Avalanches from charged domain wall motion in BaTiO3 during ferroelectric switching

Blai Casals,Ekhard K H Salje,Guillaume F Nataf,David Pesquera

doi:10.1063/1.5128892

Abstract

We report two methods for direct observations of avalanches in ferroelectric materials during the motion of domain walls. In the first method, we use optical imaging techniques to derive changes in domain structures under an electric field. All changes occur through small jumps (jerks) that obey avalanche statistics. In the second method, we analyze jerks by their displacement current. Both methods reveal a power law distribution with an energy exponent of 1.6, in agreement with previous acoustic emission measurements, and integrated mean field theory. This new combination of methods allows us to probe both polarization and strain variations during the motion of domain walls and can be used for a much wider class of ferroelectrics, including ceramic samples, than acoustic emission.

Highlights

Domain boundary engineering,1–3 where domain walls rather than domains are the active elements of a ferroic material, is extensively researched in condensed matter physics
Avalanche dynamics can be probed through scitation.org/journal/apm changes in polarization, by measuring the displacement current,36–44 and through changes in strain, by recording acoustic emission
Optical microscopy gives a direct insight into the jerky motion of domain walls (“watch”), acoustic emission probe results of the strain fields (“listen”), and current measurement changes in polarization (“touch”)

Summary

Introduction

Domain boundary engineering,1–3 where domain walls rather than domains are the active elements of a ferroic material, is extensively researched in condensed matter physics. Jerks occur in both acoustic and electric measurements when domain walls are pinned by defects or because of depolarization fields resulting from local polarization charges.45–47 Simulations show that they are observed in the absence of extrinsic defects in the material and result only from interactions between domain walls.48,49 These processes do not depend on the scale of the energies involved where the same physical process occurs for small and big release mechanisms.

Results

Conclusion