Abstract

Helimagnetic order is a spatially periodic magnetic texture where the magnetization revolves around a fixed axis forming a helix. It is stabilized by the Dzyaloshinskii-Moriya interaction where the competition with the symmetric exchange interaction determines the wavelength of the helix. Here, we discuss the influence of spin-transfer torques on this texture arising from a spin-polarized current flowing along the helix axis. As the spin-current couples to the Goldstone mode of helimagnetic order associated with the spontaneous translational symmetry breaking, it induces a continuous rotation of the helix around its axis. More interestingly, the spin current also changes the wavelength of the helix. This latter effect cannot be obtained by a local stability analysis as it corresponds to a global instability of the helimagnetic order. We present analytical arguments describing this effect quantitatively, that are verified by numerical micromagnetic simulations.