Role Of Anisotropy Research Articles

Exploring spin squeezing in the Mott insulating regime: Role of anisotropy, inhomogeneity, and hole doping

Exploring spin squeezing in the Mott insulating regime: Role of anisotropy, inhomogeneity, and hole doping

Controlled Self-Assembly of Nanoscale Superstructures in Phase-Change Ge-Sb-Te Nanowires.

Controlled growth of semiconductor nanowires with atomic precision offers the potential to tune the material properties for integration into scalable functional devices. Despite significant progress in understanding the nanowire growth mechanism, definitive control over atomic positions of its constituents, structure, and morphology via self-assembly remains challenging. Here, we demonstrate an exquisite control over synthesis of cation-ordered nanoscale superstructures in Ge-Sb-Te nanowires with the ability to deterministically vary the nanowire growth direction, crystal facets, and periodicity of cation ordering by tuning the relative precursor flux during synthesis. Furthermore, the role of anisotropy on material properties in cation-ordered nanowire superstructures is illustrated by fabricating phase-change memory (PCM) devices, which show significantly different growth direction dependent amorphization current density. This level of control in synthesizing chemically ordered nanoscale superstructures holds potential to precisely modulate fundamental material properties such as the electronic and thermal transport, which may have implications for PCM, thermoelectrics, and other nanoelectronic devices.

Microstructural Influence on Fracture Toughness of IF Steel and DP Steel

Interstitial free steels (IF) and Dual-phase (DP) steels are widely used in the automotive industry, their specific application is driven by requirements to optimize the strength-to-weight ratio. Utilizing the full capacity of their plasticity and strain hardenability requires an assessment of edge fracture susceptibility and flangeability. In this work, the ability of the mentioned steels to spreading of deformation along initiated cracks is evaluated by structural and fractographic analyzes. Microstructural restrictions of plasticity are correlated with fracture toughness results, adopting the essential work of fracture (EWF) methodology. Crystallographic analyzes (EBSD) are focused on the role of anisotropy and the deformation texture evolution, affecting the development of plasticity and thus the energy consumption to the fracture.

Role of anisotropy on topological structures of elasticity, anisotropy, brittleness and phonon in Al3Ti

Based on tensor theory and Bond matrix model, the anisotropy, brittleness/plasticity, and stress–strain under bulk and point stresses are systematically studied, in order to find the effect of anisotropy on their structures. The applications of the Kelvin-Christoffel tensor are mainly focused on phonon focusing and phonon image with Gaussian curvature method. The investigation of phonon entropy shows that the 3-branche lattice waves are mainly composed of long acoustic waves and long optical waves. The slowness of the three lattice waves is influenced by anisotropy as follows: the slow shear wave is the largest, the fast shear wave is the second, and the longitudinal wave is the smallest. This is well explained by the 3D anisotropy of phonon amplification coefficients.PACS: 62.20.D-; 74.25.Ld; 62.30. +d; 63.20.-e; 74.25.Ld; 94.20.Bb

Role of magnetoelastic coupling and magnetic anisotropy in MnTiO3

We report the thermodynamic properties studied by thermal expansion, magnetostriction, magnetisation, and specific heat measurements as well as the low-energy magnetic excitations of \mto\ and investigate how magneto-elastic coupling and magnetic anisotropy affect the evolution of long-range order and the magnetic phase diagram. Specifically, we utilise high-resolution capacitance dilatometry and antiferromagnetic resonance (AFMR) studies by means of high-frequency electron spin resonance (HF-ESR) spectroscopy. The role of anisotropy is reflected by spin-reorientation at $B_{\rm{SF}}$~$\simeq 6$~T and a corresponding sign change in $\partial T_{\rm N}/\partial B$. Analysis of the AFMR modes enables us to establish the zero-field excitation gap $\Delta$ as well as its temperature dependence. We derive the effective anisotropy field $B_\mathrm{A} = 0.16(1)$~T which predominately originates from out-of-plane nearest-neighbour dipole-dipole interactions. Despite the nearly fully quenched orbital moment, our data show pronounced thermal expansion and magnetostriction anomalies at $T_{\rm N}$ and $B_{\rm{SF}}$ , respectively, which allows the experimental determination of sizable uniaxial pressure dependencies, i.e., $\partial B_{\rm SF}/\partial p_{\rm c} = -0.20(2)$~T/GPa, $\partial T_{\rm N}/ \partial p_b = 0.69(12)$~K/GPa, and $\partial T_{\rm N}/ \partial p_c = -2.0(4)$~K/GPa. Notably, short-range magnetic order appears up to at least 3$T_{\rm N}$ , as indicated by anisotropic lattice distortion, the violation of a constant Gr\"uneisen behavior, and the presence of local magnetic fields detected by HF-ESR.

