Inverse Structure Research Articles

Exploring the structural, magnetic, and dielectric properties of Fe and Y substituted NiCr2O4

This paper presents the successful single phase synthesis of NiCr2O4 and NiFe0.50Cr1.50-xYxO4 (x = 0 – 0.08) compounds followed by an investigation into their structural, magnetic and dielectric properties. The structural analysis confirms tetragonal structure for NiCr2O4 while a partially inverse cubic spinel structure for Fe and Y substituted samples (x = 0 – 0.08). Fe substitution (x = 0) induces a shift in room temperature hysteresis loop behaviour from paramagnetic to ferrimagnetic, suggesting enhanced superexchange interactions and a significant rise in magnetic transition temperature beyond room temperature. However, it is found that further inclusion of Y (x = 0.04 – 0.08) leads to a slight weakening of superexchange interactions. The saturation magnetization increases with Y substitution, while coercivity and magnetocrystalline anisotropy follows a decreasing trend. The complex impedance studies unveil a relaxation phenomenon and the dielectric constant is found to increase with the substitution of Fe and Y. Analysis of temperature dependent ac conductivity data and the frequency exponent profile suggests small polaron hopping as the predominant transport mechanism up to 380 K in NiCr2O4 and x = 0 samples, shifting to large polaron hopping beyond this temperature. In samples with x =0.04 and 0.06 the transport mechanism is found to follow the small polaron tunneling model. However, in the x = 0.08 sample, large polaron tunneling becomes predominant beyond 365 K.

Spin-anomalous-Hall unidirectional magnetoresistance in light-metal/ferromagnetic-metal bilayers

Nonreciprocal magnetotransport is one of the central topics in spintronics because of its importance for electrically probing magnetic information. Among numerous electrical probes used to read magnetic orders, unidirectional magnetoresistance (UMR), characterized by sign changes upon reversal of either current or magnetization, is currently a matter of great interest and has been identified in various spin–orbit-coupled bilayer systems composed of an (anti)ferromagnetic layer and a nonmagnetic layer with strong spin Hall effect. A recent theoretical work predicts that a spin-anomalous-Hall (SAH) UMR in those metallic conducting bilayers can originate from the spin-anomalous-Hall effect of the ferromagnetic layer and the structural inversion asymmetry. However, this type of UMR has not been reported experimentally. Here, we give the experimental evidence of spin-anomalous-Hall UMR in the light-metal/ferromagnetic-metal Cu/Co bilayers, where the emergence of net nonequilibrium spin density is attributed to the interfacial spin leakage asymmetry due to the spin memory loss effect at the Cu/Co interface and multiple spin reflections. We also show a highly tunable UMR in the Cu/Co/CuOx trilayer by varying the Cu thickness, which is due to the competition between the orbital Rashba effect in Co/CuOx and the spin-anomalous-Hall effect in Cu/Co. Our work widens the material choice for UMR device applications and provides an alternative approach to detect in-plane magnetization without an external spin polarizer.

Impact of carbon dots on the structural, morphological, magnetic, and electrochemical performance of Zn ferrite for energy storage applications

Magnetic core-shell Zn ferrite and carbon dots (C-dots) composite have been synthesized in this work using a simple coprecipitation and hydrothermal process, respectively. X-ray diffraction (XRD) patterns demonstrate an inverse spinel structure of Zn ferrites; the lattice parameter has decreased from 8.19 Å to 8.10 Å with C-dots. Scanning electron microscopy (SEM) images reveal rods-like structures for C-dots, and in the composite case, it is uniformly dispersed using low contrast consecutive C-dot layers to produce a core-shell structure. Zn ferrites are non-uniform in size, whereas C-dots and their composites are in uniform shape according to SEM images. The energy dispersive X-ray (EDX) study indicates that the substitution has been successful. For Zn ferrites, and composite, the Fourier transform infrared (FTIR) spectra shows that the absorption band of the tetrahedral site at 990 cm−1, and 870 cm−1, respectively. Different bonds in the infrared spectrum match specific function groups and bonding in various chemicals. The vibrating sample magnetometry (VSM) results indicates that the composite displays ferrimagnetic behavior. The specific capacity for composite has been found to be 2351 and 1790 F/g using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements, respectively. Higher electrochemical performance of the prepared composites may be helpful for energy storage systems.

