Antiphase Structure Research Articles

Dribble Accuracy and Arm Coordination Pattern According to Motor Expertise and Tempo.

Skilled movements in motor learning result from efficiently controlling the many degrees of freedom in human movement. To acquire motor skills, harmonious coordination of body segments in time and space is crucial for accurate and consistent performance. The purpose of this study was to compare dribbling accuracy, consistency, and coordination patterns of body segments according to motor expertise and tempo. To achieve this, we had eight basketball experts and eight beginners perform static dribbling at three different speeds for 20 s. Force plates measured radial error while motion capture equipment measured the angular data of the right arm's fingers, wrist, and elbow. The measurements obtained from the force plate were used to analyze the participants' dribbling performance, including accuracy, consistency, and coordination patterns. The research results showed that there was no significant difference in dribbling accuracy according to skill level, but skilled players showed higher consistency in the anterior-posterior (AP) direction (p < 0.001). In the comparative analysis of coordination patterns, skilled players showed an in-phase structure, whereas beginners showed an anti-phase structure (elbow-wrist: p < 0.05; wrist-finger: p < 0.001; elbow-finger: p < 0.001). This study suggests that achieving proficiency in basketball dribbling requires a strategy that involves coordination of movements with an in-phase pattern for stability in performance.

Magnetization reversal induced by antiphase domain boundaries in Ni2MnZ Heusler compounds

The correlation of the microstructure and the magnetic properties of ${\mathrm{Ni}}_{\text{2}}{\mathrm{MnAl}}_{\text{0.5}}{\mathrm{Ga}}_{\text{0.5}}$ and ${\mathrm{Ni}}_{\text{2}}\mathrm{MnAl}$ Heusler alloys is studied in samples of distinct $\mathrm{L}{2}_{\text{1}}$ order states by neutron powder diffraction and small-angle scattering. The extracted correlation lengths of the structural and magnetic order agree over all annealing states, which implies the structural antiphase domain boundaries to be identical to the magnetic domain walls, and thus to inherently give rise to a magnetization reversal. The findings are discussed in the context of recent small-angle neutron scattering studies on related systems, and their wider implications are pointed out.

Sinusoidally modulated magnetic structure of Kramers local moments in CePd5Al2

The crystalline electric field (CEF) level scheme and magnetic structure of a tetragonal antiferromagnet CePd5Al2 with K and K were studied by neutron scattering, magnetization and magnetoresistance measurements. Inelastic neutron scattering measurements on the powder sample revealed CEF excitations at 21.3 and 22.4 meV. The derived wave functions of the CEF ground state for the Ce3+ ion consist primarily of under the tetragonal symmetry. By means of single-crystal neutron diffraction, magnetic Bragg peaks characterized by a propagation vector were observed at . Our analysis indicates a sinusoidally modulated magnetic structure with amplitude of 2.0(1) /Ce, where the magnetic moments point to the -axis. The intensity of the third-order harmonic at 0.8 K is 1/30 as small as that expected for an antiphase structure, suggesting that the modulated structure remains at least down to 0.8 K. Both the magnetization and magnetoresistance show several anomalies in the magnetically ordered phase, indicating field-induced successive changes of the magnetic structure.

Elastic constants of boron hydrogen chains in monoclinic crystal

Full-potential linearized augmented plane waves (FPLAPW), density functional theory within the generalized gradient and local density approximations methods are used to determine the ground state structure and to calculate the elastic constants of two phases of boron hydrogen chains in monoclinic crystalline form. The ground state structures are subjected to different strains to find the thirteen elastic constants of both phases by fitting the total energies E (V0,ε) with Birch—Murnaghan equation of state. Young's modulus shows that the anti-phase structure is stiffer than the in-phase one. The calculated ductility index using Pugh's (B/G) ratio found to be less than 0.5 for both phases indicating that they are brittle material.

Robust phase-waves in chains of half-center oscillators.

