期刊
NANO LETTERS
卷 18, 期 2, 页码 717-724出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.7b03817
关键词
Bismuth ferrite; ferroelectric polarization; doping; scanning transmission electron microscopy; differential-phase contrast
类别
资金
- Swiss National Science Foundation (SNSF)
- National Research Foundation (NRF) - Korean government [NRF-2017R1A3B1023686]
The ultimate challenge for the development of new multiferroics with enhanced properties lies in achieving nanoscale control of the coupling between different ordering parameters. In oxide-based multiferroics, substitutional cation dopants offer the unparalleled possibility to modify both the electric and magnetic properties at a local scale. Herein it is demonstrated the formation of a dopant-controlled polar pattern in BiFeO3 leading to the spontaneous instauration of periodic polarization waves. In particular, nonpolar Ca-doped rich regions act as spacers between consecutive dopant-depleted regions displaying coupled ferroelectric states. This alternation of layers with different ferroelectric state creates a novel vertical polar structure exhibiting giant polarization gradients as large as 70 mu C cm(-2) across 30 angstrom thick domains. The drastic change in the polar state of the film is visualized using high-resolution differential phase-contrast imaging able to map changes in ferroelectric polarization at atomic scale. Furthermore, a periodic distortion in the Fe-O-Fe bonding angle suggests a local variation in the magnetic ordering. The findings provide a new insight into the role of doping and reveal hitherto unexplored means to tailor the functional properties of multiferroics by doping engineering.
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