Avalanche criticality in LaAlO$$_3$$ and the effect of aspect ratio

Abstract

Ferroic domain dynamics, as a function of external stimuli, can be collectively described as scale-invariant avalanches characterised by a critical exponent that are sensitive to the complexity of the domain microstructure. The understanding and manipulation of these avalanches lies at the heart of developing novel applications such as neuromorphic computing. Here we combine in situ heating optical observations and mean-field analysis to investigate the collective domain behaviour in pure-ferroelastic lanthanum aluminate (LaAlO$$_3$$ 3 ) as a function of aspect ratio, the ratio of sample length to width, where the movement of the domains is predominantly driven by thermal stresses via thermal expansion/contraction during heat cycling. Our observations demonstrate that the aspect ratio induces (1) distinctive domain microstructures at room temperature, (2) a deviation of dynamical behaviour at high temperatures and (3) critical exponent mixing in the higher aspect ratio samples that accompanies this behaviour. While the critical exponents of each aspect ratio fall within mean-field predicted values, we highlight the effect that the aspect ratio has in inducing exponent mixing. Hence, furthering our understanding towards tuning and controlling avalanches which is crucial for fundamental and applied research.

Influence of ferroelastic domain walls on thermal conductivity

“…1(b) (sample A) and 1(c) (sample C) are as-received single crystals with a very regular domain pattern, clearly visible because of differences in reflectivity between ferroelastic domains. Domain walls are strictly orthogonal to the surface, indicating that they are planes orthogonal to the [010]pc direction, in agreement with the literature [35,36]. Domain structures observed in Fig.…”

The Effect of Chemical Environment and Temperature on the Domain Structure of Free‐Standing BaTiO3 via In Situ STEM

“…To verify the accuracy of the temperature measurement, a LaAlO 3 (LAO) lamella of similar dimensions was heated under UHV conditions, with identical conditions as the BTO lamella. In this case, the lack of domain contrast was observed near the bulk's T C value [50] (Figure S6 and Video S2, Supporting Information), thus confirming the measured T C by in situ STEM for BTO. As an additional test, in situ UHV temperature-controlled PFM was performed on a sister BTO lamella (Figure S5, Supporting Information) to further investigate the temperature-induced domain behavior and to rule out beam-induced effects by STEM imaging.…”

Dynamic domain boundaries: chemical dopants carried by moving twin walls

“…The second way is to characterize the properties of twin boundaries directly by methods sensitive to their state, including direct observations by means of various types of microscopy. Once it is established that twin boundaries move, their position can be determined by optical inspection 56,57 or by atomic force microscopy, AFM. 58 Using direct observations, the twin boundary patterns can be established, usually by standard micro-manipulators.…”