The study of head-to-head and tail-to-tail domain walls in hybrid Improper Ferroelectrics
1Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
* presenting author:MING-HAO LEE,
(Ca,Sr)3Ti2O7 is an improper ferroelectrics where geometrical octahedral rotations, rather than typical cation-anion displacement, induce ferroelectric polarization [Yoon Seok Oh et al., Nature Mater. 14, 407-413, 2014]. Despite the improper-ferroelectrics essence of (Ca,Sr)3Ti2O7, the ferroelectric-domain patterns of this material are macroscopically the same as those in conventional ferroelectrics such as BaTiO3.
This intriguingly similarity poses the fundamental, largely unanswered problem of what the clear boundary between improper ferroelectrics and typical ferroelectrics is. Here we report an atomic-scale observation of ferroelectric head-to-head and tail-to-tail domain walls in (Ca,Sr)3Ti2O7 using transmission electron microscopy and scanning transmission electron microscopy. Electron energy-loss spectroscopy was also conducted on these microscopic two-dimensional areas, altogether revealing that an intricate structure-property entanglement makes improper ferroelectrics microscopically different from typical ferroelectrics.

Keywords: improper ferroelectric