A fluctuation phase with spin chirality was detected in neutron scattering experiments during the phase transition in the chiral ferromagnet MnSi. This work shows that features of the fluctuation phase, such as a diffuse neutron scattering ring characterized by stochastic orientations of directed wave vectors, as well as the temperature dependences of the scattering propagation vector and the neutron polarization parameter, are explained by Berry degeneracy manifested in MnSi. Taking Berry degeneracy into account makes it possible to describe the observed jump in neutron scattering at the Curie point and the formation of diffuse scattering rings. In the region of spin short-range order, chiral topological charges acquire a preferred orientation due to Berry degeneracy. Their temperature dependence, described by the triple spin correlator, correlates with the temperature dependence of the neutron polarization parameters. When the exchange interaction changes with temperature beyond the regime of Berry degeneracy, the neutron beam becomes depolarized and spin chirality disappears.
Повзнер et al. (Mon,) studied this question.