Abstract
Leveraging competition between energetically degenerate states to achieve
large field-driven responses is a hallmark of functional materials, but routes
to such competition are limited. Here, a new route to such effects involving
domain-structure competition is demonstrated, which arises from straininduced
spontaneous partitioning of PbTiO3 thin films into nearly energetically
degenerate, hierarchical domain architectures of coexisting c/a and a1/a2
domain structures. Using band-excitation piezoresponse force microscopy,
this study manipulates and acoustically detects a facile interconversion of
different ferroelastic variants via a two-step, three-state ferroelastic switching
process (out-of-plane polarized c+ ā in-plane polarized a ā out-of-plane
polarized cā state), which is concomitant with large nonvolatile electromechanical
strains (ā1.25%) and tunability of the local piezoresponse and elastic
modulus (>23%). It is further demonstrated that deterministic, nonvolatile
writing/erasure of large-area patterns of this electromechanical response is
possible, thus showing a new pathway to improved function and properties.