Photocatalytic Degradation of Organic Dyes by Magnetite Nanoparticles Prepared by Co-Precipitation.

Iron oxide nanoparticles were synthesized by co-precipitation using three different iron salt stoichiometric mole ratios. Powder X-ray diffraction patterns revealed the inverse cubic spinel structure of magnetite iron oxide. Transmission electron microscopic images showed Fe3O4 nanoparticles with different shapes and average particle sizes of 5.48 nm for Fe3O4-1:2, 6.02 nm for Fe3O4-1.5:2, and 6.98 nm for Fe3O4-2:3 with an energy bandgap of 3.27 to 3.53 eV. The as-prepared Fe3O4 nanoparticles were used as photocatalysts to degrade brilliant green (BG), rhodamine B (RhB), indigo carmine (IC), and methyl red (MR) under visible light irradiation. The photocatalytic degradation efficiency of 80.4% was obtained from Fe3O4-1:2 for brilliant green, 61.5% from Fe3O4-1.5:2 for rhodamine B, and 77.9% and 73.9% from Fe3O4-2:3 for both indigo carmine and methyl red. This indicates that Fe3O4-2:3 is more efficient in the degradation of more than one dye. This study shows that brilliant green degrades most effectively at pH 9, rhodamine B degrades best at pH 6.5, and indigo carmine and methyl red degrade most efficiently at pH 3. Recyclability experiments showed that the Fe3O4 photocatalysts can be recycled four times and are photostable.

Optimum identification of aquifer parameter zone structures using the SHuffled Ant Lion Optimization approach considering general form of the Voronoi tessellation

A new simulation–optimization approach is proposed for solving the inverse parameter structure identification problems in groundwater systems. In the simulation part of the proposed approach, the numerical groundwater flow process is simulated by using MODFLOW. Parameter structures of the aquifer system are identified by partitioning the flow domain into a finite number of zones employing the general form of the Voronoi tessellation (VT). This MODFLOW and VT-based simulation model is then integrated into an optimization model where the SHuffled Ant Lion Optimization approach (SHALO) is used. This work is the first application of SHALO by considering the general form of the VT zonation approach for solving the inverse groundwater parameter structure identification problems. The applicability of the proposed simulation–optimization approach is evaluated on a hypothetical aquifer model in the literature. This evaluation is conducted by solving the same problem using Ant Lion Optimization (ALO) and its improved version, the self-adaptive ALO (saALO) for the same conditions. Furthermore, the identified results are compared with those obtained using harmony search (HS) and hybrid genetic algorithm (hybrid GA) based solution approaches in the literature. The obtained results indicated that the proposed approach provided better identification results than ALO, saALO, HS, and hybrid GA in terms of different evaluation metrics.

Directional HVSR at the Chalco lakebed zone of the Valley of Mexico: Analysis and interpretation

This study delves into Horizontal-to-Vertical Spectral Ratio (HVSR) and directional HVSR (D-HVSR) using continuous 30-min ambient seismic noise (ASN) signals recorded at 68 sites in the Chalco lakebed zone of the Valley of Mexico (VM). Our aim is to explore the shallow stratigraphy and subsurface structures in that zone. The isoperiod map using the HVSR, and the ensuing velocity structure inversion reveals a basin of irregular shape and shallow depth in the surroundings. Additionally, we explore azimuthal effects by computing the D-HVSR by rotating the records to obtain the time series for a given direction. We found different polarizations at the measurement points, and focused on the frequencies in which the effect is more pronounced. The cases with significant polarizations at the dominant frequencies suggest an irregularity at the basement level. This is supported by preliminary synthetic results that uses the three-dimensional (3D) Indirect Boundary Element Method (IBEM) to assess the effects of interface irregularities like a channel or dike. In the present stage of development, the D-HVSR is a powerful tool to reveal the existence of lateral variations. The complexity of the lakebed zone response in the VM and its irregular characteristics show the potential of the D-HVSR approach as well as the need to deeply explore into the modeling for its better understanding and interpretation.

