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We compare the magnetism of single crystals of the intercalated transition metal dichalcogenides Cr 1/3 NbS 2 and Mn 1/3 NbS 2 using techniques such as dc and ac susceptibility and Lorentz transmission electron microscopy (LTEM). We present a detailed structural investigation of these materials using electron and single-crystal x-ray diffraction measurements to show how substitutional disorder and stacking faults can manifest in Cr 1/3 NbS 2 and Mn 1/3 NbS 2 , and give rise to additional superlattice reflections in diffraction patterns acquired from Mn 1/3 NbS 2 . Magnetic susceptibility and LTEM measurements show Cr 1/3 NbS 2 displays chiral helimagnetism below its magnetic ordering temperature (T C ) of 111 K, while there is no evidence that Mn 1/3 NbS 2 exhibits helimagnetic ordering below its transition temperature T C = 45 K.

We present longitudinal-field muon-spin relaxation (LF μSR) measurements on two systems that stabilize a skyrmion lattice (SkL): Cu 2 OSeO 3 , and Co x Zn y Mn 20−x−y for (x, y) = (10, 10), (8, 9), and (8, 8). We find that the SkL phase of Cu 2 OSeO 3 exhibits emergent dynamic behavior at megahertz frequencies, likely due to collective excitations, allowing the SkL to be identified from the μSR response. From measurements following different cooling protocols and calculations of the muon stopping site, we suggest that the metastable SkL is not the majority phase throughout the bulk of this material at the fields and temperatures where it is often observed. The dynamics of bulk Co 8 Zn 9 Mn 3 are well described by 2 GHz excitations that reduce in frequency near the critical temperature, while in Co 8 Zn 8 Mn 4 we observe similar behavior over a wide range of temperatures, implying that dynamics of this kind persist beyond the SkL phase.