Abstract
Based on a recently developed combination of layer group analysis with order-parameter symmetry, we study the polarity of antiphase domain boundaries (APBs) and ferroelastic twin boundaries (TBs) in . In addition to the celebrated layer group analysis of domain twins, the present method allows us to investigate tensor properties of domain walls also for the case where order-parameter variables other than the spontaneous ones are active. We find that antiphase boundaries in can carry a polarization if in addition to the spontaneous order parameter a second component, i.e., , develops within the domain wall. This result, which is solely based on symmetry arguments, strongly suggests that polarization in APBs is possible if a phase transition from an Ising-type wall to a Néel- or Bloch-like wall occurs. This is in very good agreement with previous calculations based on Landau-Ginzburg free energy expansions including biquadratic () [A. K. Tagantsev et al. Phys. Rev. B 64, 224107 (2001)] and flexoelectric () coupling terms [A. N. Morozovska et al. Phys. Rev. B. 85, 094107 (2012)]. The present results also unveil a close connection between the recently discovered macroscopic polarization in antiferrodistortive cycloids of ferroelastic domain walls of and a mechanism for explaining polarization of APBs.
2 More- Received 7 August 2020
- Revised 29 September 2020
- Accepted 20 October 2020
DOI:https://doi.org/10.1103/PhysRevB.102.184101
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