Modulation of skyrmion helicity by competition between Dzyaloshinskii-Moriya interaction and magnetic frustration

Helicity, one of the degrees of freedom for skyrmions, describing the direction of spin rotation in skyrmions, is of fundamental importance for skyrmion-based potential applications. However, continuously modulating the helicity is challenging. Here, we propose an effective method to control the skyrmion helicity by means of the competition between Dzyaloshinskii-Moriya interaction and exchange frustration in inversion-symmetry-broken frustrated magnets. In the prototypical case of Janus NiClBr, we found a nanometer-sized skyrmion with uniform unconventional helicity of 139^∘. Moreover, a spin texture phase diagram as a function of strain and out-of-plane magnetic field was illustrated and, most importantly, an unexpected linear change in the helicity from ~0^∘ to ~50^∘ and from ~120^∘ to ~180^∘ was found in the skyrmion lattice region. As such, the skyrmion Hall effect of Janus NiClBr can be reduced under external field for a critical value of the helicity. These results not only give a feasible method to effectively modulating the skyrmion helicity, but also provide an ideal platform for further investigations on skyrmion helicity-related phenomena.