Straight Domain Research Articles

Influence of magnetic field and ferromagnetic film thickness on domain pattern transfer in multiferroic heterostructures

We report on domain pattern transfer from a ferroelectric BaTiO3 substrate to a CoFeB wedge film with a thickness of up to 150nm. Strain coupling to domains in BaTiO3 induces a regular modulation of uniaxial magnetic anisotropy in CoFeB via an inverse magnetostriction effect. As a result, the domain structures of the CoFeB wedge film and BaTiO3 substrate correlate fully and straight ferroelectric domain boundaries in BaTiO3 pin magnetic domain walls in CoFeB. We use X-ray photoemission electron microscopy and magneto-optical Kerr effect microscopy to characterize the spin structure of the pinned domain walls. In a rotating magnetic field, abrupt and reversible transitions between two domain wall types occur, namely, narrow walls where the magnetization vectors align head-to-tail and much broader walls with alternating head-to-head and tail-to-tail magnetization configurations. We characterize variations of the domain wall spin structure as a function of magnetic field strength and CoFeB film thickness and compare the experimental results with micromagnetic simulations.

Remarkable variability in dyke features at the Vicuña Pampa Volcanic Complex, Southern Central Andes

AbstractDykes at the Vicuña Pampa Volcanic Complex, which are mostly basaltic (trachy)‐andesite and (trachy)‐andesite, are exposed at the base and along the walls of a large depression resulting from intense degradation. Dykes intruding stiff layers (lavas, plugs and necks) are thin, mostly dip >60° and have coherent textures, whereas dykes intruding more compliant materials (breccias and conglomerates) tend to be thicker, have lower dips and have coherent, brecciated or mixed textures (coherent and brecciated textural domains in a single or compound dyke). Single dykes with brecciated and mixed textures are only found intruding near‐surface units. Dykes with mixed textures always have sharp contacts between domains. Dykes with sinuous domain contacts and enclaves of one domain inside the other are interpreted as resulting from dyke arrest, partial cooling and reinjection of new magma. Dykes with straight domain contacts are considered to be compound dykes, with a new dyke intruding along the margins of an older, solidified one.

Shear zone junctions: Of zippers and freeways

Ductile shear zones are commonly treated as straight high-strain domains with uniform shear sense and characteristic curved foliation trails, bounded by non-deforming wall rock. Many shear zones, however, are branched, and if movement on such branches is contemporaneous, the resulting shape can be complicated and lead to unusual shear sense arrangement and foliation geometries in the wall rock. For Y-shaped shear zone triple junctions with three joining branches and transport direction at a high angle to the branchline, only eight basic types of junction are thought to be stable and to produce significant displacement. The simplest type, called freeway junctions, have similar shear sense in all three branches. The other types show joining or separating behaviour of shear zone branches similar to the action of a zipper. Such junctions may have shear zone branches that join to form a single branch (closing zipper junction), or a single shear zone that splits to form two branches, (opening zipper junction). All categories of shear zone junctions show characteristic foliation patterns and deflection of markers in the wall rock. Closing zipper junctions are unusual, since they form a non-active zone with opposite deflection of foliations in the wall rock known as an extraction fault or wake. Shear zipper junctions can form domains of overprinting shear sense along their flanks. A small and large field example are given from NE Spain and Eastern Anatolia. The geometry of more complex, 3D shear zone junctions with slip parallel and oblique to the branchline is briefly discussed.

Local ferroelectricity at the domain walls and stripe domain heads in iron garnet films

ABSTRACTThe concept of local ferroelectricity discussed in this paper belongs to the emerging field of ultrathin multiferroics. The idea of the ferroelectric polarization associated with the domain walls in magnets proposed by V.G. Bar'yakhtar et al. more than thirty years ago has recently got experimental evidence including electric field driven magnetic domain wall motion and electric field induced Stark shift in the single molecule microscopy. The special attention is paid here to the magnetoelectric properties of dislocation in stripe domain structure (i.e. the stripe domain heads) that differ considerably from the ones of straight domain wall segments. It is shown that the electric field induced displacement of the domain wall can be increased by an order of value with external constant magnetic field.

