Magnetic Field Dependence of Chiral Fluctuations in {{MnSi}}

Polarized neutrons were used to determine the antisymmetric part of the magnetic dynamical susceptibility w\dh{}Q; o\TH{} in the weak ferromagnet MnSi. We find that above the Curie temperature Tc the spin fluctuations are incommensurate with the chemical lattice and that w\dh{}Q; o\TH{} depends on the polarization of the incident neutron beam Pi like \dh{}Q Á Pi\TH{} where Q is the scattering vector. Because the crystal structure of MnSi is non-centrosymmetric we interpret these results in terms of the antisymmetric Dzyaloshinskii\textendash{}Moriya interaction which yields a non-zero contribution to the antisymmetric part of w\dh{}Q; o\TH{}: Additional measurements performed below Tc show that in zero field the spin excitations in MnSi have also in the ordered phase a chirality. With increasing external magnetic field B; the magnetic excitations evolve from helical to ferromagnetic-like. In the field-induced phase where the magnetic moments are aligned, magnon annihilation and creation are observed for 7Pi==B; respectively.     «

Polarized neutrons were used to determine the antisymmetric part of the magnetic dynamical susceptibility w\dh{}Q; o\TH{} in the weak ferromagnet MnSi. We find that above the Curie temperature Tc the spin fluctuations are incommensurate with the chemical lattice and that w\dh{}Q; o\TH{} depends on the polarization of the incident neutron beam Pi like \dh{}Q Á Pi\TH{} where Q is the scattering vector. Because the crystal structure of MnSi is non-centrosymmetric we interpret these results in te...     »