Polar meron lattice in strained oxide ferroelectrics

• Published in: Nature materials Vol. 19; no. 8; pp. 881 - 886
• Main Authors: Wang, Y. J., Feng, Y. P., Zhu, Y. L., Tang, Y. L., Yang, L. X., Zou, M. J., Geng, W. R., Han, M. J., Guo, X. W., Wu, B., Ma, X. L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2020; Nature Publishing Group
• Subjects: 639/301/1034/1036; 639/301/119/996; 639/766/119/2792/4129; 639/766/119/544; 639/766/930/2735; Biomaterials; Chemistry and Materials Science; Computer simulation; Condensed Matter Physics; Electron microscopy; Epitaxy; Ferroelectric materials; Ferroelectricity; Ferroelectrics; Ferromagnetic materials; Hypothetical particles; Lead titanates; Materials Science; Microscopy; Morphology; Nanotechnology; Optical and Electronic Materials; Order parameters; Particle theory; Substrates; Topology
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-020-0694-8

A topological meron features a non-coplanar structure, whose order parameters in the core region are perpendicular to those near the perimeter. A meron is half of a skyrmion, and both have potential applications for information carrying and storage. Although merons and skyrmions in ferromagnetic materials can be readily obtained via inter-spin interactions, their behaviour and even existence in ferroelectric materials are still elusive. Here we observe using electron microscopy not only the atomic morphology of merons with a topological charge of 1/2, but also a periodic meron lattice in ultrathin PbTiO 3 films under tensile epitaxial strain on a SmScO 3 substrate. Phase-field simulations rationalize the formation of merons for which an epitaxial strain, as a single alterable parameter, plays a critical role in the coupling of lattice and charge. This study suggests that by engineering strain at the nanoscale it should be possible to fabricate topological polar textures, which in turn could facilitate the development of nanoscale ferroelectric devices. Merons are topological structures, but these have yet to be directly observed in ferroelectrics. Here, by epitaxially straining PbTiO 3 on a SmScO 3 substrate, electron microscopy and phase-field modelling allow the morphology and distribution of merons to be observed.