Hysteresis Research Articles

Deciphering the structural, morphological, and electrical properties of rare-earth incorporated barium stannate titanate dielectric material

The primary aim of the current research is to explore the impact of yttrium-doping in barium stannate titanate (Ba[Formula: see text]YxTi[Formula: see text]SnzO3) to investigate the variation in its structural and electrical properties. The specimens were synthesized using a solid-state method, wherein the precursors were heated together until they reacted to form the desired compounds. Subsequently, X-ray diffractometric analysis was employed to confirm the crystallographic phases. Archimedes’ method was used to determine the density of the material. An Electron Paramagnetic Resonance (EPR) study was conducted to examine the nature of defect centers and impurity ions within the synthesized ceramics. Furthermore, the impact of yttrium (Y) substitution on the system’s morphology and grain growth was evaluated through SEM micrographs. Selective compositions were found with enhanced dielectric properties of barium titanate ceramic, exhibiting a dielectric constant of 9816 at the transition point. The highest value among all studied samples had a clear indication of DC conductivity. Piezoelectric coefficient (d[Formula: see text]) and P-E hysteresis loops were also investigated for these samples, indicating potential applications in electronic devices for the modified material’s improved ferroelectric properties.

Polytype switching by super-lubricant van der Waals cavity arrays.

Expanding the performance of field-effect devices is a key challenge of the ever-growing chip industry at the core of current technologies1. Non-volatile multiferroic transistors that control atomic movements rather than purely electronic distribution are highly desired2. Recently, a field-effect control over structural transitions was achieved in commensurate stacking configurations of honeycomb van der Waals (vdW) polytypes by sliding boundary strips between oppositely polarized domains3-6. This ferroelectric hysteretic response, however, relied on pre-existing dislocation strips between relatively large micron-scale domains, severely limiting practical implementations3,7,8. Here we report the robust electric switching of single-domain polytypes in nanometre-scale islands embedded in super-lubricant vdW arrays. We etch cavities into a thin layered spacer and then encapsulate it with functional flakes. The flakes above/under the lattice-mismatched spacer sag and touch at each cavity to form islands of commensurate and metastable polytype configurations. By imaging the polarization of the polytypes, we observe nucleation and annihilation of boundary strips and geometry-adaptable ferroelectric hysteresis loops. Using mechanical stress, we further control the position of boundary strips, modify marginal twist angles and nucleate patterns of polar domain. This super-lubricant arrays of polytype (SLAP) concept suggests 'slidetronics' device applications such as elastic-coupled neuromorphic memory cells and non-volatile multiferroic tunnelling transistors and programmable response by designing the size, shape and symmetry of the islands and of the arrays9.

Investigating the effect of termination capacitor on E–H mode transition in radio frequency inductively coupled plasma

In this work, the effects of stringing termination capacitors on the external circuit parameters, plasma parameters, and mode transition in radio frequency (RF) inductively coupled Ar discharges are investigated. It has been demonstrated that at low pressure (1 Pa), in the absence of termination capacitors, the plasma parameters and external circuit parameters exhibit a continuous variation with increasing RF power. The plasma density is observed to decrease with decreasing capacitance value in the E mode when the termination capacitor is inserted, while the plasma density is increased with decreasing capacitance value in the H mode. During the E–H mode transition process, both the plasma parameters and the external circuit parameters undergo a discontinuous change characterized by a distinct “jump” in each parameter. By increasing and then decreasing RF power, the evolution of each parameter creates a significant hysteresis. As the termination capacitance decreases, the power threshold of the H–E mode transition decreases, resulting in a larger hysteresis loop. The termination capacitor, which is connected in series at the end of the coil, can alter the voltage distribution on the RF antenna. This alteration results in a reduction in the potential difference between the coil and the “common ground,” which effectively diminishes the electrostatic field. Furthermore, the electron energy probability function indicates that the addition of the termination capacitor results in a reduction in the proportion of energetic electrons in the E mode, accompanied by a reduction in the plasma potential.

