Periodically modulated skyrmion strings in Cu2OSeO3

Magnetic skyrmions are vortex-like spin textures, which are usually treated as two-dimensional objects. In their lattice state, they form well-ordered, hexagonal structures, which have been studied in great detail. To obtain a three-dimensional (3D) skyrmion crystal, these planes can be envisaged to be stacked up forming skyrmion strings in the third dimension. Here, we report the observation of a 3D skyrmion phase in Cu2OSeO3 by carrying out reciprocal space mapping in resonant elastic x-ray scattering. We observe regions in the magnetic field-cooling phase diagram in which the skyrmion phase apparently coexists with the conical phase. However, such a coexistence is forbidden due to symmetry arguments. Instead, the skyrmion strings themselves are periodically modulated along their axes, as confirmed by micromagnetic simulations. The periodic modulation is in fact a necessary consequence of the evolution of the skyrmion phase out of the conical state and should therefore be a universal property of skyrmion strings in chiral helimagnets.

Automated summary

Magnetic skyrmions are vortex-like spin textures treated as two-dimensional objects, but researchers have observed a three-dimensional skyrmion phase in Cu2OSeO3 using resonant elastic x-ray scattering. This 3D phase exhibits regions where the skyrmion phase coexists with the conical phase, which was previously thought to be forbidden due to symmetry arguments. However, the study shows that the skyrmion strings themselves undergo periodic modulation along their axes during the transition from the conical state, indicating a universal property of skyrmion strings in chiral helimagnets.