Investigating skyrmions using muon-spin spectroscopy*

We present the results of muon-spin relaxation measurements on materials hosting a skyrmion lattice (SkL) phase. We argue that the muon is primarily sensitive to the dynamics of the SkL and we have used this property to probe the local magnetism of several distinct skyrmion systems. Here we discuss our recent results on the effect of disorder on the Néel-skyrmion system GaV₄S_(8-y)Se_y [1], where we have used low-level substitution to assess the stability of the SkL. We also discuss Zn-substituted Cu₂OSeO₃, where we show that the splitting of the SkL phase that was previously reported is only observed in polycrystalline samples and reflects the occurrence of several coexisting phases with different Zn content, each distinguished by different magnetic behavior [2]. We support our results with density functional theory calculations of the muon stopping states, that allow us an additional insight into the local environment of the muon probe.

[1] K.J.A. Franke et al., Phys. Rev. B 98, 054428 (2018).
[2] A. Stefancic et al., Phys. Rev. Mat. 2, 111402(R) (2018).