Direct Observation of Ferroelectric Domain Walls in LiNbO3: Wall‐Meanders, Kinks, and Local Electric Charges

Direct observations of the ferroelectric domain boundaries in LiNbO3 are performed using high‐resolution high‐angle annular dark field scanning transmission electron microscopy imaging, revealing a very narrow width of the domain wall between the 180° domains. The domain walls demonstrate local side‐way meandering, which results in inclinations even when the overall wall orientation follows the ferroelectric polarization. These local meanders contain kinks with “head‐to‐head” and “tail‐to‐tail” dipolar configurations and are therefore locally charged. The charged meanders are confined to a few cation layers along the polarization direction and are separated by longer stretches of straight domain walls.

Domain wall generated by graded interlayer coupling in Co/Pt/Co film with perpendicular anisotropy

A magnetic multilayer of the structure substrate/Pt-15 nm/Co-0.8 nm/Pt-wedge(0-7 nm)/Co-0.6 nm/Pt-2 nm is characterized by perpendicular anisotropy of both Co layers. For a Pt spacer thickness tPt≤2.6nm, the magnetization reversal of the Co-layers occurs cooperatively, while for larger tPt, it occurs sequentially. The Co-layer with 0.6 nm thickness (CoS) is magnetically softer than the second one (CoH). In the 2.6≤tPt≤3.0 nm range, there are significant changes of the switching field due to a strong gradient of the interlayer coupling. In this region, the magnetization reversal in the CoS layer takes place reversibly by the propagation of a single, straight domain wall. This specific nature of magnetization reversal is explained by a decelerated motion of the domain wall observed both for the direction corresponding to the increasing, as well as decreasing coupling energy.

Ultrathin Bi(110) films onSi(111)3×3−Bsubstrates

We studied the structure of ultrathin Bi(110) films on $\mathrm{Si}(111)\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\text{\ensuremath{-}}\mathrm{B}$ substrates using scanning tunneling microscopy. Atomically flat Bi islands were nucleated on the substrates at room temperature. The edges of these islands were parallel to the short side of the Bi(110) rectangular unit cell. The islands extended along six specific orientations because the rectangular Bi(110) and rhombus $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ unit cells were commensurate at the interface. Bi(110) domains along different orientations coexisted and formed various domain boundary structures on the wide terraces of the islands. In particular, the domains along $\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0.16em}{0ex}}{87}^{\ensuremath{\circ}}$ from the ${1\overline{1}0}$ direction were connected perfectly on an atomic scale by changing the direction of the $p$-like bond of the in-plane zigzag chains locally at the straight domain boundary. No exclusive preference for the black phosphorus structure was observed for the Bi(110) ultrathin films, in contrast to the islands grown on the $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ substrate.

In situ video-scanning tunneling microscopy studies of the structure and dynamics of Cl adlayers on Au(1 0 0) electrodes

The chloride adlayer on Au(100) electrodes in 0.01M HCl solution was studied on the atomic scale by in situ high-speed scanning tunneling microscopy. In the potential regime 0–0.4VAg/AgCl a hitherto not reported defective c(2×2) structure was observed. In addition to characteristic straight domain boundaries oriented along the [010] and [011] directions of the Au substrate, unusual chain-like adsorbate structures were found. These defects can exhibit open structures with locally lower coverage as well as more close-packed arrangements, in which the adsorbates deviate from the lattice sites and have a 15% reduced nearest neighbor spacing. Dynamic fluctuations within the adlayer occur on the time scale of seconds, much slower than in Cl adlayers on Cu(100). The increase in defect density observed toward more positive potentials suggests a change of the adsorbate–adsorbate interactions with potential.

