Introduction to Domain Boundary Engineering

Domain Walls ◽  
2020 ◽  
pp. 109-128
Author(s):  
E. K. H. Salje ◽  
G. Lu
Keyword(s):  
Domain Walls ◽  
Bulk Material ◽  
Domain Boundary ◽  
Functional Domain ◽  
The Novel ◽  
Antiphase Boundaries ◽  
Twin Boundaries ◽  
Domain Boundaries ◽  
Device Applications ◽  
Bloch Lines

This chapter introduces research on functional domain boundaries. Ever since the discovery of superconducting twin boundaries in the 1990s, highly conducting, polar, photovoltaic, magnetic, and so on, domain boundaries have been discovered while the same bulk material displays none of these properties. Domain boundaries constitute planar templates for device applications with thicknesses of ca. 1 nm. Domains within domains are then the next step in miniaturization with Bloch lines within domain walls and Bloch points between Bloch lines. In the overwhelming majority of cases, the geometrical template for the functional domain boundaries stems from the ferroelastic domain structure, while antiphase boundaries are equally potential template providers. Complex structures are a particular case because they add vortices and skyrmions to the template topology. Correlations between such sub-structures maintain features like polarity and piezoelectricity in randomized samples where structural averages would not allow macroscopic polar effects. The dynamics of the change of functionality is often much faster than the speed with which twin boundaries move. The novel information carrier is the kink inside twin walls, which moves with supersonic speed.

Magnetic Microstructure of Thin Films and Surfaces: Exploiting Spin-Polarized Electrons in the SEM and STM

1989 ◽  
Vol 151 ◽  
Author(s):  
D. T. Pierce ◽  
M. R. Scheinfein ◽  
J. Unguris ◽  
R. J. Celotta
Keyword(s):  
Sample Preparation ◽  
Domain Walls ◽  
Domain Boundary ◽  
Physical Structure ◽  
Information Storage ◽  
Polarized Electrons ◽  
Fundamental Interest ◽  
Magnetic Microstructure ◽  
Spin Polarized ◽  
Device Applications

ABSTRACTMagnetic microstructure, that is the configuration of domains and domain walls in a magnetic material, is of both fundamental interest and of crucial importance for device applications. For example, the ultimate density of magnetic information storage is limited by the sharpness of a domain boundary. The magnetic microstructure of a thin film or surface depends sensitively on its physical structure which is strongly affected by sample preparation or growth. High resolution magnetization imaging is necessary to determine the domain configuration that occurs for a particular sample preparation and the changes that take place under external perturbations such as applied magnetic field, stress or temperature.

scholarly journals Current vortices and magnetic fields driven by moving polar twin boundaries in ferroelastic materials

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Guangming Lu ◽  
Suzhi Li ◽  
Xiangdong Ding ◽  
Jun Sun ◽  
Ekhard K. H. Salje
Keyword(s):  
Magnetic Fields ◽  
Speed Of Sound ◽  
Magnetic Moment ◽  
Domain Walls ◽  
Domain Boundary ◽  
Polar Vortex ◽  
Magnetic Memory ◽  
Magnetic Element ◽  
Twin Boundaries ◽  
Moving Domain

Abstract Ferroelastic twin boundaries often have properties that do not exist in bulk, such as superconductivity, polarity etc. Designing and optimizing domain walls can hence functionalize ferroelastic materials. Using atomistic simulations, we report that moving domain walls have magnetic properties even when there is no magnetic element in the material. The origin of a robust magnetic signal lies in polar vortex structures induced by moving domain walls, e.g., near the tips of needle domains and near domain wall kinks. These vortices generate displacement currents, which are the origin of magnetic moments perpendicular to the vortex plane. This phenomenon is universal for ionic crystals and holds for all ferroelastic domain boundaries containing dipolar moments. The magnetic moment depends on the speed of the domain boundary, which can reach the speed of sound under strong mechanical forcing. We estimate that the magnetic moment can reach several tens of Bohr magnetons for a collective thin film of 1000 lattice planes and movements of the vortex by the speed of sound. The predicted magnetic fields in thin slabs are much larger than those observed experimentally in SrTiO3/LaAlO3 heterostructures, which may be due to weak (accidental) forcing and slow changes of the domain patterns during their experiments. The dynamical multiferroic properties of ferroelastic domain walls may have the potential to be used to construct localized magnetic memory devices in future.

scholarly journals Ferroelectric switching in ferroelastic materials with rough surfaces

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Guangming Lu ◽  
Suzhi Li ◽  
Xiangdong Ding ◽  
Jun Sun ◽  
Ekhard K. H. Salje
Keyword(s):  
Domain Walls ◽  
Domain Switching ◽  
Bulk Material ◽  
Rough Surfaces ◽  
Atomic Scale ◽  
Bulk Crystals ◽  
Activation Barriers ◽  
Domain Boundaries ◽  
Ferroelectric Hysteresis ◽  
Effective Domain

