期刊
PHYSICAL REVIEW LETTERS
卷 109, 期 26, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.109.267601
关键词
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资金
- CEA Ph.D. grant CFR
- ANR
- National Natural Science Foundation of China [11274222]
- ARO [W911NF-12-1-0085]
- ONR [N00014-11-1-0384, N00014-12-1-1034, N00014-08-1-091, N00014-07-1-0825]
- DOE, Office of Basic Energy Sciences [ER-46612]
- NSF [DMR-1066158, DMR-0701558]
- MRI [0722625]
- DOD
- Division Of Computer and Network Systems
- Direct For Computer & Info Scie & Enginr [0959124] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1066158] Funding Source: National Science Foundation
- Office Of The Director
- EPSCoR [0918970] Funding Source: National Science Foundation
We measure the ferroelectric polarization of BiFeO3 films down to 3.6 nm using low energy electron and photoelectron emission microscopy. The measured polarization decays strongly below a critical thickness of 5-7 nm predicted by continuous medium theory whereas the tetragonal distortion does not change. We resolve this apparent contradiction using first-principles-based effective Hamiltonian calculations. In ultrathin films, the energetics of near open circuit electrical boundary conditions, i.e., an unscreened depolarizing field, drive the system through a phase transition from single out-of-plane polarization to nanoscale stripe domains. It gives rise to an average polarization close to zero as measured by the electron microscopy while maintaining the relatively large tetragonal distortion imposed by the nonzero polarization state of each individual domain. DOI: 10.1103/PhysRevLett.109.267601
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