The discovery of a new topological form of magnetic order in the family of cubic Dzyaloshinskii-Moriya helimagnets almost a decade ago has continued to attracted increasing scientific interest. This new magnetic state consists of a lattice of skyrmions, i.e., magnetic vortices characterized by a topological winding number. This implies that skyrmions represent topologically-protected magnetic particles with a mesoscale size typically of the order of 10-200 nm. Their topologically-protected nature makes them insensitive to atomic-scale defects and impurities and enables them to move independently from the underlying crystal structure. In particular, it has been shown that ultra-low current densities of 10⁶ A/m² allow moving skyrmions through a material via the spin-torque effect. Moving conventional spin-textures such as domain walls requires six orders of magnitude higher currents. Together with the ability to create and delete individual skyrmions via current pulses or polarized spin-currents these novel spin textures have unprecedented potential for low-power/high-density non-volatile racetrack memories and spintronics. Here we will summarize the fundamental ingredients that result in the formation of skyrmion lattices and their functionality that we have identified in an extensive study using small angle neutron scattering [1], neutron spectroscopy [2, 3] and resonant ultrasound spectroscopy (RUS) [4]. Notably, using RUS we uncover a new regime of previously theoretically predicted creep motion at even lower currents that suggests that skyrmions may be moved with currents lower than 10⁴ A/m² [5].

[1] D. M. Fobes, Yongkang Luo, N. Leon-Brito, E. D. Bauer, V. R. Fanelli, M. A. Taylor, L. M. Debeer-Schmitt, M. Janoschek, Appl. Phys. Lett. 110, 192409 (2017).

[2] M. Kugler, G. Brandl, R. Georgii, K. Seemann, M. Janoschek , J. Waizner, M. Garst, A. Rosch, C. Pfleiderer, and P. Böni, Phys. Rev. Lett. 115, 097203 (2015).

[3] D. M. Fobes, T. Weber, M. Kugler, J. Waizner, A. Bauer, R. W. Bewley, G. Ehlers, R. Georgii, C. Pfleiderer, P. Böni, M. Garst, and M. Janoschek, in preparation.

[4] Yongkang Luo, Shizeng Lin, D. M. Fobes, Zhiqi Liu, E. D. Bauer, J. B. Betts, A. Migliori, J. D. Thompson, M. Janoschek, and B. Maiorov, Accepted for publication in Phys. Rev. B, arXiv:1712.05479.

[5] Yongkang Luo, Shizeng Lin, M. Leroux, N. Wakeham, D. M. Fobes, E. D. Bauer, J. B. Betts, J. D. Thompson, A. Migliori, M. Janoschek, Boris Maiorov, in review, arXiv:1711.08873.