Estimating the Enantiomorphic Excess in Polycrystalline Metal Samples with a B20-Type Structure

Abstract

The degree of enantiomorphic excess (average chirality 〈Γ〉)in bulk polycrystalline Fe_1–xCo_xSi samples with a cobalt concentration of x = 0.10, 0.15, 0.20, 0.25, 0.30, and 0.50 is studied. Polycrystals are synthesized by melting the initial high-purity components. Surface examination of the samples showed that they are composed of acicular coaxially oriented crystallites with an average volume of ~2 mm³. The magnetic chirality γ, which is directly related to the crystallographic chirality Γ as γ =–Γ, is measured using small-angle polarized neutron diffraction. It is established that the average chirality of polycrystals 〈γ〉 is independent of the Co concentration within the statistical precision of the number of crystallites in the samples used in the experiment. The chirality of individual polycrystallites is distinct from zero and sometimes reaches 10–20%, being determined by the total number of crystallites in a sample (~100). The measurement error of the average chirality 〈γ〉 is determined by neutron scattering statistics and does not exceed 1%.