Influence of Interface Mixed Layer on Non-Collinear Exchange Coupling in V-Fe Multilayers

V/Fe multilayers were prepared on naturally oxidized Si(100) substrates at room temperature (RT) by UHV magnetron sputtering. Mixing effects at the Fe–V interfaces were investigated in-situ, directly after deposition, by means of X-ray photoelectron spectroscopy (XPS). The results of systematic in-situ XPS studies of the integral intensity of the Fe-2p peak, as a function of the nominal thickness of the Fe sublayer deposited on vanadium, allowed us to estimate the thickness of the pure iron layer that forms the mixed layer at about 0.4 nm. Assuming the same thickness of the vanadium layer that forms the mixed layer, the estimated thickness of the mixed layer near the Fe–V interface was about 0.8 nm. In the analysis of magnetic hysteresis loops, in addition to the bilinear (J1) and biquadratic (J2) coupling constant, the contribution of the cubic exchange constant (J3) was taken into account, which also contributed significantly to the total energy. Higher order interactions (J2 and J3) are particularly important for V spacer thicknesses greater than 7 atomic monolayers. Hydrogen absorption in V/Fe multilayers at RT and a pressure of about 1 bar causes an increase in the biquadratic coupling constant J2, while the values of J1 and J3 are reduced. A comparison of the obtained experimental results and available theoretical models leads to the conclusion that the mechanism of “fluctuating thickness of the non-magnetic spacer” could be responsible for the biquadratic exchange coupling. On the other hand, the “loose spins” model can explain the cubic coupling in the V/Fe multilayers. The modification of the interlayer exchange coupling using hydrogen is fully reversible.

Dynamic magnetic behaviors and magnetocaloric effect of CrI3-like bilayer structure

Abstract Through the utilization of Monte Carlo simulations, the dynamic magnetic characteristics and magnetocaloric effect of a CrI3-like bilayer structure featuring mixed spin (3/2, 1) are explored. First, a detailed analysis is conducted on the influence of different parameters such as exchange coupling and dynamic magnetic field on the order parameter, susceptibility, and internal energy of the ferrimagnetic system. Various interesting phenomena have been discovered, such as the occurrence of a maximum in the magnetization curve, a double-peak behavior in the magnetic susceptibility curve, and the blocking temperature exhibiting an initial increase followed by a subsequent decrease with the increase of the bias field. During the investigation of hysteresis loops, a multi-loop phenomenon is observed. Various parameters are being examined to evaluate how they affect the magnetic entropy change, adiabatic temperature, and relative cooling power of the ferromagnetic system. These discoveries could prove advantageous when implementing them in spintronic devices and refrigeration technology.

Synthesis of FeSiAl/SrFe12O19 soft magnetic composite materials with low magnetic loss

AbstractFeSiAl/SrFe12O19 soft magnetic composite material was prepared by mechanically crushing FeSiAl powder and M‐type permanent magnet hexagonal ferrite powder according to a certain quality. Their structures, morphologies, and magnetic properties were studied using x‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), SQUID, and B−H analyzers. Compared to organic and other inorganic composite materials, SrFe12O19 has a higher thermal decomposition temperature. The x‐ray diffraction pattern indicates that SrFe12O19 phase was detected in the sample. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) images show that powdered SrFe12O19 is dispersed on the surfaces and gaps of particles of different sizes. The magnetic analysis results indicate that although SrFe12O19 increases the hysteresis loss of the material, its good insulation reduces eddy current loss. When the content of SrFe12O19 is 2 wt.‐%, the magnetic loss is the lowest. The lower magnetic loss and higher thermal decomposition temperature of this composite material make it have a wider range of application prospects.

METHODOLOGY FOR EXPERIMENTAL RESEARCH ON THE DISTRIBUTION OF ENERGY IN THE ELEMENTS OF THE «VIBRATION MACHINE – COMPACTING CONCRETE MIXTURE» SYSTEM

