Abstract
The structural features of the charge ordering states in are characterized by in situ cooling transmission electron microscopy observations from 300 K down to 20 K. Two distinctive structural modulations, a major and a weak , have been well determined at the temperature of . Systematic analysis demonstrates that the charges at low temperatures are well crystallized in a charge-stripe phase, in which the charge-density wave behavior in a nonsinusoidal fashion results in elemental electric dipoles for ferroelectricity. It is also noted that the charge ordering and ferroelectric domains often change markedly with lowering temperatures and yield a rich variety of structural phenomena.
- Received 19 November 2006
DOI:https://doi.org/10.1103/PhysRevLett.98.247602
©2007 American Physical Society