Double-Bilayer polar nanoregions and Mn antisites in (Ca, Sr)3Mn2O7
Abstract
The layered perovskite Ca3Mn2O7(CMO) is a hybrid improper ferroelectric candidate proposed for room temperature multiferroicity, which also displays negative thermal expansion behavior due to a competition between coexisting polar and nonpolar phases. However, little is known about the atomic-scale structure of the polar/nonpolar phase coexistence or the underlying physics of its formation and transition. In this work, we report the direct observation of double bilayer polar nanoregions (db-PNRs) in Ca2.9Sr0.1Mn2O7using aberration-corrected scanning transmission electron microscopy (S/TEM). In-situ TEM heating experiments show that the db-PNRs can exist up to 650 °C. Electron energy loss spectroscopy (EELS) studies coupled with first-principles calculations demonstrate that the stabilization mechanism of the db-PNRs is directly related to an Mn oxidation state change (from 4+ to 2+), which is linked to the presence of Mn antisite defects. These findings open the door to manipulating phase coexistence and achieving exotic properties in hybrid improper ferroelectric.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 22, 2022
- Source ID
- 10.1038/s41467-022-32090-w
Entities
People
- Debangshu Mukherjee
- Elizabeth Nowadnick
- Ke Wang
- Kishwar-e Hasin
- Leixin Miao
- Nasim Alem
- Parivash Moradifar
- Sang-Wook Cheong
Organizations
- Air Force Office of Scientific Research
- Gordon and Betty Moore Foundation
- National Science Foundation
- United States Department of Energy