Double-Bilayer polar nanoregions and Mn antisites in (Ca, Sr)3Mn2O7

Leixin Miao, Kishwar E. Hasin, Parivash Moradifar, Debangshu Mukherjee, Ke Wang, Sang Wook Cheong, Elizabeth A. Nowadnick, Nasim Alem

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

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 Ca2.9Sr0.1Mn2O7 using 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.

Original languageEnglish (US)
Article number4927
JournalNature communications
Volume13
Issue number1
DOIs
StatePublished - Dec 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy

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