An Eulerian crystal plasticity framework for modeling large anisotropic deformations in energetic materials under shocks

This paper demonstrates a novel Eulerian computational framework for modeling anisotropic elastoplastic deformations of organic crystalline energetic materials (EM) under shocks. While Eulerian formulations are advantageous for handling large deformations, constitutive laws in such formulations have been limited to isotropic elastoplastic models, which may not fully capture the shock response of crystalline EM. The present Eulerian framework for high-strain rates, large deformation material dynamics of EM incorporates anisotropic isochoric elasticity via a hypo-elastic constitutive law and visco-plastic single-crystal models. The calculations are validated against atomistic calculations and experimental data and benchmarked against Lagrangian (finite element) crystal plasticity computations for shock-propagation in a monoclinic organic crystal, octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (β-HMX). The Cauchy stress components and the resolved shear stresses calculated using the present Eulerian approach are shown to be in good agreement with the Lagrangian computations for different crystal orientations. The Eulerian framework is then used for computations of shock-induced inert void collapse in β-HMX to study the effects of crystal orientations on hotspot formation under different loading intensities. The computations show that the hotspot temperature distributions and the collapse profiles are sensitive to the crystal orientations at lower impact velocities (viz., 500 m/s); when the impact velocity is increased to 1000 m/s, the collapse is predominantly hydrodynamic and the role of anisotropy is modest. The present methodology will be useful to simulate energy localization in shocked porous energetic material microstructures and other situations where large deformations of single and polycrystals govern the thermomechanical response.

Role of anisotropy on strain localization at high-strain rates in Ti6Al4V

A systematic experimental investigation of the plastic anisotropy at high strain-rates of Ti6Al4V was carried out using a Split Hopkinson bar system. Dynamic tensile tests were conducted on flat specimens cut at seven orientations with respect to the rolling direction of the sheet. To quantify the effect of anisotropy on both the global response prior to necking as well as on the inclination of the strain localization bands that developed in the neck, both surface strains and local displacements were measured using high speed imaging in conjunction with digital image correlation. It was found that the material has a weak anisotropy in uniaxial yield stresses while it displays a strong anisotropy in Lankford coefficients; the inclinations of the bands in the neck depend on the loading orientation. Moreover, only for the rolling direction specimen, the neck contains two localization bands equally inclined to the loading axis. These observations confirm the correlations established in the theoretical study of Cazacu and Rodríguez-Martínez (2019) between the necking band angles and the variation in the uniaxial flow stresses with the loading direction. A constitutive model with yielding described with the orthotropic criterion of Cazacu and Barlat (2001) and a hardening law accounting for the strain rate effects was used to model the observed behavior. Comparison between finite element simulations, analytical calculations, and test data show that the experimental trends are captured.

