Spiral magnetic correlation in cubic MnSi

Abstract

MnSi is a cubic ferromagnet with a long-wavelength spiral below its Curie temperature at 29 K. Recent theoretical and experimental studies have shown that this spiral is only right handed because of the lack of a center of symmetry in the Mn atomic arrangement. We have carried out elastic and inelastic neutron scattering experiments on a MnSi single crystal with the use of a neutron polarized-beam technique. A characteristic polarization dependence was observed in the magnetic Bragg reflections of the spiral phase, as well as the spin-wave excitations and the critical scattering near ${T}_{c}$. This polarization dependence persists into the ferromagnetic phase under a magnetic field and also at temperatures as high as 150 K.