The energy landscape of the magnetic system determines both the resultant magnetic structure and magnetic excitations. This is clearly demonstrated for the cubic B20-type compounds with the Dzyaloshinskii-Moriya (DM) interaction. The competition between the ferromagnetic exchanged interaction and antisymmetric DM interaction leads to the appearance of the homochiral helical magnetic structure. The spin-waves dispersion in case of the fully polarized helimagnet with the DM interaction is shifted for the helix wavevector.
The small-angle neutron scattering is used to measure the spin-wave stiffness in the field-polarized state of Dzyaloshinskii-Moriya helimagnet Cu2OSeO3, which is ordered below TC = 58 K. The scattering map in the full-polarized state (i.e. above ) demonstrates two overlapped circles centred at the Bragg angles.
The spin wave stiffness was measured at different temperatures and magnetic fields. The temperature dependence of the spin-wave stiffness decreases slowly with temperature showing no softening close to the critical temperature.