Nature of the structural symmetries associated with hybrid improper ferroelectricity in C a3X2 O7 (X=Mn and Ti)

Document Type

Article

Publication Date

6-27-2019

Abstract

In hybrid improper ferroelectric systems, polarization arises from the onset of successive nonpolar lattice modes. In this work, measurements and modeling were performed to determine the spatial symmetries of the phases involved in the transitions to these modes. Structural and optical measurements reveal that the tilt and rotation distortions of the MnO6 or TiO6 polyhedra relative to the high symmetry phases driving ferroelectricity in the hybrid improper Ca3X2O7 system (X=Mn and Ti) condense at different temperatures. The tilt angle vanishes abruptly at TT∼400 K for Ca3Mn2O7 (and continuously for X=Ti) and the rotation mode amplitude is suppressed at much higher temperatures TR∼1060 K. Moreover, Raman measurements in Ca3Mn2O7 under isotropic pressure reveal that the polyhedral tilts can be suppressed by very low pressures (between 1.4 and 2.3 GPa) indicating their softness. These results indicate that the Ca3Mn2O7 system provides a platform for strain engineering of ferroelectric properties in film-based systems with substrate-induced strain.

Identifier

85068608601 (Scopus)

Publication Title

Physical Review B

External Full Text Location

https://doi.org/10.1103/PhysRevB.99.224105

e-ISSN

24699969

ISSN

24699950

Issue

22

Volume

99

Grant

EAR 1606856

Fund Ref

National Science Foundation

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