1. Magnetic Skyrmions with Unconventional Helicity Polarization in a Van Der Waals Ferromagnet
- Author
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Zhang, Chenhui, Liu, Chen, Zhang, Senfu, Zhou, Bojian, Guan, Chaoshuai, Ma, Yinchang, Algaidi, Hanin, Zheng, Dongxing, Li, Yan, He, Xin, Zhang, Junwei, Li, Peng, Hou, Zhipeng, Yin, Gen, Liu, Kai, Peng, Yong, and Zhang, Xi-Xiang
- Subjects
Dzyaloshinskii-Moriya interaction ,helicity ,magnetic skyrmions ,perpendicular magnetic anisotropy ,van der Waals materials ,Physical Sciences ,Chemical Sciences ,Engineering ,Nanoscience & Nanotechnology - Abstract
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) prevails 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, the observation of dipole skyrmions with unconventional helicity polarization in a van der Waals ferromagnet, Fe5- δ GeTe2 , is reported. Combining magnetometry, Lorentz transmission electron microscopy, electrical transport measurements, and micromagnetic simulations, the short-range superstructures in Fe5- δ GeTe2 resulting in a localized DMI contribution, which breaks the degeneracy of the opposite helicities and leads to the helicity polarization, is demonstrated. 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.
- Published
- 2022