Acoustic-assisted deposition of ordered self-assembled silica opal layers on hydrophilic single crystal diamond substrates

We deposited self-assembled films of a few monolayers of silica spheres from the water-based colloid on vertically moving hydrophilic single crystal diamond substrates. The use of acoustic agitation of the water suspension with the SiO2 nanospheres significantly improved the long-range order of the films with opal structure. The study examines the evolution of the structure, specifically the size of single crystal domains, with the assistance of sound frequency (0–2500 Hz) and intensity (0–125 dB). Optimal (resonance) parameters are determined based on scanning electron microscopy and optical reflection spectroscopy of the films. The production of high-quality photonic crystals, including templates for diamond-based ordered composites and inverse opal structures, is a promising application of acoustic crystallization of opals on diamond substrates.

High-Throughput Screening of All-d-Metal Heusler Alloys for Magnetocaloric Applications.

Due to their versatile composition and customizable properties, A2BC Heusler alloys have found applications in magnetic refrigeration, magnetic shape memory effects, permanent magnets, and spintronic devices. The discovery of all-d-metal Heusler alloys with improved mechanical properties compared to those containing main group elements presents an opportunity to engineer Heusler alloys for energy-related applications. Using high-throughput density-functional theory calculations, we screened magnetic all-d-metal Heusler compounds and identified 686 (meta)stable compounds. Our detailed analysis revealed that the inverse Heusler structure is preferred when the electronegativity difference between the A and B/C atoms is small, contrary to conventional Heusler alloys. Additionally, our calculations of Pugh ratios and Cauchy pressures demonstrated that ductile and metallic bonding are widespread in all-d-metal Heuslers, supporting their enhanced mechanical behavior. We identified 49 compounds with a double-well energy surface based on Bain path calculations and magnetic ground states, indicating their potential as candidates for magnetocaloric and shape memory applications. Furthermore, by calculating the free energies, we propose that 11 compounds exhibit structural phase transitions and suggest isostructural substitutions to enhance the magnetocaloric effect.

Phase Separation Derived Anisotropic Adhesive Structural Color Hydrogel Films For Flexible Electronics

AbstractHydrogels hold great promise in the field of flexible electronics. Attempts in this area tend to the microstructure design of hydrogels, giving them specific adhesion and multi‐sensing functions. Here, a novel phase separation‐derived anisotropic adhesive structural color hydrogel film is presented for visually flexible electronics. The hydrogel film is generated by template replicating colloidal crystal by using phase separation emulsions of hydrophilic monomer (acrylic acid, AA), hydrophobic monomer (lauryl methacrylate, LMA), co‐monomer ([2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide (SBMA)), surfactants (hexadecyl trimethyl ammonium bromide, CTAB) and initiator (ammonium persulphate (APS)). The appearance of phase separation results in asymmetric morphologies of hydrogel film, imparting them with anisotropic adhesive performance. Attributed to the formation of inverse opal scaffold structure, the hydrogel film is featured with vivid structural color, showing superior capability in self‐reporting mechanical behavior. Additionally, benefitting from the presence of abundant ions, the hydrogel film exhibits great conductivity. Thus, the resultant hydrogel film is demonstrated with stable dual‐signal sensing properties involving color‐changing and conductivity feedback ability to respond to human activities. These features make the proposed anisotropic adhesive structural color hydrogel film highly potential in the flexible electronic field.

Inverse design of crystals and quasicrystals in a non-additive binary mixture of hard disks.

The development of new materials typically involves a process of trial and error, guided by insights from past experimental and theoretical findings. The inverse design approach for soft-matter systems has the potential to optimize specific physical parameters, such as particle interactions, particle shape, or composition and packing fraction. This optimization aims to facilitate the spontaneous formation of specific target structures through self-assembly. In this study, we expand upon a recently introduced inverse design protocol for monodisperse systems to identify the required conditions and interactions for assembling crystal and quasicrystal phases within a binary mixture of two distinct species. This method utilizes an evolution algorithm to identify the optimal state point and interaction parameters, enabling the self-assembly of the desired structure. In addition, we employ a convolutional neural network (CNN) that classifies different phases based on their diffraction patterns, serving as a fitness function for the desired structure. Using our protocol, we successfully inverse design two-dimensional crystalline structures, including a hexagonal lattice and a dodecagonal quasicrystal, within a non-additive binary mixture of hard disks. Finally, we introduce a symmetry-based order parameter that leverages the encoded symmetry within the diffraction pattern. This order parameter circumvents the need for training a CNN and is used as a fitness function to inverse design an octagonal quasicrystal.