Many neuronal circuits driving coordinated locomotion are composed of chains of half-center oscillators (HCOs) of various lengths. The HCO is a common motif in central pattern generating circuits (CPGs); an HCO consists of two neurons, or two neuronal populations, connected by reciprocal inhibition. To maintain appropriate motor coordination for effective locomotion over a broad range of frequencies, chains of CPGs must produce approximately constant phase-differences in a robust manner. In this article, we study phase-locking in chains of nearest-neighbor coupled HCOs and examine how the circuit architecture can promote phase-constancy, i.e., inter-HCO phase-differences that are frequency-invariant. We use two models with different levels of abstraction: (1) a conductance-based model in which each neuron is modeled by the Morris-Lecar equations (the ML-HCO model); and (2) a coupled phase model in which the state of each HCO is captured by its phase (the phase-HCO model). We show that one of four phase-waves with inter-HCO phase-differences at approximately 0, 25, 50 or 75% arises robustly as a result of the inter-HCO connection topology, and its robust existence is not affected by the number of HCOs in the chain, the difference in strength between the ascending and descending nearest-neighbor connections, or the number of nearest-neighbor connections. Our results show that the internal anti-phase structure of the HCO and an appropriate inter-HCO connection topology together can provide a mechanism for robust (i.e., frequency-independent) limb coordination in segmented animals, such as the 50% interlimb phase-differences in the tripod gate of stick insects and cockroaches, and the 25% interlimb phase-differences in crayfish and other long-tailed crustaceans during forward swimming.

Nanodomains Coupled to Ferroelectric Domains Induced by Lattice Distortion in Self-Doped LuMnxO3±δ Hexagonal Ceramics

Self-doped h-LuMnxO3±δ multiferroic ceramics with 0.92 ≤ x ≤ 1.12 were studied for the dependence of magnetic properties on x. Interlocking of lattice distortion at the nanoscale with ferroelectric (FE) domains in bulk RMnO3 materials is mostly unknown. Here we report occurrence of nanodomains in transmission electron microscopy (TEM) images with the presence of antiphase boundaries/ferroelectric domain walls separating nano-FE domains. Observed chemical inhomogeneity across the crystalline grains of the ceramics causes distortion in the lattice. Formation of nanostructural domains revealed across particles of Mn deficient or Lu deficient samples includes bands of strained atomic planes, structural antiphase boundaries, and planar defects similar to stacking fault ribbons. Nanotwins exist in the basal plane, the twin boundary representing disorder of the stacking of atomic planes along the [110] direction. Image contrast in high resolution HRTEM images and TEM image simulation confirm the role of planar d...

Antiphase structures in a periodically inverted GaAs/AlGaAs waveguide investigated by transmission electron microscopy

We have performed transmission electron microscopy (TEM) observation of antiphase structures in a periodically inverted GaAs/Al0.1Ga0.9As waveguide fabricated on a (100) GaAs substrate intentionally misoriented toward by 2°. We have unambiguously confirmed that the artificial (011) boundaries between the inverted and noninverted domains are of antiphase nature by TEM observations including conventional dark-field imaging and a two-beam technique. We also investigated unintentionally formed self-annihilating non-inverted GaAs domains grown on a Ge interlayer introduced for growing inverted GaAs epilayers using the sublattice-reversal epitaxy technique.

B23-O-08Microstructures in improper ferroelectric compounds revealed by electron microscopy

In improper ferroelectric materials, the order parameter of the phase transition is not the polarization but another physical quantity, where transformation properties are different from those of the polarization. The spontaneous polarization arises in the phase transition as a secondary effect [1]. For example, geometric ferroelectric such as the hexagonal manganites are improper ferroelectrics in which geometric structural constrains induce ferroelectric polarization [2]. An another example is a hybrid improper ferroelectricity such as (Ca,Sr)3Ti2O7, whichresults from the combination of two or more non-ferroelectric structural order parameters [3]. The coupling between the spontaneous ferroelectric polarization and other physical quantities should result in unique domain structures in the improper ferroelectric materials. Figure 1 is a domain structure in the improper ferroelectric compound BaAl2O4 with the hexagonal structure [4]. Characteristic structural antiphase domains are observed, in which structurally modulated superstructure with 2a ×2a×c. In the presentation, unique charged domain walls found in some improper ferroelectric compounds will be reported. [1] A. P. Levanyuk et al., Sov. Phys. Usp., 17 (1974) 199-214. [2] T. Choi, et al., Nature Mater. 9 (2010) 253-258. [3] Y. S. Oh et al., Nature Mater. 14 (2015) 407-413. [4] S. Mori et al., Ferroelectrics 464 (2014) 116-121. Fig.1 Microstructure in the ferroelectric phase of BaAl2O4. B23-O-07 doi:10.1093/jmicro/dfv165

