3D polarization texture of a symmetric 4-fold flux closure domain in strained ferroelectric PbTiO 3 films
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J. Hong Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
E.A. Eliseev Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kyiv 03142, Ukraine
A.N. Morozovska Institute of Physics, National Academy of Sciences of Ukraine, Kyiv 03028, Ukraine
Y.J. Wang, Y. Liu, Y.B. Xu, and B. Wu Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
L.Q. Chen Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
S.J. Pennycook Department of Materials Science and Engineering, National University of Singapore, Singapore 117576, Singapore
X.L. Maa) Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China (Received 18 April 2016; accepted 23 June 2016)
Although the strong coupling of polarization to spontaneous strain in ferroelectrics would impart a flux-closure with severe disclination strains, recent studies have successfully stabilized such a domain via a nano-scaled multi-layer growth. Nonetheless, the detailed distributions of polarizations in three-dimensions (3D) and how the strains inside a flux closure affect the structures of domain walls are still less understood. Here we report a 3D polarization texture of a 4-fold flux closure domain identified in tensile strained ferroelectric PbTiO3/SrTiO3 multilayer films. Ferroelectric displacement analysis based on aberration-corrected scanning transmission electron microscopic imaging reveals highly inhomogeneous strains with strain gradient above 107/m. These giant disclination strains significantly broaden the 90° domain walls, while the flexoelectric coupling at 180° domain wall is less affected. The present observations are helpful for understanding the basics of topological dipole textures and indicate novel applications of ferroelectrics through engineering strains.
I. INTRODUCTION
Various spin textures such as skyrmions, helical orders, flux closures, or vortices have generated great interest recently not only for exploring previously ignored spin interaction mechanisms, but also for potential applications as high performance, low cost memories.1–6 While ferromagnetic exchange favors parallel spin polarizations,2 other mechanisms such as asymmetry Contributing Editor: Rafal Dunin-Borkowski a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.259 J. Mater. Res., 2016
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interactions or demagnetization field tend to swing spins and thus form intriguing spin textures in magnets.1–7 Nevertheless, a precondition for the occurrences of these novel spin structures is that the magnetic anisotropy energies are week forces so that spin can rotate continuously under specific conditions.1,2,7 Ferroelectric materials are the counterpart of ferromagnets. They are polar in st
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