Manipulation of domain wall mobility by oxygen vacancy ordering in multiferroic YMnO3

The mobility of the ferroelectric domain phases and the local conductivity of ferroelectric domain walls in multiferroic YMnO3 crystals grown in air and reduced atmosphere were studied by piezoresponse force microscopy (PFM), tip-enhanced Raman spectroscopy (TERS) and conductive atomic force microscopy (CAFM). Oxygen vacancies were found to reduce the strength of 4d-2p (Y(3+)-O(2-)) hybridization and structural trimerization distortion, leading to the disappearance of the six wedge-shaped ferroelectric domain phases in oxygen deficient YMnO3-δ crystals. We observed anisotropic domain wall motion such that the wedge-shaped domain configuration joined at one point could be changed to the stripe domain configuration by applying high electric fields in oxygen deficient YMnO3-δ single crystals. The local conductivity of the domain walls increased significantly in poled YMnO3-δ single crystals. The straight conductive domain walls in YMnO3-δ, instead of the twisted insulating ones in the stoichiometric crystal, are induced by the ordered oxygen vacancies which are verified by TERS measurements.

The Structure of Subunit E of the Pyrococcus horikoshii OT3 A-ATP Synthase Gives Insight into the Elasticity of the Peripheral Stalk

A1AO ATP synthases are the major energy converters of archaea. They are composed of an A1 region that synthesizes ATP and an integral part AO that conducts ions. Subunit E is a component of the peripheral stalk that links the A1 with the AO part of the A-ATP synthase. We have determined the crystal structure of the entire subunit E (PhE) of the Pyrococcus horikoshii OT3 A-ATP synthase at 3.6 Å resolution. The structure reveals an extended S-shaped N-terminal α-helix with 112.29 Å in length, followed by a globular head group. The S-shaped feature, common in elastic connectors and spacers, would facilitate the storage of transient elastic energy during rotary motion in the enzyme. The structure has been superimposed into the asymmetric peripheral stalks of the three-dimensional reconstruction of the Pyrococcus furiosus enzyme, revealing that the S-shaped subunit PhE fits well into the bent peripheral stalk, whereas the previously solved E subunit structure (3.1 Å resolution) of Thermus thermophilus A-ATP synthase is well accommodated in the density of the straight stator domain. The different features of the two stalk subunits are discussed in light of a novel coupling mechanism in A-ATP synthases proposed to differ from the Wankel engine of F-ATP synthases.

Oxygen-vacancy effect on structural, magnetic, and ferroelectric properties in multiferroic YMnO3 single crystals

We have investigated the structural, magnetic, and ferroelectric properties of magnetically frustrated multiferroic YMnO3 single crystals. The ferroelectric domain structures of YMnO3 samples were studied by piezoresponse force microscopy. Instead of domain vortex structure in stoichiometric crystals, YMnO3−δ exhibits a random domain configuration with straight domain walls. In magnetic measurements, the YMnO3−δ crystal shows typical antiferromagnetic behavior with higher Néel temperature and lower magnetization compared to the stoichiometric sample. The ordered oxygen vacancies dominate multiferroicity through tailoring the domain wall structure.

Stability of topological defects in chiral superconductors: London theory

This paper examines thermodynamic stability of chiral domain walls and vortices - topological defects which can exist in chiral superconductors. Using London theory it is demonstrated that at sufficiently small applied and chiral fields the existence of domain walls and vortices in the sample is not favored and the sample's configuration is a single domain. The particular chirality of the single-domain configuration is neither favored nor disfavored by the applied field. Increasing the field leads to an entry of a domain wall loop or a vortex into the sample. Formation of a straight domain wall is never preferred in equilibrium. Values of the entry (critical) fields for both types of defects, as well as the equilibrium size of the domain wall loop, are calculated. We also consider a mesoscopic chiral sample and calculate its zero-field magnetization, susceptibility and a change in the magnetic moment due to a vortex or a domain wall entry. We show that in a case of a soft domain wall whose energetics is dominated by the chiral current (and not by the surface tension) its behavior in mesoscopic samples is substantially different from that in the bulk case and can be used for a controllable transfer of edge excitations. The applicability of these results to Sr2RuO4 - a tentative chiral superconductor - is discussed.

