scholarly journals Revealing ferroelectric switching character using deep recurrent neural networks

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Joshua C. Agar ◽  
Brett Naul ◽  
Shishir Pandya ◽  
Stefan van der Walt ◽  
Joshua Maher ◽  
...  
Keyword(s):  
Neural Networks ◽  
Domain Walls ◽  
Hysteresis Loops ◽  
Emergent Properties ◽  
Nanoscale Structures ◽  
Domain Structures ◽  
Latent Features ◽  
Physical Response ◽  
Unsupervised Neural Networks ◽  
Ferroelectric Switching

Abstract The ability to manipulate domains underpins function in applications of ferroelectrics. While there have been demonstrations of controlled nanoscale manipulation of domain structures to drive emergent properties, such approaches lack an internal feedback loop required for automatic manipulation. Here, using a deep sequence-to-sequence autoencoder we automate the extraction of latent features of nanoscale ferroelectric switching from piezoresponse force spectroscopy of tensile-strained PbZr0.2Ti0.8O3 with a hierarchical domain structure. We identify characteristic behavior in the piezoresponse and cantilever resonance hysteresis loops, which allows for the classification and quantification of nanoscale-switching mechanisms. Specifically, we identify elastic hardening events which are associated with the nucleation and growth of charged domain walls. This work demonstrates the efficacy of unsupervised neural networks in learning features of a material’s physical response from nanoscale multichannel hyperspectral imagery and provides new capabilities in leveraging in operando spectroscopies that could enable the automated manipulation of nanoscale structures in materials.

Domain Evolution of Herringbone Structures in Ferroelectric Single Crystals

2010 ◽  
Author(s):  
N. T. Tsou ◽  
J. E. Huber
Keyword(s):  
Single Crystals ◽  
Domain Walls ◽  
Hysteresis Loops ◽  
Domain Pattern ◽  
Domain Evolution ◽  
Domain Structures ◽  
Tetragonal Crystal ◽  
Rank 2 ◽  
Ferroelectric Single Crystal ◽  
Tetragonal Crystal System

The microstructure of a ferroelectric single crystal is significantly affected by applied loads. Domains evolve through equilibrium states, following a route that minimizes the overall energy. The herringbone pattern is one of the most widely observed domain structures in ferroelectric crystals. In this work, the evolution of four types of herringbone pattern in the tetragonal crystal system is studied by using a variational method. These four herringbone patterns are periodic rank-2 laminates which satisfy compatibility across every domain wall. The unit cell of periodic structure dictates a set of domain walls whose positions may vary while maintaining the same topology. The model allows for a crystal with one type of herringbone domain pattern to switch to another pattern through “pivot states”. In this study, a domain evolution map showing all paths between the four types of rank-2 herringbone pattern and their pivot states is developed. Hysteresis loops such as those observed in ferroelectric single crystals subjected to variety of loads are reproduced.

scholarly journals The role of lattice dynamics in ferroelectric switching

2021 ◽  
Author(s):  
Qiwu Shi ◽  
Eric Parsonnet ◽  
Xiaoxing Chen ◽  
Ren-Ci Peng ◽  
Abel Fernandez ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
High Speed ◽  
Critical Role ◽  
Hysteresis Loops ◽  
Piezoresponse Force Microscopy ◽  
Switching Speed ◽  
Domain Structures ◽  
Von Mises ◽  
Ferroelectric Switching

Abstract Reducing the switching energy of ferroelectric thin films remains an important goal in the pursuit of ultralow power ferroelectric memories and magnetoelectric spin-orbit logic devices. Here, we elucidate the fundamental role of lattice dynamics in ferroelectric switching by combining thermodynamic calculations, experiments, and phase-field simulations on both freestanding BiFeO3 membranes and films clamped to a substrate. We observe a distinct evolution of the ferroelectric domain pattern, from striped, 71° ferroelastic domains (spacing of ~100 nm) in clamped BiFeO3 films, to large (10’s of micrometers) 180° domains or even single domain structures, in freestanding films. Through the use of piezoresponse force microscopy, X-ray diffraction, polarization-electric field hysteresis loops, and high-speed pulsed ferroelectric switching experiments, it is found that removing the constraints imposed by the requirement of macroscopic continuity of deformation (also known as the von Mises criterion in the deformation of solids)[1]–[3] to the substrate, we can realize a ~40% reduction of the switching voltage and a consequent ~60% gain in the switching speed. The work highlights the critical role of mechanics and the clamping effect from the substrate in setting the energetics and dynamics of switching in ferroelectrics.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Unsupervised neural networks for automatic Arabic text summarization using document clustering and topic modeling