Abstract Electric switching of non-polar bulk crystals is shown to occur when domain walls are polar in ferroelastic materials and when rough surfaces with steps on an atomic scale promote domain switching. All domains emerging from surface nuclei possess polar domain walls. The progression of domains is then driven by the interaction of the electric field with the polarity of domain boundaries. In contrast, smooth surfaces with higher activation barriers prohibit effective domain nucleation. We demonstrate the existence of an electrically driven ferroelectric hysteresis loop in a non-ferroelectric, ferroelastic bulk material.

scholarly journals Designing antiphase boundaries by atomic control of heterointerfaces

2018 ◽  
Vol 115 (38) ◽  
pp. 9485-9490 ◽  
Author(s):  
Zhen Wang ◽  
Hangwen Guo ◽  
Shuai Shao ◽  
Mohammad Saghayezhian ◽  
Jun Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Nonvolatile Memory ◽  
Domain Walls ◽  
Domain Boundary ◽  
Film Surface ◽  
Single Step ◽  
Extended Defects ◽  
Antiphase Boundaries ◽  
Extended Defect ◽  
Nucleation Mechanisms

Extended defects are known to have critical influences in achieving desired material performance. However, the nature of extended defect generation is highly elusive due to the presence of multiple nucleation mechanisms with close energetics. A strategy to design extended defects in a simple and clean way is thus highly desirable to advance the understanding of their role, improve material quality, and serve as a unique playground to discover new phenomena. In this work, we report an approach to create planar extended defects—antiphase boundaries (APB) —with well-defined origins via the combination of advanced growth, atomic-resolved electron microscopy, first-principals calculations, and defect theory. In La2/3Sr1/3MnO3 thin film grown on Sr2RuO4 substrate, APBs in the film naturally nucleate at the step on the substrate/film interface. For a single step, the generated APBs tend to be nearly perpendicular to the interface and propragate toward the film surface. Interestingly, when two steps are close to each other, two corresponding APBs communicate and merge together, forming a unique triangle-shaped defect domain boundary. Such behavior has been ascribed, in general, to the minimization of the surface energy of the APB. Atomic-resolved electron microscopy shows that these APBs have an intriguing antipolar structure phase, thus having the potential as a general recipe to achieve ferroelectric-like domain walls for high-density nonvolatile memory.

Functional twin boundaries and tweed microstructures: a comparison between minerals and device materials

2014 ◽  
Vol 78 (7) ◽  
pp. 1725-1741
Author(s):  
Oktay Aktas ◽  
Ekhard K. H. Salje
Keyword(s):  
Functional Properties ◽  
Domain Boundary ◽  
Electronic Devices ◽  
Chemical Transport ◽  
Current Development ◽  
Twin Boundaries ◽  
Symmetry Properties ◽  
Domain Boundaries ◽  
Scale Characterization ◽  
Ferroelectric Behaviour

AbstractIn ferroelastic materials, the existence of degenerate strain states leads to the formation of nanoscale microstructures, such as domain boundaries (twin walls) and tweed. As the symmetry properties of microstructures differ from those of the bulk, they may dramatically change the macroscopic properties of a crystal. In addition, they are likely to have functional properties (ferroelecricity, piezoelectricity, magnetism, conductivity and rapid chemical transport) that are absent in the bulk. The existence of functional properties of twin walls, along with the advances in nano-scale characterization, has opened the door to domain boundary engineering, which aims to use domain boundaries as active elements in device materials. Hence, this relatively new field puts ferroelastic twin walls and possibly tweed at the heart of future electronic devices. Ferroelasticity is very common among minerals. Similar to manmade materials, the same crystallographic principles apply, which means that there are many minerals that await discovery for their functional properties. Thus, this review aims to raise attention to the discovery of minerals with functional microstructures. The current development of functional twin boundaries and tweed structures in physics and materials sciences is compared with the traditional observation of such structures in minerals. With an emphasis on chemical transport and piezoelectric/ ferroelectric behaviour, examples of functional microstructures are given from both man-made materials and minerals in addition to a discussion of the origin of polar twin walls and the introduction of a recent experimental technique, resonant piezoelectric spectroscopy (RPS), for their discovery.