Tem analyses of the local crystal and domain structures in (na1-xkx)0.5bi0.5tio3perovskite ceramics

The local crystal and domain structures of the ((Na(1-x)K(x))(0.5)Bi(0.5)TiO(3) (NBT-KBT) solid solutions were studied because of their influence on the enhanced electromechanical properties of ceramics. Based on X-ray diffraction, the morphotropic phase boundary (MPB) was determined for the composition x = 0.20, in which the rhombohedral and the tetragonal structures were observed to coexist. However, detailed domain-structure analyses using transmission electron microscopy (TEM), performed on the NBT, KBT, and five NBT-KBT solid-solution compositions, revealed some structural changes at/near the MPB. In the samples on the tetragonal side of the MPB, the grains showed a lamellar domain structure with 90° orientations of the individual domains, separated by straight domain boundaries, i.e., (011)/(101) twin planes. The rhombohedral samples on the other side of the MPB showed a typical square-net pattern with needle-like or lamellar ~71°/109° rhombohedral domains with (001) and/or (110) twin planes separating the individual domains. The domain structure at the MPB showed well-defined lamellar domains. Based on the occurrence of the superstructure reflections in the SAED patterns of various crystallographic zones, on the characteristic splitting of the reflections, and on the domain morphology observations, the crystal structure in/near the boundary region was determined to be a tetragonal structure with an in-phase oxygen octahedral tilt system (probably a(0)a(0)c(+)). It is suggested that the tetragonal polar order is partly induced from the rhombohedral structure at the MPB as a result of mechanical loading during TEM sample preparation.

Domain-wall and reverse-domain superconducting states of a Pb thin-film bridge on a ferromagnetic BaFe12O19single crystal

We report on imaging of the nonuniform superconducting states in a Pb thin film bridge on top of a ferromagnetic BaFe_{12}O_{19} single crystal with a single straight domain wall along the center of the bridge by low-temperature scanning laser microscopy. We have visualized domain wall superconductivity (DWS) close to the critical temperature of Pb, when the Pb film above the domain wall acts as a superconducting path for the current. The evolution of the DWS signal with temperature and the external-field-driven transition from DWS to reverse domain superconductivity was visualized.

Unique vortex and stripe domain structures in PbTiO 3 epitaxial nanodots

The domain structures of PbTiO 3 epitaxial nanodots under the influences of depolarization fields and mismatch strains have been studied using three dimensional phase field simulations. The single-vortex structure and mixed domain configuration, which consisted of zigzag stripe domain and closure dipole flux near the interfaces, were found to be effective in annihilating the depolarization fields in the isotropically tensile and compressive ferroelectric nanodots, respectively. These domain structures were produced by the combined effect of electrostatic and mismatch elastic energies. The width of stripe domain was found to be related to the volume percentage of polarization dipoles along the z-axis, which varied remarkably with the change of compressive mismatch strain. In the case of nanodots under anisotropic mismatch strains, double-vortex domain patterns and stripe domains with nearly straight domain walls were formed. Moreover, the domain structures with electrostatic energy neglected were also studied.

Block Copolymer Permeable Membrane with Visualized High‐Density Straight Channels of Poly(ethylene oxide)

AbstractA simple fabrication, scalable to centimeter scale, of a permeable membrane made of block copolymer containing molecular transport channels is demonstrated by coating photo‐crosslinkable liquid‐crystalline block copolymer, consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) bearing stilbene (Stb) mesogens in the side chains (PEO114‐b‐PMA(Stb)52), onto a sacrificial cellulose acetate film substrate. After thermal annealing, perpendicularly aligned and hexagonally arranged PEO cylindrical domains with a surface density of 1011 cm−2 were formed and then fixed efficiently by photo‐crosslinking the stilbene moieties in the PMA(Stb) domains by [2 + 2] dimerization. The fully penetrating straight PEO cylindrical domains across the 480‐nm‐thick membrane were well‐defined and visualized as molecule‐transport channels. After exfoliated by removal of the cellulose acetate layer, the membrane could be transferred onto another substrate by either scooping or a horizontal lifting method. Throughout the processes, the fully penetrating PEO channels across the membrane are preserved to open at both ends. A simple permeation experiment demonstrates that rhodamine dyes permeate efficiently through the PEO cylindrical channels of the annealed membrane but not across a non‐annealed one.

