Uniaxial polarization analysis of bulk ferromagnets: theory and first experimental results

Based on Brown’s static equations of micromagnetics, the uniaxial polarization
of the scattered neutron beam of a bulk magnetic material is computed. The
approach considers a Hamiltonian that takes into account the isotropic
exchange interaction, the antisymmetric Dzyaloshinskii–Moriya interaction,
magnetic anisotropy, the dipole–dipole interaction, as well as the effect of an
applied magnetic field. In the high-field limit, the solutions for the magnetization
Fourier components are used to obtain closed-form results for the spinpolarized SANS (small-angle neutron scattering) cross sections and the ensuing
polarization. The theoretical expressions are compared with experimental data
on a soft magnetic nanocrystalline alloy. The micromagnetic SANS theory
provides a general framework for polarized real-space neutron methods, and it
may open up a new avenue for magnetic neutron data analysis on magnetic
microstructures.