Orientation Of Domain Walls Research Articles

Reorientation of the W′ domain walls in ferroelastic silver niobate crystal

Using a polarizing microscope the temperature dependence of orientation of W′-type domain walls in a ferroelastic AgNbO3 crystal was determined. Results obtained are discussed within the framework of the Sapriel theory in relation to temperature dependence of lattice unit cell parameters. Inversion of the W′-domain wall orientation was observed.

Nanoscale reconstruction of surface crystallography from three-dimensional polarization distribution in ferroelectric barium–titanate ceramics

The three-dimensional orientation of polarization vectors at the surface of ferroelectric barium–titanate (BaTiO3) ceramics is evaluated using voltage-modulated scanning force microscopy (SFM). By applying an ac voltage to the conductive SFM tip, we measure the relative amount of the three orthogonal components Px, Py, and Pz, of the polarization vector at any surface point. The measured polarization orientation together with the actual domain-wall orientation allows a precise reconstruction of the crystallographic orientation of the investigated grains down to a 40 nm resolution. Excellent agreement is obtained when comparing this orientation with the crystallographic reconstruction revealed by etch patterns from the sample surface topography. We show that the surface topography manifests a domain structure, which was present in the past, while the actual ferroelectric domain configuration is revealed by the modulation technique.

Domain wall orientation memory as a result of consecutive ferroic phase transitions

It was shown that pattern of domain structure in ferroic crystals undergoing a sequence of phase transitions, changes and depends on the phase preceding the phase with ferroic arrangement. Two crystals were taken into considerations: β-L1NH4SO4 and (NH4)3H(SeO4)2. The orientation of domain walls, both ferroelectric and ferroelastic, is determined by random domain walls, which appeared in the previous phase both ferroelectric and ferroelastic, or a regular large scale structure, which was found in the vicinity of phase transition in β-LiNH4SO4.

Scanning electron acoustic microscopy for the evaluation of domain structures in BaTiO3 single crystal and ceramics

As a non-destructive and subsurface detecting technique, the scanning electron acoustic microscopy (SEAM) method has been applied to study the ferrodomain structures in ferroelectric BaTiO3 single crystal and ceramics. The domain arrangements and the orientations of domain walls at different geometry structures in the BaTiO3 single crystal, and the relationships of domain structures with surface grains in the BaTiO3 ceramics, have been discussed by analysing the experimental results obtained at different operation conditions. The distributions of electron acoustic signals with modulation frequencies up to 1 MHz have been obtained. The relationship of the electron acoustic signal with incident electron energy has also been studied. Although the thermal wave coupling mechanism makes a certain contribution to the acoustic signal generations, the image contrast of ferrodomains is dominated by differences in the electrical properties of ferroelectric materials. © 1998 Kluwer Academic Publishers

Crystal structure and domain-wall orientations of antiferroelectric

The crystal structure of antiferroelectric with ordered complex perovskite structure was reexamined by TEM (transmission electron microscope). Its domain-wall orientations were investigated by the spontaneous strain method. From the CBED (convergent-beam electron diffraction) patterns, its point group was determined to be orthorhombic mmm. During transition from the high-temperature cubic to low-temperature orthorhombic phase, the prototype cubic cell is monoclinically distorted. The monoclinic cell was found to be contracted along the direction of shifts. The reduced symmetry of the orthorhombic phase transformed from the prototypic phase allows the existence of ten species of domain walls, i.e. six W-walls and four -walls. The breaking of reflection symmetry during transition occurred at (1 0 0), (0 1 0), (0 1 1), and planes of the cubic prototype. These high-symmetry planes correspond to the W-walls in the ferroelastic phase. Taking into account the domain geometry, the and planes are the domain-boundaries and the others can be both and ones. The orientations of -walls calculated from the strain components were approximately , and planes at room temperature. On approaching the transition these -walls tend to orient themselves toward the direction of or domain W-walls.

Light Refraction at the Interface between Coexisting Phases of KHCO3

Polarizing microscope observations of ferroelastic domains which coexist with the monoclinic phase in as-grown KHCO 3 crystals below T c = 318 K are reported. The nature as well as the orientation of the phase boundary are predicted in the frame of the theory of Domain-wall orientations in ferroelastics assuming that the domains are triclinic. Specific light refraction experiments at this interface are carried on and analytical expressions between the angles of incidence and of refraction are established using crystal optics. From measurements of these angles, the orientation of the phase boundary is derived with a precision of about 0.2 degree. The excellent agreement between this orientation and the one predicted from the lattice parameters of the two phases shows that the boundary corresponds to a ferroelastic Domain-wall of the W ′ -type and that the observed domains well consist of a triclinic phase.