Nanomechanical torque magnetometry of permalloy cantilevers

There is mounting interest in bridging the fields of nanomechanics and nanomagnetism. Metallic nanocantilevers, which are magnetic throughout their volume, were fabricated using permalloy in order to detect domain switching along the cantilever length through mechanical deflection driven by magnetic torque. A finite element model describing the interaction of the magnetization of the cantilever with an external driving field is discussed, and illustrated for the simple example of magnetization reversal via propagation of a straight domain wall. The interferometrically obtained cantilever deflection through the magnetic actuation of the fundamental mode exhibits magnetic hysteresis. The experimental results are also compared to the finite element mechanical transformation of the output from a Landau–Lifshitz–Gilbert based micromagnetic simulation of the hysteresis.

Enhanced soft magnetic properties and magnetocaloric effect in B substituted amorphous Fe–Zr alloy ribbons

Abstract Magnetic properties and magnetocaloric effect in amorphous Fe 89− x B x Zr 11 ( x = 0–10) alloys prepared by melt spinning technique have been investigated. The crystallization temperature, Curie temperature ( T C ), and room temperature saturation magnetization ( M S ) of the alloys increase almost linearly with B addition. Coercivity decreases from 13 Oe to 0.015 Oe with the addition of 5 at.% B and then increases to 0.063 Oe for the alloy with 10 at.% B. Low temperature thermomagnetization curves of Fe 89 Zr 11 alloy show a bifurcation between field-cooled and zero-field-cooled curves below 35 K. No such bifurcation was observed in the alloys containing B. High temperature thermomagnetic curves indicate an amorphous-to-crystalline transition above 800 K corresponding to the precipitation of α-Fe phase. These studies reveal that addition of B not only enhances the crystallization temperature, but also decreases the degree of competition between ferromagnetic and antiferromagnetic interactions and there by enhances the soft magnetic nature of the alloys. Magnetic domain structure shows large-sized domains with smooth and relatively straight domain walls for the Fe 84 B 5 Zr 11 alloy. The magnetic domain structure analysis is used to understand the origin of the ultralow coercivity in these alloys. Due to the enhanced soft magnetic properties of these alloys and the possibility of tuning T C and M S by B addition, change in magnetic entropy (Δ S M ) was also investigated. Δ S M showed enhancement from 1.3 J/(kg-K) for the Fe 89 Zr 11 alloy to 1.73 J/(kg-K) for the Fe 79 B 10 Zr 11 alloy for a field change of 0–18 kOe.

Formation of Self-Assembled Domain Structures in Lithium Niobate Modified by Ar Ions Implantation

Self-assembled formation of dense structures of oriented domain rays under application of uniform electric field was studied in single crystalline lithium niobate wafers with surface layers modified by Ar ion implantation. Two types of domain structures were observed: strictly oriented straight domain rays and cogged ones appeared due to the fingering effect. The piezoresponse force microscopy was used for high-resolution domain imaging. Geometrical characteristics of the domain patterns obtained for different strength of applied field were extracted by statistical analysis. The correlated nucleation mechanism was claimed to be responsible for the formation of observed self-assembled domain structures.

Straight Rings

A (commutative integral) domain is called a straight domain if A ↪ B is a prime morphism for each overring B of A; a (commutative unital) ring A is called a straight ring if A/P is a straight domain for all P ∈ Spec(A). A domain is a straight ring if and only if it is a straight domain. The class of straight rings sits properly between the class of locally divided rings and the class of going-down rings. An example is given of a two-dimensional going-down domain that is not a straight domain. The classes of straight rings, of locally divided rings, and of going-down rings coincide within the universe of seminormal weak Baer rings (for instance, seminormal domains). The class of straight rings is stable under formation of homomorphic images, rings of fractions, and direct limits. The “straight domain" property passes between domains having the same prime spectrum. Straight domains are characterized within the universe of conducive domains. If A is a domain with a nonzero ideal I and quotient field K, characterizations are given for A ↪ (I: K I) to be a prime morphism. If A is a domain and P ∈ Spec(A) such that A P is a valuation domain, then the CPI-extension C(P) := A + PA P is a straight domain if and only if A/P is a straight domain. If A is a going-down domain and P ∈ Spec(A), characterizations are given for A ↪ C(P) to be a prime morphism. Consequences include divided domain-like behavior of arbitrary straight domains.