B23-O-07Multivariate Statistical Analysis of EMCD Spectra measured at the Fe/MgO Interface

In improper ferroelectric materials, the order parameter of the phase transition is not the polarization but another physical quantity, where transformation properties are different from those of the polarization. The spontaneous polarization arises in the phase transition as a secondary effect [1]. For example, geometric ferroelectric such as the hexagonal manganites are improper ferroelectrics in which geometric structural constrains induce ferroelectric polarization [2]. An another example is a hybrid improper ferroelectricity such as (Ca,Sr)3Ti2O7, whichresults from the combination of two or more non-ferroelectric structural order parameters [3]. The coupling between the spontaneous ferroelectric polarization and other physical quantities should result in unique domain structures in the improper ferroelectric materials. Figure 1 is a domain structure in the improper ferroelectric compound BaAl2O4 with the hexagonal structure [4]. Characteristic structural antiphase domains are observed, in which structurally modulated superstructure with 2a ×2a×c. In the presentation, unique charged domain walls found in some improper ferroelectric compounds will be reported. [1] A. P. Levanyuk et al., Sov. Phys. Usp., 17 (1974) 199-214. [2] T. Choi, et al., Nature Mater. 9 (2010) 253-258. [3] Y. S. Oh et al., Nature Mater. 14 (2015) 407-413. [4] S. Mori et al., Ferroelectrics 464 (2014) 116-121. Fig.1 Microstructure in the ferroelectric phase of BaAl2O4. B23-O-07 doi:10.1093/jmicro/dfv165

Spontaneous formation of circular and vortex ferroelectric domain structure in hexagonal YMnO3 and YMn0.9Fe0.1O3 prepared by low temperature solution synthesis

We report an experimental study of the domain structure of ferroelectric YMnO3 and YMn0.9Fe0.1O3 using polycrystalline samples prepared by direct hydrothermal crystallisation at 240 °C, well below their structural phase transition temperatures. Powder X-ray diffraction shows the expected P63cm space group for both samples with an increase in a and a small decrease in c with Fe incorporation, consistent with an adjustment of MnO5 tilting, while XANES spectra at the Mn and Fe K edges show the oxidation state of both metals are maintained at +3 in the doped sample. High resolution TEM shows that curved stripe, annular and vortex domains can all be observed in the YMnO3 crystals, proving that the structural phase transition is not the only driving force for the occurrence of the annular and vortex domains. Furthermore, the absence of the annular and vortex domains in YMn0.9Fe0.1O3 indicates that the tilting state of MnO5 bipyramids plays an important role in the domain formation. Atomic resolution STEM images confirm that the ferroelectric domain walls correspond to structural antiphase boundaries similar to the crystals made via high temperature solid-state reactions.

Effect of chemical ordering on 90° interlayer coupling in epitaxial Co–Fe/Cr/Co–Fe thin films

Interlayer exchange coupling (IEC) was studied in ferromagnetic binary alloy Co–Fe thin films through Cr spacer to investigate systematically, the effects of chemical compositions and the chemical ordering on the observation of 90° interlayer coupling in magnetic alloy based structures. The dominating 180° coupling with weak 90° coupling was observed at room temperature deposited CoxFe1−x/Cr/CoxFe1−x (x=0 to 0.8) trilayer samples for all values of x. However, the strength of the 90° coupling for x=0.4 and 0.5 was found to increase with increasing the annealing temperature, Tann for the bottom CoxFe1−x layer and the strength of 90° coupling became comparable to that of 180° coupling at Tann=400°C. The enhancement of 90° coupling was considered to be originated from the unconventional interfacial magnetic exchange interactions between Cr and Co (and Fe) due to the appearance of antiphase structures at the interface with the enhancement of chemical ordering (B2 ordering) which was confirmed by synchrotron X-ray diffraction.