The paper presents a methodology for experimental research on the distribution of energy in the elements of a vibra-tion machine for compacting concrete mixtures. The development of this methodology is based on a thorough analy-sis of existing research methods and the determination of energies in mechanical systems and media. Within the general system of the "vibration machine – compacting concrete mixture," the following subsystems were identified: bearings of the vibration exciter, supports, vibration dampers, reactive and active masses, including the form mass and the compacting concrete mixture. Specific research methods for energy dissipation were determined for each of the mentioned subsystems, preceding relevant modeling. Energy dissipation depends on many factors: the composi-tion and structure of the material, cyclic deformation and stresses arising from the medium’s exposure, the type and parameters of the load, the duration of cyclic deformation, and more. The evaluation criterion for energy dissipa-tion in media is the energy absorption coefficient, which expresses the ratio of energy used to perform the techno-logical process of compaction to the potential energy. The ratio of these energies is considered an independent material characteristic, determined experimentally, taking into account actual technological and operational fac-tors. It was found that the following main methods are used to evaluate energy parameters: phase, damping oscilla-tions, hysteresis loops, energy, and resonance methods. The paper substantiates the methodology for experimental research of parameters and energy indicators of concrete mixture compaction processes. Two models—discrete and continuous—were used in the simulation of these processes.

Mechanical properties and mechanism of damage and deterioration of coal under cyclic loading

To analyze the mechanical characteristics of damaged coal bodies and the mechanisms of evolution and degradation of internal pore and fracture defects under cyclic loads, raw coal containing original pore and fracture materials was selected as the research material. This study investigates the impact of cyclic loading on the mechanical properties of damaged coal and the evolution of flaw structures, such as pores and cracks, within the coal. A micro-fracture size judgment index (Ci) was defined based on fracture volume to determine the dominant macroscopic failure mode in coal bodies. The results indicate that a “hysteresis loop” forms in the loading and unloading curves of each cycle due to cyclic loading. During the cyclic loading and unloading phase, both the loading elastic modulus and the damage parameters of coal samples increase proportionally with the level of loading and the number of cycles. In the constant amplitude cyclic loading and unloading phase, there is minimal variation in the loading elastic modulus and damage parameters of coal samples, indicating their stability. As micro-scale fractures evolve within the coal body, pores with a volume less than 109 μm3 decrease with increasing cyclic loading and unloading during amplification cycles but remain relatively stable during equal amplitude cyclic loading phases. The contribution rate of damage to fractures with a volume between 109 and 1011 μm3 increases with higher load levels and cyclic loading/unloading during both amplification and equal amplitude cycles. The minimum order of magnitude for fracture volume that dominates macroscopic failure in the coal body is determined to be 109 and 1010 μm3.

Giant energy storage density with ultrahigh efficiency in multilayer ceramic capacitors via interlaminar strain engineering

Dielectric capacitors with high energy storage performance are highly desired for advanced power electronic devices and systems. Even though strenuous efforts have been dedicated to closing the gap of energy storage density between the dielectric capacitors and the electrochemical capacitors/batteries, a single-minded pursuit of high energy density without a near-zero energy loss for ultrahigh energy efficiency as the grantee is in vain. Herein, for the purpose of decoupling the inherent conflicts between high polarization and low electric hysteresis (loss), and achieving high energy storage density and efficiency simultaneously in multilayer ceramic capacitors (MLCCs), we propose an interlaminar strain engineering strategy to modulate the domain structure and manipulate the polarization behavior of the dielectric mediums. With a heterogeneous layered structure consisting of different antiferroelectric ceramics [(Pb0.9Ba0.04La0.04)(Zr0.65Sn0.3Ti0.05)O3/(Pb0.95Ba0.02La0.02)(Zr0.6Sn0.4)O3/(Pb0.92Ca0.06La0.02)(Zr0.6Sn0.4)0.995O3], our MLCC exhibits a giant recoverable energy density of 22.0 J cm−3 with an ultrahigh energy efficiency of 96.1%. Combined with the favorable temperature and frequency stabilities and the high antifatigue property, this work provides a strain engineering paradigm for designing MLCCs for high-power energy storage and conversion systems.

