한국자기학회:학술대회 개요집 (Proceedings of the Korean Magnestics Society Conference)
- 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
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- Pages.7-8
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- 2011
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- 2233-9485(pISSN)
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- 2233-9574(eISSN)
Crystal Structure and Physical Property of Tetragonal-like Epitaxial Bismuth Ferrites Film
- Nam, Joong-Hee (Korea Institute of Ceramic Engineering and Technology) ;
- Biegalski, Michael (Oak Ridge National Laboratory) ;
- Christen, Hans M. (Oak Ridge National Laboratory) ;
- Kim, Byung-Ik (Korea Institute of Ceramic Engineering and Technology)
- 발행 : 2011.06.09
초록
Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for
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