Mokhtar Ahmed H, Serban David, Porter Daniel G, Lichtenberg Frank, Collins Stephen P, Bombardi Alessandro, Spaldin Nicola A, Newton Marcus C
School of Physics and Astronomy, University of Southampton. University Road, Southampton, SO17 1BJ, UK.
Beamline I16, Diamond Light Source. Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK.
Nat Commun. 2024 Apr 27;15(1):3587. doi: 10.1038/s41467-024-48002-z.
The three-dimensional domain structure of ferroelectric materials significantly influences their properties. The ferroelectric domain structure of improper multiferroics, such as YMnO, is driven by a non-ferroelectric order parameter, leading to unique hexagonal vortex patterns and topologically protected domain walls. Characterizing the three-dimensional structure of these domains and domain walls has been elusive, however, due to a lack of suitable imaging techniques. Here, we present a multi-peak Bragg coherent x-ray diffraction imaging determination of the domain structure in single YMnO nanocrystals. We resolve two ferroelectric domains separated by a domain wall and confirm that the primary atomic displacements occur along the crystallographic c-axis. Correlation with atomistic simulations confirms the Mexican hat symmetry model of domain formation, identifying two domains with opposite ferroelectric polarization and adjacent trimerization, manifesting in a clockwise arrangement around the hat's brim.
铁电材料的三维畴结构显著影响其性能。诸如YMnO等非本征多铁性材料的铁电畴结构由非铁电序参量驱动，导致独特的六边形涡旋图案和拓扑保护畴壁。然而，由于缺乏合适的成像技术，表征这些畴和畴壁的三维结构一直难以实现。在此，我们展示了通过多峰布拉格相干X射线衍射成像对单个YMnO纳米晶体中的畴结构进行的测定。我们分辨出由畴壁分隔的两个铁电畴，并确认主要原子位移沿晶体学c轴发生。与原子模拟的相关性证实了畴形成的墨西哥帽对称模型，确定了具有相反铁电极化和相邻三聚化的两个畴，表现为围绕帽檐的顺时针排列。