Ferroelectric and Structural Antiphase Domain and Domain Wall Structures in Y(Mn,Ti)O3

We have investigated ferroelectric (FE) and structural antiphase (SAP) domains and domain wall structures at the atomic scale in hexagonal YMn1-xTixO3-δ by using aberration-corrected high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM) experiments, combining with the conventional TEM observation techniques. Atomic shifts of Y3+ and Mn3+ (Ti4+) in the FE and SAP domains and domain wall structures in YMn1-xTixO3-δ are successfully visualized at the atomic scale. When Ti4+ are substituted for Mn3+, the magnitude of the shifts of Y3+ is reduced and the regions without any displacement of Y3+ along the [001] direction dominated around x-0.40. Our experimental results clearly revealed that partial substitution of Ti4+ for Mn3+ suppress the magnitude of the shifts of Y3+ ions along the [001] direction and the FE properties tend to diminish with increasing the amount of Ti4+ in YMn1-xTixO3-δ.

TREPR spectra of micelle-confined spin correlated radical pairs: I. Molecular motion and simulations

Radical pairs created by the photoreduction of benzophenone (BP) in sodium dodecyl sulfate (SDS) micelles exhibit strong asymmetry in the line shapes of their time-resolved electron paramagnetic resonance (TREPR) signals. The asymmetry is strongly dependent on the temperature from 16 °C to 66 °C. Simulations of the anti-phase structure (APS) line shape of these spin correlated radical pairs (SCRPs), based on a numerical solution of the Stochastic Liouville Equation with the spin exchange interaction depending exponentially on the distance between radicals, are presented and discussed. The proposed model takes into account the diffusive motion of the radicals along with the motion of the transverse magnetization and accounts satisfactorily and self-consistently for the asymmetry of the observed TREPR signals.

TREPR spectra of micelle-confined spin correlated radical pairs: II. Spectral decomposition and asymmetric line shapes

In the second paper, spectral decomposition is used to explain the origin of the asymmetry of the anti-phase structure (APS) and its temperature dependence in dynamic spin correlated radical pairs (SCRPs) created via the photoreduction of benzophenone (BP) in sodium dodecyl sulfate (SDS) micelles. It is shown that the main parameters defining the spectral shape of the TREPR spectra are the effectiveness of the electron spin exchange in contact pairs, and the ratio of the frequency of enforced encounters (Z) to the frequency of singlet-triplet mixing (q) in the separated radical pairs. The Z/q ratio is particularly important for the creation of the APS asymmetry. The existence of different q values in the same TREPR spectrum in this system affords the observation of SCRPs in both regimes: exchange broadening (large |q|/Z) and exchange narrowing (small |q|/Z). An important observation, supported by the successful simulation of the TREPR spectra, is that the S-component of the APS can be shifted in a direction opposite to that predicted by the earlier Closs-Forbes-Norris (CFN) model. This result is naturally explained in terms of a spectral exchange approach. Dispersion-like components in the spectra further amplify the asymmetry of the APS.

Real-space imaging of ferroelectric and structural antiphase domains in hexagonal YMnO3

A high-angle annular-dark-field (HAADF) imaging technique was applied to the investigation of domain wall structures in the ferroelectric phase of hexagonal manganites, YMnO3, on an atomic scale. The displacements of the Y3+ ions along the [001] direction can be clearly visualized. The ferroelectric dipole moments are revealed to be caused by the opposite and unequal displacements of Y3+ ions. Two types of domain walls should be identified in the ferroelectric domain structures. One is charged longitudinal domain walls with head-to-head or tail-to-tail configurations and the other is non-charged transverse domain walls with head-to-tail configurations. In addition, the ferroelectric and the structural antiphase domains in YMnO3 change into fragmentary domains because of substitution of Ti4+ for Mn3+, and ferroelectric nanodomains with sizes of 10–20 nm are found in the x = 0.30 compound.