Influence of Micropipe and Domain Boundary in SiC Substrate on the DC Characteristics of AlGaN/GaN HFET

2007 ◽  
Vol 556-557 ◽  
pp. 1043-1046 ◽  
Author(s):  
Hiroyuki Sazawa ◽  
Tomohisa Kato ◽  
Kazutoshi Kojima ◽  
K. Furuta ◽  
K. Hirata ◽  
...  
Keyword(s):  
Domain Boundary ◽  
Topographic Analysis ◽  
Raman Analysis ◽  
X Ray ◽  
Free Carriers ◽  
Crystal Imperfections ◽  
Dc Characteristics ◽  
Domain Boundaries ◽  
Gan Hfet ◽  
Gan Crystal

AlGaN/GaN HFETs were fabricated around micropipes and on a domain boundary in a semi-insulating silicon carbide (SI-SiC) substrate and the DC characteristics of the fabricated devices were measured. Devices around micropipe showed no pinch-off or large gate leakage. The devices on the domain boundaries showed no degradation in the performances, even though an X-ray topographic analysis indicated that crystal imperfections, due to the defects, propagated to the GaN layer across the hetero interface. Based on these results, we concluded that micropipe degrades the DC characteristics and that the domain boundary does not affect the DC characteristics. From Raman analysis on the devices around the micropipes, these degradations could be attributed to the free carriers introduced into the GaN crystal by the micropipes.

A Study Of Domain Boundary Structures In Lead Titanate Single Crystals

1991 ◽  
Vol 238 ◽  
Author(s):  
C. C. Chou ◽  
J. Li ◽  
C. M. Wayman
Keyword(s):  
Electron Microscopy ◽  
Single Crystals ◽  
Lead Titanate ◽  
Mixed Type ◽  
Domain Boundary ◽  
Dynamical Theory ◽  
Fringe Contrast ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Contrast Analysis

ABSTRACTDomain boundary structures of flux-grown poly-domain lead titanate single crystals have been studied using transmission electron microscopy. 90° and 180° domain boundaries were seen in the crystals and were systematically analyzed under various diffraction conditions. Although 90° domain boundaries are supposely δ-type boundaries in BaTiO3, our results show that displacement plays an important role at boundaries and the extreme fringe contrast (EFC) behavior of 90° boundaries is of the mixed type. In the present work, an analysis based upon the two beam dynamical theory was conducted and a rule similar to stacking-fault contrast analysis was established to predict the geometric configuration of a 180° domain boundary using EFC behavior. Examples are given and verified by tilting experiments and electron diffraction. The results are consistent and offer a convenient way to distinguish between 90° and 180° boundaries.

Spiral Friction Stir Processing (SFSP) for the Extrusion of Lightweight Alloy Tubes

2012 ◽  
Author(s):  
Fadi Abu-Farha
Keyword(s):  
Friction Stir Processing ◽  
Special Form ◽  
Bulk Material ◽  
Processing Technique ◽  
Grain Structure ◽  
The Novel ◽  
Friction Stir ◽  
Fine Grain ◽  
Processed Material ◽  
Novel Concept

While friction stir processing (FSP) has been used to refine the grain structure in sheet metals, this work explores the potentials of refining the grain structure of bulk material using the friction stirring phenomenon via the novel concept of spiral friction stir processing (SFSP). With this concept, the rotating stirring tool is plunged into the material, rather than being traversed across it as in FSP; this imposes severe plastic deformation on the material while pushing it radially outwards in complex spiral paths. By confining the material within a closed cylindrical die, the processed material is microstructurally-refined while forming a tube via a special form of SFSP called “friction stir back extrusion” (FSBE). The hypothesised concept was investigated using samples from the AA6063-T52 aluminium alloy and the AZ31B-F magnesium alloy. The preliminary results presented here demonstrate the viability of SFSP, and the special form of FSBE, in producing tubular samples that are structurally sound, with no signs of voids or internal channels. Optical microscopy was performed at key locations within selected tube specimens, and the obtained micrographs clearly show the presence of a stir zone with a fine grain structure; grain size measurements demonstrate the effectiveness of the processing technique in refining the microstructure of the starting material.

Microscopic Mechanism and Domain Formation in the Paraelectric to Ferroelectric Phase Transitions in BaTiO3

2007 ◽  
Vol 1034 ◽  
Author(s):  
Marek Pasciak ◽  
Stefano Leoni
Keyword(s):  
Phase Transitions ◽  
Domain Walls ◽  
Ferroelectric Phase ◽  
Domain Boundary ◽  
Ferroelectric Materials ◽  
Cubic Phase ◽  
Microscopic Mechanism ◽  
Microscopic Features ◽  
Dynamics Simulations ◽  
Ferroelectric Phase Transitions

AbstractA design approach to ferroelectric materials critically depends on an accurate description of the microscopic features associated with paraelectric-to-ferroelectric phase transitions. The fine structures of domains, domain walls, and domain boundary dynamics as well as a precise understanding of local atomic displacements can be accessed using adequate potential models based on ab initio calculations and advanced molecular dynamics simulations. For BaTiO3 a complex scenario of microscopic domains in the paraelectric (cubic) phase and in the ferroelectric (tetragonal) phase is obtained. Therein, the static and dynamic role of domain/antidomain features, as well as their dependence on Ti displacements around the <111> manifold is clearly emerging.

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