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 similar to 0 to similar to 50 and from similar to 120 to similar 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.