STUDY PHASE STRUCTURE, CATION DISTRIBUTION AND MAGNETIC PROPERTIES OF COBALT, MAGNESIUM AND COPPER FERRITES

An analysis to the characteristics of Co, Mg and Cu ferrites that were prepared using sol–gel method and annealed at [Formula: see text]C for 1 hour, performed using X-ray diffraction and Raman spectroscopy for structural characteristics, while the Vibrating Sample Magnetometer (VSM), was used for the magnetic characteristics. The X-ray analysis of both cobalt and magnesium ferrites shows a reverse crystal structure of a cubic spinel, while copper ferrite shows a tetragonal crystal structure characteristic at this annealing temperature. The lattice constant (a) was found to be [Formula: see text] for CoFe2O4, [Formula: see text] for MgFe2O4 and [Formula: see text] for CuFe2O4. The Raman spectrum confirms a spinel crystalline form of the prepared ferrites where a likely distribution of cation is indicated at the tetrahedral and octahedral sites. The peaks of the Raman shift appear between 200–800[Formula: see text]cm[Formula: see text]. These peaks indicate the formation of ferrites. The hysteresis loop of CoFe2O4 indicates a hard magnet material. Cu ferrites have relatively lower remnants and magnetocrystalline anisotropy, which indicates soft magnetic characteristics even though it showed higher coercivity. The squareness ratio (Mr/Ms) values varied between 0.52, 0.13 and 0.57 for CoFe2O4, MgFe2O4 and CuFe2O4, respectively. These insights highlight the possibility of tuning the properties of ferrites using a cost-effective sol–gel method.

Hysteresis loop shape of field-driven antiferromagnetic-ferromagnetic bilayers in experimental conditions

Hysteresis loop shape of field-driven antiferromagnetic-ferromagnetic bilayers in experimental conditions

Discretizing the bistability of mode-locked electron spin precession: An Overhauser field hysteresis manifestation

Electron-nuclear spin interactions by pulsed optical pumping have been found to polarize the nuclear spin system, leading to the nuclei building up an intrinsic magnetic field known as the Overhauser field. Studies have indicated an Overhauser field hysteresis effect dependent on the sweep direction of an externally applied magnetic field in negatively detuned periodically pumped Si-doped GaAs. Although predictions of bistable mode-locked electron spin precession frequency modes have been made for systems exhibiting this hysteresis, there have been no reports on the experimental observation of said bistable spin precession modes. This report details the evolution of bistable Overhauser field solutions leading to a hysteretic effect in negatively detuned optical excitation of Si-doped GaAs by magneto-optic pump–probe spectroscopy in the Voigt geometry and investigates the resulting consequence of this hysteresis acting on the electron spin system. One manifestation of the Overhauser field hysteresis acting on the electron spin system leads to the discretization of bistable mode-locked electron spin precession modes within a given band of externally applied magnetic fields. A method for preferentially accessing the two different and stable mode-locked spin precession modes within a given band of externally applied magnetic field is outlined, which may be of interest for communities utilizing electron and nuclear spins for information processing protocols.

Application of chokeberry biochar as a modified additive to the vegetable lubricants: the tribological and rheological properties

Effect of modifying a vegetable grease with different amounts of chokeberry biocarbon on its tribological and rheological properties. The aim of the research was to investigate the effect of the incorporation of biochar derived from the pyrolysis of chokeberry biomass at 500 and 700 °C respectively, in lubricants formulated with vegetable oil, on their functional characteristics in terms of tribology and rheology. Fumed silicon dioxide was utilized as a thickening agent, ensuring the production of lubricants with a consistency class of II. The biochar was introduced into the lubricating formulations in concentrations of 1, 3, and 5%. A rapeseed-based grease with commercial activated carbon served as the reference sample. The research focused on assessing how this innovative additive influenced both the tribological and rheological behaviors of the resulting lubricants. The study evaluated the effects of chokeberry-derived biochar on the wear resistance and scuffing prevention properties of the vegetable-based greases. Additionally, the biochar’s influence on various rheological parameters such as flow curves, viscosity profiles, hysteresis loops, and viscoelastic characteristics was analyzed. Results demonstrated that the biochar additive considerably enhanced the tribological and rheological performance of the tested rapeseed-based grease.

