Hall Effect and Magnetoresistance in Pure Iron, Lead, Fe-Co, and Fe-Cr Dilute Alloys

Abstract

Hall effect and transverse and longitudinal magnetoresistances have been measured in polycrystals at 4.2 K and below, in the fields up to 7 T. For pure iron ($\frac{{\ensuremath{\rho}}_{300}}{{\ensuremath{\rho}}_{4.2}}=523 \mathrm{and} 1993$), extrapolation of the Hall angle ${\ensuremath{\varphi}}_{H}$ to the high-field limit gives a nonzero value $tan{\ensuremath{\varphi}}_{H}=(\ensuremath{-}2.2\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ in agreement with our theory of asymmetric scattering in compensated metals. A nonzero high field, $tan{\ensuremath{\varphi}}_{H}=2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$, is also found for pure lead ($\frac{{\ensuremath{\rho}}_{300}}{{\ensuremath{\rho}}_{1.5}}=24300$) at 1.5 K; this and the nonlinear variation of the Hall resistivity might come from asymmetric scattering by traces of iron impurities known to be present. The Hall-resistivity data for pure iron, dilute Fe-Co, and the iron whiskers of Dheer fall roughly on the same Kohler curve which does not go through the origin. Extrapolation to the low-field limit for Fe-Co gives a nonzero value, $tan{\ensuremath{\varphi}}_{H}=(1.4\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$, in agreement with asymmetric scattering theory. Kohler's rule holds very well for the transverse magnetoresistance and the Hall resistivity of the Fe-Co alone. It fails completely for the Hall resistivity of Fe-Cr, which seems dominated by the nonclassical "side-jump" mechanism and not by asymmetric scattering. The value of the side-jump $\ensuremath{\Delta}y$ for Cr impurities in iron at 4 K is eight times as large as the usual value for scatterers in iron at 300 K.