Skyrmion helicity, which defines the spin swirling direction, is a fundamental parameter that may be utilized to encode data bits in future memory devices. Generally, in centrosymmetric ferromagnets, dipole skyrmions with helicity of -π/2 and π/2 are degenerate in energy, leading to equal populations of both helicities. On the other hand, in chiral materials where the Dzyaloshinskii-Moriya interaction (DMI) is prevailing and the dipolar interaction is negligible, only a preferred helicity is selected by the type of DMI. However, whether there is a rigid boundary between these two regimes remains an open question. Herein, we report the observation of dipole skyrmions with unconventional helicity polarization in a van der Waals ferromagnet Fe5-δ GeTe2 . Combining magnetometry, Lorentz transmission electron microscopy, electrical transport measurements, and micromagnetic simulations, we demonstrate that the short-range superstructures in Fe5-δ GeTe2 results in a localized DMI contribution, which breaks the degeneracy of the opposite helicities and leads to the helicity polarization. Therefore, the helicity feature in Fe5-δ GeTe2 is controlled by both the dipolar interaction and DMI that the former leads to Bloch-type skyrmions with helicity of ±π/2 whereas the latter breaks the helicity degeneracy. This work provides new insights into the skyrmion topology in van der Waals materials.
|Original language||English (US)|
|Journal||Advanced materials (Deerfield Beach, Fla.)|
|State||Published - Aug 16 2022|
Bibliographical noteKAUST Repository Item: Exported on 2022-10-31
Acknowledged KAUST grant number(s): ORA-CRG10-2021-4665, ORA-CRG8-2019-4081
Acknowledgements: This work was financially supported by King Abdullah University of Science and Technology (KAUST), Office of Sponsored Research (OSR) under the Award Nos. ORA-CRG8-2019-4081 and ORA-CRG10-2021-4665.S.Z. would like to thank the funding support from the National Natural Science Foundation of China (No. 12104197).Y.P. and J.Z. would like to thank the funding support from the National Natural Science Foundation of China (Nos. 51771085, 51801087, and 91962212).K.L. acknowledges support from the US NSF (DMR-2005108).P.L. would like to thank the funding support from the National Natural Science Foundation of China (No. 12074056).This work used the resources of the Supercomputing Laboratory at KAUST.
ASJC Scopus subject areas
- Mechanics of Materials
- Materials Science(all)
- Mechanical Engineering