Observation of Néel‐Skyrmions in Bilayered Oxide Ferroelectrics

Abstract

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 3 ) n /(SrTiO 3 ) n ] 1 [(PTO n /STO n ) 1 ] 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.