Abstract
Results of polarized neutron small angle scattering in MnSi, a cubic itinerant magnet, near Tc=28.8 K are presented and analyzed. The diffuse scattering intensity looks like half-moons oriented along the incident neutron polarization. The sum of the intensities for two opposite polarizations form an anisotropic ring with weak spots, which below Tc transform into the Bragg peaks originating from the helical structure. These results are in semiquantitative agreement with the mean-field calculations based on the Bak-Jensen model that takes into account the hierarchy of the interactions: the exchange interaction, the isotropic Dzyaloshinskii-Moriya (DM) interaction and the weak anisotropic exchange (AE) interaction. The DM interaction is responsible for the scattering intensity concentrated in the half-moons. The AE interaction provides the anisotropy so that the correlation length diverges along [111] only.
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