Optical Properties of Inorganic Halide Perovskite Nanorods: Role of Anisotropy, Temperature, Pressure, and Nonlinearity

Optical Properties of Inorganic Halide Perovskite Nanorods: Role of Anisotropy, Temperature, Pressure, and Nonlinearity

Role of Anisotropy on Topological Structures of Elasticity, Anisotropy, Brittleness and Phonon in Al3ti

Role of Anisotropy on Topological Structures of Elasticity, Anisotropy, Brittleness and Phonon in Al3ti

Simulation of the time-dependent behaviour of a test embankment on soft soil

The now-abandoned project for a new international airport for Mexico City was located at a site on the former Texcoco Lake, where extremely difficult subsoil conditions prevail. The behaviour of one of the trial embankments built to test foundation solutions for the runways is analysed in this paper. Observational data were gathered over 50 months at the so-called reference embankment, where no special foundation or soil improvement techniques were adopted. The performance of this embankment was investigated through finite-element simulations in which an elasto-viscoplastic constitutive model was implemented in commercial software. The model incorporates key features such as time dependence, long-term deformation and an anisotropic flow surface. The results provide an assessment of the constitutive description adopted as well as the role of anisotropy in the simulation of the case study.

Role of anisotropy in elastographic tissue characterization

The structure and function of soft tissues are intimately connected. Some soft tissues are organized in such a way that they have material properties that are anisotropic, that is, the measured properties depend on which direction they are measured. Some such tissues are the brain, kidney, arteries, and cardiac and skeletal muscle. We will provide a brief overview of work targeted at characterization of the anisotropic mechanical properties in kidney and cardiac and skeletal muscles. In many cases, these tissues can be assumed to be transversely isotropic, which allows for simplification in estimating their mechanical properties. The use of propagating shear waves can be used to determine these mechanical properties. As a comparison example, we will show data from characterization of renal tissue with ultrasound shear wave elastography (SWE) and optical coherence elastography. We will also provide an overview of evaluation of skeletal muscle mechanical properties using shear wave elastography techniques and use of model fitting to estimate mechanical properties. Special care must be taken in evaluation of such anisotropic tissues to ensure that measurements are standardized across practices and studies.

Role of anisotropy in the ballistic response of rolled magnesium

Rolled magnesium alloys exhibit pronounced tension-compression asymmetry as well as anisotropy in yield and strain-hardening behavior. Although differences in the mechanical response are reasonably well-understood, it is not clear to what extent anisotropy alters the deformation and failure of plates subjected to ballistic loading conditions. In this work, the role of texture and anisotropy in the ballistic response is investigated using a combined experimental–computational approach. Sphere impact experiments are performed on rolled magnesium plates cut from orientations that exhibit differing mechanical responses. The complex failure process is characterized by in situ diagnostics, including ultra-high-speed Digital Image Correlation and Photonic Doppler Velocimetry, and compared with simulations performed on polycrystalline aggregates using a polycrystal plasticity model for hcp metals. The anisotropic deformation behavior arises from deformation mechanisms with disparate strength and strain hardening behavior, which is well captured in the model. The occurrence of low-strength extension twinning is shown to govern the initial anisotropic deformation and bulging of the plate. When compared with post-mortem 3D X-ray microscopy, regions that experience intense basal slip are shown to be sites for damage initiation that leads to eventual fracture. The combination of experiments and simulations suggest that at low to intermediate ballistic loading rates, material orientation plays a crucial role in dictating eventual fracture and failure in strongly anisotropic metals such as in rolled magnesium alloys.

On a phase-field approach to model fracture of small intestine walls

We address anisotropic elasticity and fracture in small intestine walls (SIWs) with both experimental and computational methods. Uniaxial tension experiments are performed on porcine SIW samples with varying alignments and quantify their nonlinear elastic anisotropic behavior. Fracture experiments on notched SIW strips reveal a high sensitivity of the crack propagation direction and the failure stress on the tissue orientation. From a modeling point of view, the observed anisotropic elastic response is studied with a continuum mechanical model stemming from a strain energy density with a neo-Hookean component and an anisotropic component with four families of fibers. Fracture is addressed with the phase-field approach, featuring two-fold anisotropy in the fracture toughness. Elastic and fracture model parameters are calibrated based on the experimental data, using the maximum and minimum limits of the experimental stress-stretch data set. A very good agreement between experimental data and computational results is obtained, the role of anisotropy being effectively captured by the proposed model in both the elastic and the fracture behavior. Statement of significanceThis article reports a comprehensive experimental data set on the mechanical failure behavior of small intestinal tissue, and presents the corresponding protocols for preparing and testing the samples. On the one hand, the results of this study contribute to the understanding of small intestine mechanics and thus to understanding of load transfer mechanisms inside the tissue. On the other hand, these results are used as input for a phase-field modelling approach, presented in this article. The presented model can reproduce the mechanical failure behavior of the small intestine in an excellent way and is thus a promising tool for the future mechanical description of diseased small intestinal tissue.