Effect of post-annealing on structural, optical and electrochemical properties of LiNiVO4 thin films deposited by spray pyrolysis technique

LiNiVO4 films were deposited by spray pyrolysis technique on flexible stainless steel as substrates. The XRD results confirm the formation of LiNiVO4 in a highly crystalline form with an inverse spinel structure after post-annealing the film at 600 °C. From the SEM analysis, it was found that increasing the annealing temperature resulted in the merging of grain boundaries which leads to the formation of larger grains. The bandgap was determined, demonstrating that higher annealing temperatures result in the decrement of bandgap from 2.52 to 2.38 eV. The electrochemical performance of the prepared films was studied using a three-electrode set-up. The LiNiVO4 film annealed at 600 °C exhibited a specific capacitance of 38 F/g at 0.1 A/g current density in 1 M LiOH as an electrolyte.

Symmetries and wave functions of photons confined in three-dimensional photonic band gap superlattices

We perform a computational study of confined photonic states that appear in a three-dimensional (3D) superlattice of coupled cavities, resulting from a superstructure of intentional defects. The states are isolated from the vacuum by a 3D photonic band gap, using a diamondlike inverse woodpile crystal structure, and they exhibit “Cartesian” hopping of photons in high-symmetry directions. We investigate the confinement dimensionality to verify which states are fully 3D-confined, using a recently developed scaling theory to analyze the influence of the structural parameters of the 3D crystal. We create confinement maps that trace the frequencies of 3D-confined bands for select combinations of key structural parameters, namely the pore radii of the underlying regular crystal and of the defect pores. We find that a certain minimum difference between the regular and defect pore radii is necessary for 3D-confined bands to appear, and that an increasing difference between the defect pore radii from the regular radii supports more 3D-confined bands. In our analysis, we find that their symmetries and spatial distributions are more varied than electronic orbitals known from solid-state physics. We surmise that this difference occurs since the confined photonic orbitals derive from global Bloch states governed by the underlying superlattice structure, whereas single-atom orbitals are localized. Based on this realization, we suggest that the extent symmetries of “photonic orbitals” could possibly translate to novel macroscopic behaviors of “photonic solid-state matter,” never before seen in the standard electronic solid-state systems. We also discover pairs of degenerate 3D-confined bands with p-like orbital shapes and mirror symmetries matching the symmetry of the superlattice. Finally, we investigate the enhancement of the local density of optical states for cavity quantum electrodynamics applications. We find that donorlike superlattices, i.e., where the defect pores are smaller than the regular pores, provide greater enhancement in the air region than acceptorlike structures with larger defect pores, and thus offer better prospects for doping with quantum dots and ultimately for 3D networks of single photons steered across strongly coupled cavities. Published by the American Physical Society 2024

Precision prediction in grinding processes based on displacement signal conversion into recurrent plot

The processing of grinding data and the prediction of accuracy are extremely complex; this paper proposes a novel prediction method to ensure the machining accuracy of computer numerical control (CNC) grinding machines. It consists of two components, namely the filter decomposition recurrence plot (RP) transformation (FDRP) and the deep inverted residual attention network (DIRAN). A pipeline named FDRP has been designed to address the issues in the processing of data and the shortcomings of RP. Firstly, the displacement signals undergo filtering to preserve essential grinding information while effectively removing noise. Secondly, long-time series signals are decomposed and augmented based on the characteristics of the machining process. Lastly, an RP transformation is applied to one-dimensional time series data, resulting in the generation of images that accurately represent the grinding process. Furthermore, this paper proposes a novel machining accuracy prediction model. The DIRAN uses a multi-layer inverse residual network structure combined with attention mechanism to extract the features of two-dimensional RP, and its performance is better than other typical prediction methods. It can be applied to predict the polar angle of the workpiece in industrial processing and reduce the defect rate.

