Observation of Néel-Skyrmions in Bilayered Oxide Ferroelectrics.

Gong, Feng-Hui; Yin, Shuai-Shuai; Liu, Kefan; Tang, Yun-Long; Zhu, Yin-Lian; Chen, Yu-Ting; Wang, Yu-Jia; Li, Xiao-Long et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Skyrmions in ferromagnetic materials exhibit either Néel or Bloch characteristics. Although skyrmions in ferromagnetic materials can be readily obtained via inter-spin interactions, a skyrmion in ferroelectric materials exhibiting solely Néel or Bloch characteristics has not yet been discovered. Here, by modulating the formation of skyrmion-bubbles in [(PbTiO<sub>3</sub>)<sub>n</sub>/(SrTiO<sub>3</sub>)<sub>n</sub>]<sub>1</sub> [(PTO<sub>n</sub>/STO<sub>n</sub>)<sub>1</sub>] bilayers grown on STO substrates, the atomic morphology of pure Néel-skyrmion is observed with a topological charge of ± 1 in the ultrathin bilayered films with the thickness of 2 unit cells (u.c.). Such a pure Néel-skyrmion is confirmed by a combination of atomic mappings, geometric phase analysis, and X-ray 3D reciprocal space mapping (RSM). It is found that decreasing the thickness of bilayered films from 50 to 2 u.c., the characteristics of skyrmion-bubbles exhibiting both Néel and Bloch features disappear along with the Bloch features. The formation mechanism of the Néel-skyrmions is unveiled using Phase-field simulations, showing the critical role of electric and gradient energy variation in the stable phase of Néel-skyrmions. These nanoscale pure Néel-skyrmions represent the electrical equivalents of their magnetic counterparts, extending the size limits of topological phases and offering potential advancements in the field of ferroelectric physics.