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Title: Understanding strain-induced phase transformations in BiFeO 3 thin films

Bismuth ferrite (BiFeO 3) is a promising lead free multiferroic with large polarization, ferroelectricity and robust antiferomagnetism. Experiments demonstrate that epitaxial strain substantially enhance the piezoelectric response of BiFeO 3 thin films. Here, through a synergestic combination of theory and experiments, we characterize the co-existing polymorphs (specifically an intermediate S' phase between the bulk rhombohedral-R and the pseudotetragonal T' phases) observed in strained BiFeO 3 thin films. We show that the S' phase, although energetically very close to the T' phase, exhibits structural similarities with the bulk R phase. G-type antiferromagnetic ordering is predicted for the S' and R phases, whereas, the G/C-type antiferromagnetic order types are energetically indistinguishable for the T' phase. Furthermore, we predict a blue-shift in the band gap Eg when moving from R to S' to T', which we confirm by Electron Energy Loss Spectroscopy measurements. The flat energy landscape and the absence of an energy barrier between the T and S' phases indicate that a reversible phase transformation between the two is possible under the application of an external electric field. This may make it possible to strain engineer the electromechanical response or, utilizing the corresponding changes in Eg, create unique photonic structures.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6] ;  [7] ;  [7] ;  [1]
  1. Oak Ridge National Lab., Oak Ridge, TN (United States)
  2. Oak Ridge National Lab., Oak Ridge, TN (United States); Florida State Univ., Tallahassee, FL (United States); National High Magnetic Field Lab., Tallahassee, FL (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Oak Ridge National Lab., Oak Ridge, TN (United States); ASML, Veldhoven (The Netherlands)
  5. Univ. of Michigan, Ann Arbor, MI (United States); Univ. of California, Los Angeles, CA (United States)
  6. Univ. of Michigan, Ann Arbor, MI (United States)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1342586
Grant/Contract Number:
AC02-05CH11231; FG02-06ER46273; AC02-06CH11357; AC05-00OR22725; DE FG0202ER45998
Type:
Published Article
Journal Name:
Advanced Science
Additional Journal Information:
Journal Name: Advanced Science; Journal ID: ISSN 2198-3844
Publisher:
Wiley
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; multiferroic BiFeO₃; phase coexistence; piezoelectric response; solid-state nudged elastic band method; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY