Hysteresis Shape Research Articles

ECAP based regulation mechanism of shape memory properties of NiTiNb alloys

NiTiNb is a kind of wide hysteresis shape memory alloy with great application potential in aerospace. However, the mechanism of improving the shape memory properties of the NiTiNb alloy by tailoring grain size and grain boundary type has not been well identified. Accordingly, taking equal channel angular pressing (ECAP) as the grain refinement method, this paper focused on the regulation mechanism of grain size and grain boundary type on the shape memory properties. First, grain refinement structures with a special distribution of low- and high- angle grain boundaries (LAGBs and HAGBs) were prepared by ECAP with different passes. Then, the mechanism of the grain boundary on the shape memory properties was first revealed. It was found that many LAGBs appeared in NiTiNb alloy after ECAP, and with increasing of ECAP passes, the LAGBs were transformed into the HAGBs, achieving grain refinement. The stress-induced transformation produced (001) compound twins in the dense sub-microcrystalline region surrounded by LAGBs, leading to a non-monotonic variation of transformation strain with decreasing grain size. Meanwhile, with the decrease of grain size (or the increase of grain boundary content), the transformation hysteresis temperature and recovery stress of the NiTiNb alloy increased simultaneously. To obtain better shape memory characteristics, we can tailor the type and distribution of specific grain boundaries through the design of ECAP.

High-frequency magnetic response of superferromagnetic nanocomposites

Studies of the dynamical response of thin-film composites of magnetic nanoparticles embedded in dielectric matrices to the oscillatory magnetic field of the microwave-frequency range are performed using numerical simulations. Four soft-magnetic systems; (Co)0.42(MgF2)0.58, (Fe65Co35)0.57(SiO2)0.43, (Fe65Co35)0.75(Al2O3)0.25, (Fe65Co35)0.6(Al2O3)0.4, typical of a class of ”high-frequency ferromagnetic nanocomposites” are simulated. The necessary micromagnetic parameters are extracted from data within the model of random magnetic anisotropy (RMA). Those materials are candidates for use in micro-converters of power (inductors and transformers) due to their high saturation magnetization, high resistivity, and absence of intra-grain magnetic domains. Thus, they are able to create a high magnetic flux at low power losses. The simulations allow for an inspection into details of the spatial distribution of the oscillating magnetization. We predict noticeable differences in the ferromagnetic resonance (FMR) in different composites which are related to the shape of the static hysteresis. Operating ranges of the driving-field amplitude are related to the hysteresis width. Next to FMR, we analyze the magnetic response via the oscillatory motion of domain walls in a longitudinal field. Besides the response to the alternating field of a constant direction, we study the magnetization dynamics driven by in-the-plane-rotating field. Such a field can drive the magnetization rotations which are a strong-response (nonlinear) mode potentially useful for efficient power conversion.

Degree of Anthropogenic Land Disturbance Controls Fluvial Sediment Hysteresis.

Storm events dominate sediment delivery to stream corridors, but the effects of anthropogenic disturbances on altering the sources, pathways, and timing of delivery remain uncertain. To address this knowledge gap, we analyzed 849 events from over a decade of high-frequency turbidity data across five watersheds in an urbanization gradient. Sensing results suggested that hysteresis patterns evolved with land use from clockwise (low-rural) to figure-eight (high-rural) to counter-clockwise (high-urban), indicating a disturbance-driven shift of sediment provenance from proximal to distal. Sediment loading pathways in the lowest-disturbance rural watershed were dominated by a single hysteresis shape (>90% of export by clockwise events), whereas the most-disturbed urban basin had the greatest variability in loading pathways (∼25% of export by clockwise, counter-clockwise, figure-eight, and complex events, respectively). Finally, wastewater treatment facilities modulated the release of "hungry-water" baseflow, causing more-rapid periods of high streamflow variance in catchments with a treatment facility (∼4 h period) than in those without (∼6 h period). Together, our results indicate that anthropogenic disturbances, including tile drainage, impervious surfaces, and roadway density, increase the connectivity of distally located sediment that would-in undisturbed basins-deposit along the sediment cascade. This information is important to watershed managers as they mitigate erosion in developing basins.

First detection of low field microwave absorption in the disordered multiferroic double perovskite BiFe0.5Mn0.5O3

BiFe0.5Mn0.5O3 (BFMO) is an intriguing magnetic double perovskite, only obtainable through high pressure-high temperature synthesis. It shows bulk multiferroic properties, namely the coexistence between a spin canted antiferromagnetic structure superimposed to an externally induced electric polarization at least from 77 K. In particular, the system is characterized by a significant weak ferromagnetic hysteresis loop and by a very rare phenomenon: the spontaneous magnetization reversal (MRV) versus temperature in the low field regime. To clarify the BFMO exotic magnetic phase in the low field regime, the Electron Spin Resonance (ESR) and the low field microwave absorption (LFMA) techniques were used, providing the first observation of LFMA in the bulk BFMO as an additional functionality of this material. A striking feature is that the hysteresis in LFMA signals vanishes above 45 K, while the bulk M-H loop hysteresis, measured in the same field range of LFMA, persists till room temperature. The temperature at which LFMA hysteresis vanishes qualitatively matches the position of the magnetic susceptibility’s second derivative peak, corresponding to the temperature at which the local second order mechanism responsible for MRV is maximum. The line shape of LFMA completely changes above 45 K and the ESR linewidth starts decreasing above this temperature, indicating the role of defect/disorder induced inhomogeneity. The temperature evolution of LFMA hysteresis and line shapes as a measure of the competition between Fe- and Mn-rich clusters suggests a sort of local frustration at the microscopic scale, responsible for the peculiar magnetization reversal of this system.

