Abstract
Field induced domain wall displacements define ferroelectric/ferroelastic hysteresis loops, which are at the core of piezoelectric, magnetoelectric and memristive devices. These collective displacements are scale invariant jumps with avalanche characteristics. Here, we analyse the spatial distribution of avalanches in ferroelectrics with different domain and transformation patterns: Pb(Mg1/3Nb2/3)O3–PbTiO3 contains complex domains with needles and junction patterns, while BaTiO3 has parallel straight domains. Nevertheless, their avalanche characteristics are indistinguishable. The energies, areas and perimeters of the switched regions are power law distributed with exponents close to predicted mean field values. At the coercive field, the area exponent decreases, while the fractal dimension increases. This fine structure of the switching process has not been detected before and suggests that switching occurs via criticality at the coercive field with fundamentally different switching geometries at and near this critical point. We conjecture that the domain switching process in ferroelectrics is universal at the coercive field.
Highlights
Field induced domain wall displacements define ferroelectric/ferroelastic hysteresis loops, which are at the core of piezoelectric, magnetoelectric and memristive devices
We combine optical microscopy and statistical analyses to characterize the motion of ferroelastic domain wall during ferroelectric switching in two ferroelectric materials: tetragonal BaTiO3 (BTO), for which avalanches have already been studied with acoustic emission[22], and monoclinic Pb(Mg1/3Nb2/3) O3–PbTiO3 (PMN-PT) close to the morphotropic boundary[44]
Our results suggest that the change of the fractal dimension is the key observable to understand ferroelectric domain motion under electric field and that switching occurs via criticality at the coercive field with fundamentally different switching geometries at and near this critical point
Summary
Field induced domain wall displacements define ferroelectric/ferroelastic hysteresis loops, which are at the core of piezoelectric, magnetoelectric and memristive devices. Our results suggest that the change of the fractal dimension is the key observable to understand ferroelectric domain motion under electric field and that switching occurs via criticality at the coercive field with fundamentally different switching geometries at and near this critical point. This behaviour is seen in PMN-PT and BTO so that we conjecture that the overall domain switching process in ferroelectrics may be universal and show little dependence on the details of the actual domain patterns
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