Transient Cooling and Heating Effects in Holey Silicon-Based Lateral Thermoelectric Devices for Hot Spot Thermal Management

Lateral thermoelectric devices, where the Peltier cooling and heating occur in a lateral direction, have shown promise for thermal management of on-chip hot spots, and because of the device orientation, thermoelectric materials with anisotropic properties such as holey silicon have shown even more promising cooling potential. However, the role of anisotropy in transient cooling and heating effects is little known, and thermal management optimization using a pulse has not been considered with anisotropic materials. Here, we study temporal and spatial interplays of Peltier, Joule, and Thomson effects in a holey silicon-based lateral thermoelectric device with varying pulse conditions and material properties. Our simulations show a supercooling effect, driven by Peltier cooling before Joule heating diffuses in, and that holey silicon with anisotropic thermal conductivities is favorable by delaying the diffusion in the lateral direction while allowing rapid heat dissipation in the vertical direction. Depending on the local temperature distribution, the Thomson effect is shown to strengthen the supercooling effect. A holey silicon-based thermoelectric device with a 1 kW · cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> hot spot shows temperature reductions from 117 °C to 102 °C in steady-state and temporarily to 100 °C with optimal pulse conditions. The transient cooling performance can be further improved by incorporating phase-change materials within holey silicon, in which their melting process delays a temperature overshoot. The anisotropy, specific heat, and latent heat play important roles in determining the transient cooling performance. Our findings show that lateral thermoelectric devices with anisotropic properties are promising for dynamic thermal management of on-chip hot spots.

The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications.

Magnetic inductive heating (MIH) has been a topic of great interest because of its potential applications, especially in biomedicine. In this paper, the parameters characteristic for magnetic inductive heating power including maximum specific loss power (SLPmax), optimal nanoparticle diameter (Dc) and its width (ΔDc) are considered as being dependent on magnetic nanoparticle anisotropy (K). The calculated results suggest 3 different Néel-domination (N), overlapped Néel/Brownian (NB), and Brownian-domination (B) regions. The transition from NB- to B-region changes abruptly around critical anisotropy Kc. For magnetic nanoparticles with low K (K < Kc), the feature of SLP peaks is determined by a high value of Dc and small ΔDc while those of the high K (K > Kc) are opposite. The decreases of the SLPmax when increasing polydispersity and viscosity are characterized by different rates of d(SLPmax)/dσ and d(SLPmax)/dη depending on each domination region. The critical anisotropy Kc varies with the frequency of an alternating magnetic field. A possibility to improve heating power via increasing anisotropy is analyzed and deduced for Fe3O4 magnetic nanoparticles. For MIH application, the monodispersity requirement for magnetic nanoparticles in the B-region is less stringent, while materials in the N- and/or NB-regions are much more favorable in high viscous media. Experimental results on viscosity dependence of SLP for CoFe2O4 and MnFe2O4 ferrofluids are in good agreement with the calculations. These results indicated that magnetic nanoparticles in the N- and/or NB-regions are in general better for application in elevated viscosity media.

Implied models approach for turbulence model form physics-based uncertainty quantification

A new physics-based uncertainty quantification methodology is developed for understanding model form uncertainty. This framework provides insights into the reasons and conditions under which model assumptions are wrong and is used to study model form uncertainty in two-equation Reynolds-Averaged Navier-Stokes turbulence models in wall-bounded flows. Through this analysis, the shortcomings of these models are understood with an emphasis on the role of anisotropy. Error cancellation is shown to largely benefit two-equation turbulence models in wall-bounded flows, leading to models that provide correct predictions but lack physical correctness.