Compositional evolution of the anti-phase stripe superstructure in Bi2Sr2−xLaxCuO6 (0 < x ≤ 1.1) revealed by transmission electron microscopy

The detailed structural properties of La-doped Bi2Sr2−xLaxCuO6 (La–Bi2201, 0 ≤ x ≤ 1.1) have been studied by transmission electron microscopy (TEM). The well-known incommensurate supermodulation q1 in the Bi-based cuprates evolves from a monoclinic superstructure in the pristine Bi2201 phase to an orthogonal one in the La–Bi2201 (x = 0.73) phase. The b-component of the modulation vector (q1) for the x = 0.25 sample is about 0.24b* and increases slightly to 0.246b* in the x = 0.84 sample, while it increases significantly to 0.286b* for the x = 1.10 sample. We have revealed a new anti-phase stripe superstructure in all the La-doped Bi2201 samples, giving rise to a new modulation with a vector q2. This q2 modulation is directly evolved from the orthogonal modulation q1 through an addition of the anti-phase structure so that its vector q2 is equal to q1b/2. We also discussed the implication of these structural studies on the electronic structure by angle-resolved photoemission spectroscopy (ARPES) experiments in La–Bi2201.

Structural domain walls in polar hexagonal manganites

The domain structure in the multiferroic hexagonal manganites, h-RMnO(3) (R=Sc, Y, Dy-Lu), is currently intensely investigated, motivated by the observation of nanoscale electrical conductivity at the domain walls and intriguing sixfold topological defects at their meeting points, as well as reports of coupling between ferroelectricity, magnetism and structural antiphase domains. The detailed structure of the domain walls, as well as the origin of such couplings, however, was previously unknown. Here we use first-principles electronic structure calculations to elucidate the structure and properties of the structural domain walls in the hexagonal manganites. Our results allow us to explain why ferroelectric domain walls are always simultaneously antiphase walls, propose a mechanism for ferroelectric switching through domain-wall motion, suggest a structure for the observed sixfold topological defects and predict a topological protection of experimentally observed stripe domains in hexagonal manganites.

Collective Magnetism at Multiferroic Vortex Domain Walls

Cross-coupled phenomena of multiferroic domains and domain walls are of fundamental scientific and technological interest. Using cryogenic magnetic force microscopy, we find alternating net magnetic moments at ferroelectric domain walls around vortex cores in multiferroic hexagonal ErMnO(3), which correlate with each other throughout the entire vortex network. This collective nature of domain wall magnetism originates from the uncompensated Er(3+) moments at domain walls and the self-organization of the vortex network. Our results demonstrate that the collective domain wall magnetism can be controlled by external magnetic fields and represent a major advancement in the manipulation of local magnetic moments by harnessing cross-coupled domain walls.

Doping Effect on Interlocked Ferroelectric and Structural Antiphase Domains in YMnO3

Changes in ferroelectric and structural antiphase domain structure by the partial substitution of nonmagnetic Ti4+ ions at the Mn site were investigated carefully by electron diffraction, dark-field imaging, and high-resolution lattice imaging experiments. The ferroelectric and structural antiphase domains are revealed to be mutually interlocked in YMnO3 and, on the other hand, when x was increased up to x∼0.30 in YMn1-xTixO3, the ferroelectric domains disappeared and the size of the structural antiphase domains decreased to approximately 10 nm at x∼0.30. High-resolution lattice images clearly demonstrate the coexisting state of nanodomains characterized by the modulated structure due to the structural trimerization and the nonmodulated structures. Our experimental results suggest that a partial substitution of Ti4+ ions suppressed the ferroelectric displacement along the [001] direction and the correlation length of the Mn3+ trimerization decreased.

Doping Effect on Interlocked Ferroelectric and Structural Antiphase Domains in YMnO3

Changes in ferroelectric and structural antiphase domain structure by the partial substitution of nonmagnetic Ti4+ ions at the Mn site were investigated carefully by electron diffraction, dark-field imaging, and high-resolution lattice imaging experiments. The ferroelectric and structural antiphase domains are revealed to be mutually interlocked in YMnO3 and, on the other hand, when x was increased up to x∼0.30 in YMn1-xTixO3, the ferroelectric domains disappeared and the size of the structural antiphase domains decreased to approximately 10 nm at x∼0.30. High-resolution lattice images clearly demonstrate the coexisting state of nanodomains characterized by the modulated structure due to the structural trimerization and the nonmodulated structures. Our experimental results suggest that a partial substitution of Ti4+ ions suppressed the ferroelectric displacement along the [001] direction and the correlation length of the Mn3+ trimerization decreased.