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Collective nonlinear electric polarization via defect-driven local symmetry breaking


In this work, we report the defect-mediated,abnormal non-linear polarization behavior observed in centrosymmetric rutile TiO2 where a small amount (less than 1 at.%) of sterically mismatched Mg2+ ions are introduced to create ferroelectric-like polarization hysteresis loops. It is found that the 〖Mg〗_Ti^''-V_O^•• defect cluster produces a dipole moment exceeding 6 Debye, with a rotatable component. Such a polarization is further enhanced by the displacement of neighboring Ti4+ ions. The coupling between such defect-driven symmetry-breaking regions generates a collective nonlinear electrical polarization state that persists to high temperatures. More importantly, an observation of abnormal bias shift of polarization hysteresis suggests an antiparallel alignment of certain dipoles frozen relative to the external poling electric field, which is associated with oxygen vacancy hopping. This result challenges the long-standing notion of parallel alignment of dipoles with the external electric field in ferroelectrics and reveals an unexpected new form of non-linear dielectric polarization in solid-state materials.

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Publication details

The article was received on 04 Apr 2019, accepted on 17 May 2019 and first published on 17 May 2019

Article type: Communication
DOI: 10.1039/C9MH00516A
Mater. Horiz., 2019, Accepted Manuscript

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    Collective nonlinear electric polarization via defect-driven local symmetry breaking

    W. Dong, D. L. Cortie, T. Lu, Q. Sun, N. Narayanan, W. Hu, Q. Li, D. Yu, H. Chen, A. Chen, X. Wei, G. Wang, M. G. Humphrey, T. J. Frankcombe and Y. Liu, Mater. Horiz., 2019, Accepted Manuscript , DOI: 10.1039/C9MH00516A

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