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

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 ($\frac{{\rho }_{300}}{{\rho }_{4.2}}=523\mathrm{} \mathrm{and} 1993$), extrapolation of the Hall angle ${\phi }_H$ to the high-field limit gives a nonzero value $tan{\phi }_H=(-2.2\mathrm{}\pm 0.5)\times {10}^{-2\mathrm{}}$ in agreement with our theory of asymmetric scattering in compensated metals. A nonzero high field, $tan{\phi }_H=2\mathrm{}\times {10}^{-2\mathrm{}}$, is also found for pure lead ($\frac{{\rho }_{300}}{{\rho }_{1.5}}=24\mathrm{}300$) 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, $tan{\phi }_H=(1.4\mathrm{}\pm 0.2)\times {10}^{-2}$, 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 $\Delta y$ for Cr impurities in iron at 4 K is eight times as large as the usual value for scatterers in iron at 300 K.