Domain pattern formation in epitaxial rhombohedral ferroelectric films. II. Interfacial defects and energetics

The coherency defect technique is developed for the domain pattern energetics in rhombohedral (001) epitaxial ferroelectric films. The coherency defects that are necessary to maintain the epitaxy during the ferroelectric phase transition are considered to be the only sources of elastic strains and stresses (and, correspondingly energy) in the film/substrate system. The coherency defects include: (i) a uniform distribution of edge dislocations which are responsible for the in-plane tension or compression and have Burgers vectors parallel to the interface; and two kinds of mesoscale defects: (ii) Somigliana screw dislocations which are responsible for in-plane shear; and (iii) wedge disclinations which are responsible for the out of plane rotations in neighboring domains. Using this approach, analytical expressions were found for the elastic energy in the film/substrate system for both the {101}-ri/rj and the {100}-ri/rj domain patterns. These two configurations differ by the orientation of domain walls, coherency defect content, and also the morphology of the free surface (flat versus puckered surfaces). Calculations are performed for screened mesoscale coherency defect configurations that represent a single embedded domain pattern and multidomain patterns. The following mesoscale defect configurations are used for these calculations: Somigliana dislocation dipoles, wedge disclination dipoles, Somigliana dislocation quadrupoles, and disclination quadrupoles. It is predicted that there is no critical thickness for domain pattern formation in rhombohedral ferroelectric epitaxial films. Agreement is shown between experimentally observed domain widths and theoretically predicted values.

Domain microstructure related to lattice distortion in La1-x Pbx MnO3

In this letter we report a transmission electron microscopy investigation of the occurrence of different orientation states in La1-x Pbx MnO3 and demonstrate its correlation with the rhombohedral distortion of this compound. We show that the observed twinned microstructure is consistent with that expected from groupsubgroup relations between the prototype and the room-temperature phase. Domain wall orientations are derived from ferroelastic theory. The relation between the observed distortion and structural parameters is discussed.

Effect of phase transition sequence on the ferroelastic domain structure of (NH4)3H(SeO4)2 at room temperature

Temperature dependent evolution of ferroelastic domain structure in (NH4)3H(SeO4)2 was studied. It was found that ferroelastic domain structure exists in phases III, IV, V and VI. Ferroelastic domain pattern at room temperature depends on which phase IV or II the crystal was transformed to room temperature. Transformation from paraelastic phase I gives very fine domains with different, domain wall orientations which are difficult to determine. Transformation from phase IV to phase III gives a completely different picture of ferroelastic domain, domains are coarse with well defined orientations of their boundaries.

ＭＩＭプロセスによる軟質磁性材料の磁気特性に及ぽすプロセス条件の影響

For miniaturization and complication of the shape of electronic devices in recent years, both high magnetic and mechanical properties are also being required to the soft magnetic components. A metal injection molding(MIM) process has the attributes of forming the high density, complex shaped and high performance components, which seems to be a suitables process for fabricating the higher performance soft magnetic components.In this paper, the effect of MIM process conditions on the magnetic and mechanical properties of soft magnetic materials such as Fe-Ni and Fe-Si alloys were investigated. Although the final density was obtained approximately 96% of theoretical in both steels, the magnetic properties were similar or inferior to that of the pure iron. Especially, the coercive force was increased with an addition of alloying elements, because the orientation of domain walls were prevented from the grain refining and the residual oxides. Generally, taking account of the improvement in the mechanical properties which are superior to that of the conventional P/M materials, it will be able to apply a MIM process to the soft magnetic components.

Stripe domain structures in a thin ferromagnetic film

We present a theory of the stripe domain structure in a thin ferromagnetic film with single-ion easy-axis magnetic anisotropy and long-range dipole interactions, for a wide range of temperatures and applied magnetic field. The domains exist at temperatures below the reorientational phase transition from out-of-plane to in-plane magnetization. The system of stripes can be described as a liquid crystal with a preferred domain-wall orientation. The positional order is destroyed by both thermodynamical meandering of domain walls and by the proliferation of dislocations. Spatial anisotropy generated by the fourth-order exchange energy stabilizes the stripe domain structure and pins its orientation. For any temperature below the reorientational phase transition there exists a critical perpendicular-to-plane magnetic field, which separates multidomain and monodomain states of the film. The theory explains recent experimental observations.