Investigation on the failure mechanism of the internal erosion in inverse grading sand based on DDA and Darcy’s law

Inverse grading structures are commonly found in landslide accumulations of high-speed and long-runout landslides. However, there is limited research on the internal erosion of inverse grading deposits. This study developed a program called discontinuous deformation analysis (DDA) and Darcy’s law coupling program (DDCP) using C language to investigate the failure mechanism associated with internal erosion in inverse grading sand. The results indicate that as the hydraulic gradient increases, the internal erosion phenomenon becomes more pronounced. The failure of the inverse grading sand due to internal erosion can be attributed to three processes: loss of fine particles in the lower layer, accumulation of the particles from the upper layer in the lower layer, and flow of fine particles from the upper layer through the lower layer and exit from the bottom. During the internal erosion process, both the hydraulic conductivity and porosity initially decrease and then increase. Similarly, the average velocity of fine particles exceeds that of coarse particles in each layer. The stability of the inverse grading sand during the internal erosion increases with a higher content of fine particles in the lower layer. These findings are significant in understanding the mechanism of internal erosion within inverse grading deposits.

Tuning Displacement Fields in a Two-Dimensional Topological Insulator Using Nanopatterned Gates.

Epitaxial heterostructures with topological insulators enable novel quantum phases and practical device applications. Their topological electronic states are sensitive to the microscopic parameters, including structural inversion asymmetry (SIA), which is an inherent feature of many real heterostructures. Controlling SIA is challenging, because it requires the ability to tune the displacement field across the topological film. Here, using nanopatterned gates, we demonstrate a tunable displacement field in a heterostructure of the two-dimensional topological insulator cadmium arsenide. Transport studies in magnetic fields reveal an extreme sensitivity of the band inversion to SIA. We show that a relatively small displacement field (∼50 mV/nm) converts the crossing of the two zeroth Landau levels in magnetic field to an avoided crossing, signaling a change to trivial band order. This work demonstrates a universal methodology for tuning electronic states in topological thin films.

Enhancement the electrical and linear/nonlinear optical properties of ZnCo2O4 through Al3+doping

In this work, ZnCo2O4 samples doped with Al3+ were prepared by the hydrothermal method. Synchrotron x-ray diffraction, FTIR, SEM and EDX techniques were used to investigate the structure, microstructure, morphology, and composition of ZnCo2-xAlxO4 samples. Rietveld analysis revealed a nearly inverse structure for the undoped ZnCo2O4. The degree of inversion is increased upon increasing the Al3+ doping content. Al ions preferentially occupy the octahedral B-site. The optical band gaps of ZnCo2−xAlxO4 samples are 1.9, 1.8 and 1.91 eV for x = 0, 0.1 and 0.2, respectively. Different empirical models were used to obtain the refractive index of the different samples using their corresponding optical band gaps. The increase in non-linear optical values in the sample with x = 0.1 suggested that this sample could be used in a variety of photonic applications. The effects of frequency and temperature on the dielectric permittivity, impedance and electrical modulus of different samples were explored. All samples exhibited the non-Debye relaxation phenomenon. The relaxation time of each sample is affected with the frequency and temperature. The Cole-Cole curve is employed to reduce uncertainty regarding the electrical characteristics of these ZnCo2−xAlxO4 samples induced by grain boundaries or bulk grain. The substitution of Al3+ ions can regulate the conductivity of the ZnCo2O4 sample.

A method for non-linear inversion of the stellar structure applied to gravity-mode pulsators

We present a method for a non-linear asteroseismic inversion suitable for gravity-mode pulsators and apply it to slowly pulsating B-type (SPB) stars. Our inversion method is based on the iterative improvement of a parameterised static stellar structure model, which in turn is based on constraints from the observed oscillation periods. We present tests to demonstrate that the method is successful in recovering the properties of artificial targets both inside and outside the parameter space. We also present a test of our method on the well-studied SPB star KIC 7760680. We believe that this method is promising for carrying out detailed analyses of observations of SPB and γ Dor stars and will provide complementary information to evolutionary models.

