期刊
PHYSICAL REVIEW B
卷 83, 期 14, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.83.144107
关键词
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资金
- U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division
- Republic of Korea, Ministry of Knowledge and Economy
- Visiting Scientists Program [IAN:16B642601]
- US Department of Energy
- NSF [DMR-0820404, NIRT-0609377]
- UC Santa Barbara under NSF [CHE-0321368]
- [DMR-0940420]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [820404] Funding Source: National Science Foundation
Recent reports on epitaxial BiFeO3 films show that the crystal structure changes from nearly rhombohedral (R like) to nearly tetragonal (T like) at strains exceeding approximate to-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 a symmetry change from M-A and M-C type, respectively, at this R-like-to-T-like transition. Therefore, the ferroelectric polarization is confined to different (pseudocubic) planes in the two phases. 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. Therefore, in going from bulk to highly strained films, a phase sequence of rhombohedral (R)-to-monoclinic (R-like M-A)-to-monoclinic (T-like M-C)-to-tetragonal (T) is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e., near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results now show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone.
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