The effect of thermal history on the ferroelectric domain pattern and the dynamics in β-las single crystals

Abstract Investigation of ferroelectric domain structure in β-LAS single crystals showed strong influence of sample's thermal history on it's pattern. The only orientation of domain walls for β-LAS samples “as grown” and after ferroelastic-ferroelectric phase transition is crystallographic direction [100]. Following paraelectric-ferroelectric phase transition two other orientations of domain walls appear: [302] and [30]. It was observed that above mentioned directions correspond to two orientations of “domain texture” found in very narrow temperature range ΔT ∼ 1 deg below Curie temperature (Tc = 462 K). Switching process in β-LAS single crystals in (ac) plane spreads along direction [100] irrespective of ferroelectric domain structure pattern.

On the domain structure in NiF 2: A γ-ray diffraction study

High-resolution γ-ray diffractometry was used to examine the domain wall orientation in magnetically ordered NiF 2. By measuring the splitting of rocking curves a domain structure model could be deduced which differs from Moriya's model Phys. Rev. 117, 635 (1990). It was found that the splitting angle varies as the order parameter.

Electron microscopy studies of domain structure in ferroelectric crystals

Abstract Results of the studies of ferroelectric domain structure and domain wall orientation in GASH and LAS single crystals obtained by the electron microscope decoration method are presented. In addition the influence of lattice defects on the domain pattern and the domain wall thickness in TGS is studied together with the domain wall clamping effect. A possible explanation of the AgCl decoration effect in the case of GASH crystals is given.

Prototype symmetry of the ferroelastic superconductor Y-Ba-Cu-O.

The question of the prototype symmetry of Y-Ba-Cu-O is reassessed in the light of recent electron-diffraction evidence for the existence of a homologous series of ordered phases in this material. It is argued that the apparaently incompatible data regarding the orientations of the various ferroelastic domain walls found in it can be explained by postulating that walls other than the commonly observed {110} walls must be occurring in regions of a specific oxygen stoichiometry only.

Brillouin, Raman and light diffraction study of phase transitions in KLiSO4under a uniaxial stress

The phase transitions between 150 and 300 K in KLiSO4 are studied under an applied stress through the simultaneous observation of Raman and Brillouin spectra and of the diffraction of light by the domain walls. Three distinct phases are identified; it is proved that between 190 and 265 K the sample can consist of the mixing of two phases; the ferroelastic behaviour of the low-temperature phase (T<190 K) is confirmed and the orientations of the related domain walls are defined.

Properties of Dauphiné-twin domain walls in quartz and berlinite.

The Dauphin\'e-twin domain walls in quartz and berlinite are shown to be ferroelectrically polarized, and the relative directions of the polarization vector in the six different orientations of domain walls are determined. Furthermore, a discontinuity in the displacement field is shown to occur at a domain wall, and vertices at which domain walls intersect are shown to be associated with dislocations in the strain field; these dislocations are characterized by their Burgers vectors.

Ferroelastic phase transition in BiVO4: VI. Some comments on the relationship between spontaneous deformation and domain walls in ferroelastics

For pt.V see ibid., vol.16, p.5127 (1983). The relationship between the domain wall orientation and the spontaneous strain in ferroelastics is discussed, with particular reference to the W' walls in BiVO4. The microscopic, wall-defining property is shown to be the coherence of the lattices of the twin components. This concept, commonly used in metallurgy, is valid for both finite and infinitesimal strains and is more fundamental than the macroscopic strain compatibility condition derived by previous workers in the field of ferroelasticity. Observations of domain walls in BiVO4 as a function of temperature are presented which suggest that they may be of importance in determining the properties of the material close to the ferroelastic phase transition.

Ferroelasticity in phase II of synthetic troegerite

The ferroelastic character of Phase II of (AsO4)2H2(UO2)2 · 8H2O is reported. The Aizu species characterizing the transition as well as the corresponding lattice distortion are determined. The spontaneous strain tensors characterizing the different orientation states are calculated. A comparison of the domain structure and the domain wall orientations with Aizu's and Sapriel's theories is presented.

On the width of charged {110} ferroelectric domain walls in potassium niobate

Abstract High-resolution electron micrographs of {110} domain walls are reported for ferroelectric orthorhombic potassium niobate (KNbO3). Some of the difficulties of interpreting such images are discussed. It is shown that (1) charged 60° and/or 120° domain walls are present, (2) the domain wall structure is incoherent with a spatial periodicity of approximately 800 Å, (3) there are significant ionic displacements localized within ≤ 15 Å of the walls, (4) there are probably significant changes in electron density over a relatively wider band (∼50 Å) and (5) there are small local departures of domain wall orientation from {110}.