2021 ◽  
Vol 172 ◽  
pp. 114652
Author(s):  
Nabil Alami ◽  
Mohammed Meknassi ◽  
Noureddine En-nahnahi ◽  
Yassine El Adlouni ◽  
Ouafae Ammor
Keyword(s):  
Neural Networks ◽  
Topic Modeling ◽  
Document Clustering ◽  
Text Summarization ◽  
Arabic Text ◽  
Arabic Text Summarization ◽  
Unsupervised Neural Networks

scholarly journals Mobile and immobile boundaries in ferroelectric films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. Yudin ◽  
K. Shapovalov ◽  
T. Sluka ◽  
J. Peräntie ◽  
H. Jantunen ◽  
...  
Keyword(s):  
Long Range ◽  
Domain Walls ◽  
Ferroelectric Properties ◽  
Practical Importance ◽  
Dynamic Responses ◽  
Ferroelectric Films ◽  
Domain Structures ◽  
Mobile Interfaces ◽  
Ferroelastic Domains ◽  
Viable Method

AbstractThe intrinsic mobile interfaces in ferroelectrics—the domain walls can drive and enhance diverse ferroelectric properties, essential for modern applications. Control over the motion of domain walls is of high practical importance. Here we analyse theoretically and show experimentally epitaxial ferroelectric films, where mobile domain walls coexist and interact with immobile growth-induced interfaces—columnar boundaries. Whereas these boundaries do not disturb the long-range crystal order, they affect the behaviour of domain walls in a peculiar selective manner. The columnar boundaries substantially modify the behaviour of non-ferroelastic domains walls, but have negligible impact on the ferroelastic ones. The results suggest that introduction of immobile boundaries into ferroelectric films is a viable method to modify domain structures and dynamic responses at nano-scale that may serve to functionalization of a broader range of ferroelectric films where columnar boundaries naturally appear as a result of the 3D growth.

Unexpectedly low barrier of ferroelectric switching in HfO2 via topological domain walls

2021 ◽  
Author(s):  
Duk-Hyun Choe ◽  
Sunghyun Kim ◽  
Taehwan Moon ◽  
Sanghyun Jo ◽  
Hagyoul Bae ◽  
...  
Keyword(s):  
Domain Walls ◽  
Topological Domain ◽  
Ferroelectric Switching

Deepening of domains at e-beam writing on the -Z surface of lithium niobate

2021 ◽  
Author(s):  
Lyudmila Kokhanchik ◽  
Evgenii Emelin ◽  
Vadim Vladimirovch Sirotkin ◽  
Alexander Svintsov
Keyword(s):  
Surface Layer ◽  
Electron Beam ◽  
Lithium Niobate ◽  
Electric Field ◽  
Domain Walls ◽  
Normal Component ◽  
Beam Current ◽  
Near Surface ◽  
Domain Structures ◽  
Sign Inversion

Abstract The focus of the study was to investigate the peculiarities of the domains created by electron beam (e-beam) in a surface layer of congruent lithium niobate, which comparable to a depth of electron beam charge penetration. Direct e-beam writing (DEBW) of different domain structures with a scanning electron microscope was performed on the polar -Z cut. Accelerating voltage 15 kV and e-beam current 100 pA were applied. Different patterns of local irradiated squares were used to create domain structures and single domains. No domain contrast was observed by the PFM technique. Based on chemical etching, it was found that the vertices of the domains created do not reach the surface level. The average deepening of the domain vertices was several hundred nanometers and varied depending on the irradiation dose and the location of the irradiated areas (squares) relative to each other. Computer simulation was applied to analyze the spatial distribution of the electric field in the various irradiated patterns. The deepening was explained by the fact that in the near-surface layer there is a sign inversion of the normal component of the electric field strength vector, which controls the domain formation during DEBW. Thus, with the help of e-beam, domains were created completely located in the bulk, in contrast to the domains that are nucleated on the surface of the -Z cut during the polarization inversion with AFM tip. The detected deepening of e-beam domains suggests the possibility of creating the “head-to-head” domain walls in the near-surface layer lithium niobate by DEBW.

COERCIVITY OF SINGLE PINNING CENTER MEASURED BY HALL MICROMAGNETOMETRY

2004 ◽  
Vol 03 (01n02) ◽  
pp. 87-94 ◽  
Author(s):  
KOSTYA S. NOVOSELOV ◽  
SERGEY V. DUBONOS ◽  
SERGEY V. MOROZOV ◽  
DIRK VAN DEN BERGEN ◽  
JAN KEES MAAN ◽  
...  
Keyword(s):  
Coercive Field ◽  
Domain Walls ◽  
Hysteresis Loops ◽  
Nanometer Scale ◽  
Characteristic Energy ◽  
Pinning Centers ◽  
Garnet Films ◽  
Hall Probes ◽  
Pinning Center ◽  
Characteristic Volume

Nanometer-scale movements of domain walls in uniaxial garnet films have been studied by means of micromagnetization measurements using miniature gold and semiconductor Hall probes. At helium temperatures the domain walls are found to move by discrete jumps, which we attribute to pinning on isolated defects, and we were able to measure local hysteresis loops associated with pinning on individual pinning centers. The temperature dependence of the coercive field of a single pinning center allowed us to evaluate the characteristic energy and characteristic volume of the pinning center.

Dynamical aspects of multi-time scale unsupervised neural networks

2006 ◽  
Author(s):  
Anke Meyer-Bäse ◽  
Shantanu Joshi ◽  
Helge Ritter
Keyword(s):  
Neural Networks ◽  
Time Scale ◽  
Unsupervised Neural Networks
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