How large are hysteresis effects? Estimates from a Keynesian growth model

How large are hysteresis effects? Estimates from a Keynesian growth model

An unsteady aerodynamic force calculation method for shear variable-sweep wing considering sweep angle and airfoil changes

The backward shift of the aerodynamic center and insufficient morphing capability are critical design bottlenecks of traditional rotary variable-sweep wings. This paper presents a new shear variable-sweep morphing form that reduces the backward shift of the aerodynamic center by allowing the leading edge of the wing to slide forward. The shear variable-sweep wing (SVSW) with this morphing form enables coordinated changes in both planform and airfoil shape, achieving greater aerodynamic benefits. However, during the shear morphing process, the wing experiences unsteady aerodynamic phenomena, and this multi-dimensional morphing form further complicates the calculation of unsteady aerodynamic forces. To address this challenge, this paper investigates the three-dimensional changes of the SVSW surface during the shear morphing process and proposes an unsteady aerodynamic force calculation method, which considers variations in sweep angle and airfoil. The results showed that as the sweep angle increases, both the lift and drag coefficients decrease, and the unsteady aerodynamic characteristics exhibit significant flow hysteresis, with the unsteady lift and drag coefficients deviating from the steady-state results and forming a clockwise dynamic hysteresis loop. Finally, the study analyzed the effects of shear morphing rates and flow conditions on the wing's unsteady aerodynamic characteristics and validated the feasibility and effectiveness of the proposed method through continuous morphing wind tunnel tests. The proposed method also fully considers the effects of shear motion, curved aerodynamic configurations, and unsteady vortices on aerodynamic characteristics, offering a low-cost and effective solution for the optimization design and aeroelastic analysis of the SVSW.

Microstructural study with enhanced dielectric and magnetic properties of M−type Nd doped Ba1-xNdxFe12O19 (x = 0–0.20) hexaferrites synthesized via sol–gel auto-combustion route

In the present study, we have examined the influence of Nd doping on the structural, morphological, magnetic, and dielectric properties of barium hexaferrite (Ba1-xNdxFe12O19; 0 ≤ x ≤ 0.20) samples synthesized via the sol–gel auto-combustion route. The XRD patterns confirm the formation of the hexagonal phase, in addition to minor traces of Fe2O3 impurity in the samples. Doping with Nd3+ ions produced strain in the crystal, and the samples retain their hexagonal phase with space group P63/mmc, as ensured by the Rietveld refinement method. FTIR spectroscopy were performed for microstructural analysis, which shows the corresponding stretching and bending bands of iron and oxygen in the samples. The Raman spectra confirmed the Raman fundamental modes at various wavenumbers, which also confirm the hexagonal structure of the samples. The electronic states of all metal ions state were confirmed through x-ray photoelectron (XPS) spectroscopy analysis, which show that iron is present in two oxidation states (Fe2+ and Fe3+) in all the prepared samples. XPS spectra also revealed that the Nd-doped sample is more defective as compared to pure sample. Scanning electron microscopy (SEM) micrographs shows that the non-uniform particle size in the nanometer range. Elemental composition is confirmed using energy dispersive x-ray spectroscopy (EDS) measurement. Additionally, magnetic measurements using a vibrating sample magnetometer (VSM) revealed that the hysteresis loops for 5 % Nd-doped sample shows the maximum value 44.3 emu/g of magnetization, and its values decrease for further increase in Nd doping concentration. The dielectric measurements were performed at room temperature in the frequency range of 1 Hz to 10 MHz, when Nd3+ is doped at the Ba site, it enhances the dielectric constant, dielectric loss, tangent loss, and ac conductivity of the synthesized samples.

Assessment of dwell-fatigue properties of nickel-based superalloy coated with a multi-layered thermal and environmental barrier coating

A three-layered experimental thermal and environmental barrier coating (TEBC) was deposited using air plasma spraying technology on cylindrical specimens of nickel-based superalloy MAR-M247. TEBC consists of mullite (Al6Si2O13) and hexacelsian (BaAl2Si2O8) upper layer, Y2O3 stabilised ZrO2 interlayer and CoNiCrAlY bond coat deposited on the grit-blasted surface of MAR-M247. The cyclic plastic response and damage mechanisms in uncoated and TEBC-coated MAR-M247 have been studied in isothermal dwell-fatigue tests conducted under strain control with constant strain amplitude at 900 °C. In each cycle, 5-minute dwells were introduced in both tensile and compression peaks of the hysteresis loop. Fatigue hardening/softening curves, stress relaxation curves, cyclic stress-strain curves and fatigue life curves are reported. Ceaseless mild softening has been found in both uncoated and TEBC-coated MAR-M247. TEBC-coated MAR-M247 showed an improved lifetime in the whole range of tested strain amplitudes. Data obtained from stress relaxation curves were used to assess the fraction of creep damage. The generalised damage accumulation rule was used to evaluate damage due to fatigue-creep-environment interaction. A study of the surface relief and internal microstructure using SEM and TEM helped to interpret the specifics of fatigue behaviour of uncoated and TEBC-coated material. The effectiveness of this newly developed TEBC, together with the dwell sensitivity of MAR-M247, were discussed from the perspective relevant to dwell-fatigue cyclic straining.

