[19a-133-1~12] 6.1 強誘電体薄膜

[19a-133-7] Elucidation of crystal symmetry and strain of BiFeO₃ epitaxial films on various substrates by structural calculation and electron diffraction

〇永沼 博^1,7、In-Tae Bae¹、一ノ瀬 智浩²、Andras Kovacs³、安井 伸太郎⁴、Hong Zhao⁵、Iniguez Jorge⁵、Han Myung-Geun⁶ (1.Univ. NY、2.東北大、3.ER-C Peter Grunberg Inst.、4.東工大、5.LIST、6.Brookhaven Nat. Lab.、7.CNRS/Thales)

キーワード：構造解析、BiFeO3

Recent resurgence of bismuth ferrite (BiFeO₃) as a multiferroic materials was triggered by the revelation of its true bulk physical properties in the mid 2000s. Subsequently, multiferroic properties of BiFeO₃ have been found to improve when it is grown epitaxial film owing to biaxial strain applied through substrate materials. Since crystal and micro structural modifications caused by the strain dominate the multiferroic property changes in BiFeO₃, tremendous efforts have been devoted to investigate structural changes in epitaxial BiFeO₃ film. However, details about strain-induced structural modification remain elusive due to its remarkably complex nature. In this study, ¹⁾ we systematically discuss: (i) what are pros and cons between transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques, (ii) a methodology about how to apply TEM and XRD to unambiguously identify crystal symmetries in epitaxial BiFeO₃, and (iii) once crystal symmetries is clearly identified, how misfit strain can be accurately evaluated.