Low-symmetry monoclinic phases and polarization rotation path mediated by epitaxial strain in multiferroic BiFeO3 thin films

Zuhuang Chen, Zhenlin Luo, Chuanwei Huang, Yajun Qi, Ping Yang, Lu You, Chuansheng Hu, Tao Wu, Junling Wang, Chen Gao, Thirumany Sritharan, Lang Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

206 Scopus citations

Abstract

A morphotropic phase boundary driven by epitaxial strain has been observed in lead-free multiferroic BiFeO3 thin films and the strain-driven phase transitions have been widely reported as iso-symmetric Cc-Cc by recent works. In this paper, it is suggested that the tetragonal-like BiFeO3 phase identified in epitaxial films on (001) LaAlO3 single crystal substrates is monoclinic MC. This MC phase is different from the MA type monoclinic phase reported in BiFeO3 films grown on low mismatch substrates, such as SrTiO3. This is confirmed not only by synchrotron X-ray studies but also by piezoresponse force microscopy measurements. The polarization vectors of the tetragonal-like phase lie in the (100) plane, not the (110) plane as previously reported. A phenomenological analysis is proposed to explain the formation of MC Phase. Such a low-symmetry MC phase, with its linkage to MA phase and the multiphase coexistence open an avenue for large piezoelectric response in BiFeO3 films and shed light on a complete understanding of possible polarization rotation paths and enhanced multiferroicity in BiFeO3 films mediated by epitaxial strain. This work may also aid the understanding of developing new lead-free strain-driven morphotropic phase boundary in other ferroic systems. Strain-mediated polarization rotation for BiFeO3 films is shown in the figure. Starting from the strain-free rhombohedral (R) phase, the strain-induced transition path is R to Ma by compressive strains or R to Mb by tensile strains. At large enough compressive strains, the Ma to Mc phase transition occurs and brings about a sudden increase in the c-lattice parameter. This new rotation path indicates a soft lattice for BiFeO3 and a tunable behavior by strains where the polarization rotation paths could be mediated in the same way as in those driven by electric field, chemical composition, pressure, and temperature.

Original languageEnglish (US)
Pages (from-to)133-138
Number of pages6
JournalAdvanced Functional Materials
Volume21
Issue number1
DOIs
StatePublished - Jan 7 2011

Keywords

  • BiFeO
  • monoclinic phase
  • morphotropic phase boundary
  • multiferroic materials
  • strain

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Electrochemistry

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