the Hall effect on a rb=24 500 sample were performed to support the interpretation of the magnetoresistance results.