Observation of Unconventional Dynamics of Domain Walls in Uniaxial Ferroelectric Lead Germanate

Abstract

Application of scanning probe microscopy techniques such as piezoresponse force microscopy (PFM) opens the possibility to re-visit the ferroelectrics previously studied by the macroscopic electrical testing methods and establish a link between their local nanoscale characteristics and integral response. The nanoscale PFM studies and phase field modeling of the static and dynamic behavior of the domain structure in the well-known ferroelectric material lead germanate, Pb 5 Ge 3 O 11 , are reported. Several unusual phenomena are revealed: 1) domain formation during the paraelectric-to-ferroelectric phase transition, which exhibits an atypical cooling rate dependence; 2) unexpected electrically induced formation of the oblate domains due to the preferential domain walls motion in the directions perpendicular to the polar axis, contrary to the typical domain growth behavior observed so far; 3) absence of the bound charges at the 180° head-to-head (H-H) and tail-totail (T-T) domain walls, which typically exhibit a significant charge density in other ferroelectrics due to the polarization discontinuity. This strikingly different behavior is rationalized by the phase field modeling of the dynamics of uncharged H-H and T-T domain walls. The results provide a new insight into the emergent physics of the ferroelectric domain boundaries, revealing unusual properties not exhibited by conventional Isingtype walls.

Topological polarization networking in uniaxial ferroelectrics

“…In addition to the neutral 180 • domain walls, there are also sections of the domain boundaries that correspond to the H-H and T-T arrangements. This observation corroborates the previously reported domain walls features 15,16 by showing that PGO is an unusual example of a uniaxial proper ferroelectric that readily develops uncharged T-T and H-H domain walls.…”

Crackling noise and avalanches in minerals

“…We know today that a transistor, as an example, does not need bulk materials to operate but is often localized in tiny areas inside twin boundaries or near junctions between boundaries. The same holds for ferroic memories and memristive conductors (Salje et al 2017a;He et al 2019;Bak et al 2020;Lu et al 2020a;Zhang et al 2020;Salje 2021) where only a few atoms near domain boundaries move. The diameters or thicknesses of these functional regions are a few inter-atomic distances (Lu et al 2019(Lu et al , 2020bMcCartan et al 2020).…”

Characterization of ferroelectric domain walls by scanning electron microscopy

“…To verify that SEM contrast originates from ferroelectric domains, the domains may be switched with the electron beam, analogous to PFM studies, where the switching is realized using an electrically biased AFM tip. 70,80,81 If the detected contrast inverts along with the polarization orientation, this is a strong indication that the SEM contrast is of ferroelectric origin. Focusing the electron beam with a high current onto a small region has been demonstrated to create a sufficiently high electric field that can switch the polarization direction.…”