Hall Effect and Asymmetric Scattering in Pure Iron and Dilute Fe–Co at 4.2 K

Abstract

Hall effect and transverse magnetoresistance have been measured in fields up to 7 T (70 kG) in polycrystals. The Hall data for two samples of pure iron (ρ300/ρ4.2 = 1991 and 507 in small longitudinal fields) and for alloys with 0.25%, 0.50%, 0.92% Co fall roughly on the same Kohler curve as the iron data of Dheer if the resistivity in small longitudinal fields is used to construct the Kohler diagram. This curve is curved downwards at ωcτ ≈ 1, indicating the presence of more than two bands. For pure iron, extrapolation of the tangent of Hall angle to the high-field limit gives tanφH = (−2.2±0.5) × 10−2; a finite asymptotic value is predicted for a compensated magnetic metal, on the basis of asymmetric scattering. Extrapolation to the low-field limit for Fe–Co gives tanφH = (+1.4±0.2) × 10−2; a finite value is also predicted from asymmetric scattering. Contribution to Hall voltage from the nonclassical Kohn-Luttinger mechanism reaches 15% for the 0.92% Co sample, and must be subtracted from data.