The synthesis of Fe3O4@SiO2 superparamagnetic materials and mechanism of catalysis

Abstract The superparamagnetic Fe3O4 was fabricated by the solvothermal synthesis, in which medium ferric chloride is the iron source and deoxidizer using as ethylene glycol. The core-shell material Fe3O4@SiO2 was fabricated by the scheme which was composed of Anhydrous ethanol, deionized water, ammonia water, and tetraethyl orthosilicate (TEOS). The structural and optical characteristics of the samples Fe3O4 and core-shell Fe3O4@SiO2 was detected by X-ray diffraction (XRD), transmission electron microscope (TEM), Vibrating sample magnetometer (VSM), and UV/VIS/IR spectrophotometer. The conclusions illustrate that the spherical core-shell structure of Fe3O4 and Fe3O4@SiO2 were fabricated with superparamagnetic. The Ostwald ripening effect on structure of sample Fe3O4 was concluded to form inverse spinel polycrystal structure by nanometer particles. The visual-driven photocatalytic properties of Fe3O4 and Fe3O4@SiO2 nanoparticles toward the deposition of methodology blue was studied. The obtained conclusions indicate that Fe3O4@SiO2 after irradiated by visible light, its degradation rate of methodology methylene mlue (MB) was enhanced than Fe3O4 in the presence of H2O2. The samples Fe3O4 and core-shell Fe3O4@SiO2 materials are recycled by external magnetic field and reused for special superparamagnetic property. The sample Fe3O4 and core-shell Fe3O4@SiO2 materials represent higher catalytic property and excellent fixity consistent with the decomposition rate of methodology methylene mlue (MB) after being recycling and reuse severe times. The photocatalytic mechanism was dismissed based on the determined active agent during the process of degraded wastewater.

Unified model modal expansion method for full field reconstruction and inversion under mechanical and thermal loading

In this paper, a novel method termed UMM-T&S (Unified Model Modal reconstruction and inversion method for Temperature field and Structural field under limited sensors) is proposed. This method aims to enhance high-precision structural performance inversion and reconstruction under mechanical and thermal loading conditions, particularly in the context of structural health monitoring within the aviation and aerospace sectors. The approach begins by deriving the “temperature modal” solution of the heat conduction equation, drawing upon the modal expansion techniques used in multi-degree-of-freedom systems. This is followed by constructing a parameter mapping relationship within the unified model, enabling the solution of both the structural field (encompassing strain and displacement) and the temperature field through a single structural model modal expansion. Furthermore, the paper details a numerical validation using two different temperature fields and a thermal loading experimental verification on a stiffened plate under five distinct working conditions. The proposed UMM-T&S method yields lower errors (ranging between 10%-40%) and more stable performance across various complex working conditions, in comparison to existing methods. The analysis also delves into the sources of errors and their cumulative impacts.In conclusion, the innovative UMM-T&S method offers a swift, precise, and robust solution for the intricate task of reconstructing and inverting structural performance under combined mechanical and thermal stresses. The method's efficacy and potential are substantiated through experimental validation and comparative analysis against an established methodology, underscoring its capability to effectively tackle the challenges faced in structural monitoring under such demanding conditions.

Synthesis of novel iron Oxide/Carbon dots green nanocomposites for bacteria detection and antibacterial agent applications

Due to the widespread of pathogens and infectious diseases, rapid detection and antibacterial agents are needed. Antibacterial nanomaterials have attracted attention due to their advantageous properties and unique mechanisms. Besides, the green route approach to synthesizing nanoparticles has attracted interest due to being environmentally friendly, biocompatible, and non-toxic. In this study, carbon dots (Cdots), a promising antibacterial material, have been combined with the Fe3O4 nanoparticles as the carrier and produce Fe3O4/Cdots nanocomposite via green synthesis for bacteria detection and antibacterial agents. Green synthesis was achieved with Moringa oleifera leaves extract as reducing agent on Fe3O4 and watermelon peel as carbon source on Cdots. X-ray diffraction shows a cubic inverse spinel structure of magnetite. The phase composition of the nanocomposites consists of magnetite and carbon. The particle size of nanocomposites is 13.4 nm with semi-spherical morphology and high surface area. The bonding analysis and element composition are consistent with phase composition estimation that confirms the existence of Fe3O4 and Cdots on the nanocomposites and lacks other impurities. The vibrating sample magnetometer shows the superparamagnetic behavior of the samples. Nanocomposites were used to detect Escherichia coli (E. coli) bacteria. The quenching of photoluminescence of the nanocomposite shows an increase in the amount of E. coli bacteria. Furthermore, nanocomposites produce high inhibition zones against E. coli bacteria within 48 h, offering excellent antibacterial properties. Hence, nanocomposites provide a promising agent for bacteria detection and antibacterial treatment.