Role of Anisotropy, Frequency, and Interactions in Magnetic Hyperthermia Applications: Noninteracting Nanoparticles and Linear Chain Arrangements

Efforts by numerous research groups have provided a deeper insight into the physical mechanisms behind the power absorption of single-domain magnetic nanoparticles in magnetic-fluid-hyperthermia applications and theoretical models now account for the main experimental observations. However, the role of all parameters relevant to the magnetic relaxation remains a matter of debate. Here, we employ a nonlinear model for the magnetic relaxation of single-domain magnetic nanoparticles with uniaxial effective anisotropy and evaluate the influence of particle-intrinsic parameters as well as experimental conditions on the power absorption of both noninteracting and interacting systems (linear arrangements). These effects are assessed through the enclosed hysteresis area of the magnetization loops as a function of relative anisotropy ${h}_{K}$ (the anisotropy field with respect to the amplitude of the ac field), i.e., the ``area curve'' of the system. These curves can be divided into four regions with distinct magnetic responses and boundaries that depend on the particle size, frequency of the applied field and interactions. Interactions change the effective anisotropy of the system and shift the area curve towards lower ${h}_{K}$ values. For the low relative anisotropy range, dipolar interactions increase the area of the hysteresis loops [thus, the specific power absorption (SPA)], while they are detrimental or produce nonsignificant effects for the range of high relative anisotropy. Our study resolves seemingly contradictory results of interaction effects in linear arrangements recently reported in the literature. Simulations of randomly oriented particles and chains were contrasted with the oriented cases. An analytical approach and the thermal interpretation of its validity range are discussed, both aimed at the design of nanoparticles and the choice of the experimental conditions for optimal heating. We find that systems with low-thermal-fluctuation influence are better candidates for the application due to their high SPA values.

The Interaction between Surface Acoustic Waves and Spin Waves: The Role of Anisotropy and Spatial Profiles of the Modes.

The interaction between different types of wave excitation in hybrid systems is usually anisotropic. Magnetoelastic coupling between surface acoustic waves and spin waves strongly depends on the direction of the external magnetic field. However, in the present study we observe that even if the orientation of the field is supportive for the coupling, the magnetoelastic interaction can be significantly reduced for surface acoustic waves with a particular profile in the direction normal to the surface at distances much smaller than the wavelength. We use Brillouin light scattering for the investigation of thermally excited phonons and magnons in a magnetostrictive CoFeB/Au multilayer deposited on a Si substrate. The experimental data are interpreted on the basis of a linearized model of interaction between surface acoustic waves and spin waves.

Influence of aggregate geometry and material fabric on tensile cracking in concrete

A recently developed discrete element capability is used to understand the effect of random variations in aggregate shape and size on tensile cracking in concrete. A procedure to reconstruct the three-dimensional crack surface, and characterize its tortuosity, is proposed. The role of anisotropy in the material fabric, induced by variations in aggregate shape, is studied. Both tensile and compressive strength are seen to be affected by fabric anisotropy, but to different extents and in different ways. Post-peak behaviour in tension is linked to dispersion in the local fabric, characterized by a proposed local fabric tensor. The influence of aggregate shape on fracture process zone geometry is investigated. Overall, aggregate shape appears to be the dominant factor in determining the post-peak response. However aggregate size appears to affect the tensile strength more strongly while its influence on the fracture energy is complicated and subject to two opposing trends.

Quantum floquet oscillation in borophane

The hydrogenated borophene is known as borophane, a two-dimensional material which has Dirac characteristics. In this work, it is described how anisotropy of borophane, i.e. wave vector angle, plays a significant role in the Floquet frequency and collapse–revival phenomenon. The various mathematical techniques have been described for the formulation of Floquet frequency. The role of anisotropy is justified by using numerical simulation. The bandgap of borophane can be opened by using Floquet frequency. The Rabi oscillation and Bloch–Siegert shift have also been studied in the perspective of anisotropy.