Testing and simulation of the hysteresis characteristics of magnetostrictive materials under harmonic excitation

As various power electronic devices are widely used in the power grid, the current flowing through the drive winding of the magnetostrictive actuator inevitably contains harmonic components. The flux density within the hysteresis material is non-sinusoidal with harmonic components, which distorts the hysteresis characteristics of the material and affects the accurate calculation of losses. This paper builds a harmonic magnetic performance testing platform for magnetostrictive materials to test and analyze the magnetic properties under different excitation conditions (magnetic density amplitude, harmonic order, and harmonic content). To complete the mathematical description of the static hysteresis model containing closed minor hysteresis loops, two pinning coefficients k1(Bn,kTHD) and k2(Bn,kTHD), which are related to the degree of harmonic distortion, are used to express the rate of change of the irreversible magnetization components. Fractional order derivative and harmonic frequency-dependent terms are used to characterize the eddy losses and excess losses mathematically. Finally, the dynamic hysteresis model under harmonic excitation is developed. Comparative analysis of model calculation results and experimental test data shows that the model can not only accurately simulate the distorted hysteresis characteristics but also predict the loss of magnetostrictive materials. This research is of significance to the optimal design and temperature rise analysis of magnetostrictive devices.

Structural characteristics of a supersonic turbulent boundary layer subject to convex–concave curvature coupling

With an inflow Mach number of 3.0, the structural characteristics of a supersonic turbulent boundary layer subject to a convex–concave coupled curvature are experimentally investigated by Nano-tracer Planar Laser Scattering (NPLS) technology. The NPLS images reveal intricate flow features, including multi-scale vortices, near-wall streaks, and oblique shock waves. Wall pressure measurements indicate a feedback mechanism between the turbulent structures and wall pressure within the curvature coupling region, resulting in the upstream shift of the minimum pressure point into the convex wall. Additionally, the oblique shock generated by the concave curvature leads to an increased wall pressure in the downstream flat plate. By utilizing fractal dimension analysis and two-point spatial correlation analysis, the complexity and morphology of the turbulent vortices are quantitatively described. It is found that no significant changes in fractal dimension near the curvature coupling point due to the hysteresis effect. Furthermore, the coherent structures in the inner boundary layer shrink before and after the curvature coupling point, also attributed to hysteresis. The turbulence structures in the middle layer show lower sensitivity to the convex curvature, indicating distinct responses of turbulence structures at different normal positions to the wall's geometric features. Statistical analysis of the vortex structures, including maximum Feret diameter, aspect ratio, and inclination angles, further confirms the enhanced vortex breaking up caused by the concave wall and the increased size disparities of vortex structures due to curvature variations.

Time-Varying Risk Aversion and Inflation-Consumption Correlation in an Equilibrium Term Structure Model

Abstract Inflation risk premiums tend to be positive in an economy mainly hit by supply shocks, and negative if demand shocks dominate. Risk premiums also fluctuate with risk aversion. We shed light on this nexus in a linear-quadratic equilibrium macro-finance model featuring time variation in inflation-consumption correlation and risk aversion. We obtain analytical solutions for real and nominal yield curves and for risk premiums. While changes in the inflation-consumption correlation drive nominal yields, changes in risk aversion drive real yields and act as amplifier on nominal yields. Combining a trend-cycle specification of real consumption with hysteresis effects generates an upward-sloping real yield curve. Estimating the model on U.S. data from 1961 to 2019 confirms substantial time variation in inflation risk premiums: distinctly positive in the earlier part of our sample, especially during the 1980s, and turning negative with the onset of the new millennium.