Stable and unstable trajectories in a dipolar chain

In classical mechanics, solutions can be classified according to their stability. Each of them is part of the possible trajectories of the system. However, the signatures of unstable solutions are hard to observe in an experiment, and most of the times if the experimental realization is adiabatic, they are considered just a nuisance. Here we use a small number of XY magnetic dipoles subject to an external magnetic field for studying the origin of their collective magnetic response. Using bifurcation theory we have found all the possible solutions being stable or unstable, and explored how those solutions are naturally connected by points where the symmetries of the system are lost or restored. Unstable solutions that reveal the symmetries of the system are found to be the culprit that shape hysteresis loops in this system. The complexity of the solutions for the nonlinear dynamics is analyzed using the concept of boundary basin entropy, finding that the damping timescale is critical for the emergence of fractal structures in the basins of attraction. Furthermore, we numerically found domain wall solutions that are the smallest possible realizations of transverse walls and vortex walls in magnetism. We experimentally confirmed their existence and stability showing that our system is a suitable platform to study domain wall dynamics at the macroscale.

Hysteresis in centrosymmetric CuPbI3 perovskite halide: apolar dielectric or orientable dielectric?

We demonstrated the change in polarization behaviour at the surface/interface before and after light through Havriliak–Negami equation of lesser known CuPbI3. We have synthesized CuPbI3 through cold sintering technique and the polarization mechanisms are altered by increasing (cold) sintering temperature. The structure of CuPbI3 was not known and we predicted it to be hexagonal (Rm) with 21R prototype representation. The hysteresis is reported to be affected by ferroelectricity (reorientable dipoles with non-centrosymmetry), to inspect this a centrosymmetric CuPbI3 is taken. In spite of centrosymmetry, we observed that the hysteresis area and shape of IV curve in AM 1.5 G sunlight shows the drastic variation with the change in polarization behaviour. Our experimental results suggest that apolar dielectric behaviour is the cause of I–V hysteresis rather than robust ferroelectric polarization (which was absent in the present case).

Structural and Magnetic Tuning of LaFeO3 Orthoferrite Substituted Different Rare Earth Elements to Optimize Their Technological Applications

Lanthanum partially substituted rare earth (RE) elements to form RE0.7La0.3FeO3; RE = Ce, Pr, Nd, Sm and Gd) nanoparticles. They were synthesized using the citrate–nitrate auto-combustion method. The crystal structure and microstructure were refined by applying Rietveld profile refinements using the Maud Program. The morphology, magnetic and optical properties of the inspected samples have been explored using HRTEM, VSM, and UV–Vis diffuse reflectance, respectively. The prepared-samples distortion increases as the substituted RE ionic radius decreases. Iron spins of RE orthoferrite samples are known to be ordered Anti-ferromagnetically (AFM). They also possess weak ferromagnetism due to the Dzyaloshinskii-Moriya interaction. This feeble ferromagnetism is reflected in their soft behavior, whereas Sm0.7La0.3FeO3 sample exhibits the butterfly shape hysteresis loop. The remnant magnetization, saturation magnetization, and coercivity are relatively small, but sometimes impressively, enhanced through Lanthanum-rare-earth substitution. Introducing rare earth ions into LaFeO3 decreases the Fe–O–Fe angle and the consequent reduction of the super exchange interaction. In particular, the coercivity of Sm0.7La0.3FeO3 is remarkably improved relative to the parent sample. It has the largest coercivity of all the prepared nanoparticles. Due to the aforementioned substitution, a slight reflectance edge red shift is observed in the spectra. The relation between the magnetic properties of the investigated samples and the ionic radii of RE was investigated and discussed. The experimental results of this work can provide fundamental support for the research and development of multiferroic materials.

Impact of the Nonlinear Dielectric Hysteresis Properties of a Charge Trap Layer in a Novel Hybrid High-Speed and Low-Power Ferroelectric or Antiferroelectric HSO/HZO Boosted Charge Trap Memory

A novel hybrid antiferroelectric (AFE)-based charge trap (CT) memory is reported focusing on an amplified tunnel oxide field ( ${E} _{\text {TO}}$ ) via the dynamic of an AFE hysteresis dipole switching. The role of dynamic permittivity increase and the saturated polarization at the instant of the write operation are explored for enhanced ${E} _{\text {TO}}$ . The hybrid CT concept is studied by benchmarking the controlled properties of the HfO2 CT layer via the Si elemental doping in order to stabilize the linear dielectric (DE), ferroelectric (FE), or AFE response. The Si-doped HfO2 (HSO) with AFE stabilized phase shows the largest memory window (4.5 V) compared to the DE- or FE-based CT layers. The dynamic AFE dipole switching enables a maximized ${E} _{\text {TO}}$ at the instant of switching such that a high-speed and low-power CT memory is realized. The role of the tailored hysteresis shape on the ${E} _{\text {TO}}$ magnitude is studied for different Si contents and benchmarked to the Zr-doped hafnium oxide (HZO). The AFE CT multilevel coding as 1–3 bit/cell, the role of the pass voltage disturb, and a mini-NAND array operation are demonstrated. The global variability and area scalability of the HSO CT devices are studied to indicate the effect of Si content distribution and the area dependence of the AFE film variability. AFE CT devices are characterized for a switching speed ( $ ), ten-year data retention, and $10^{{5}}$ endurance. Moreover, the improved CT characteristics by the AFE dipole switching are explored for enhanced long-term potentiation and depression of a synaptic device.

CFD modelling of the effect of capillary pressure on retention behaviour of water menisci at inter-particle contacts

This paper presents a Computational Fluid Dynamics (CFD) model on the effect of capillary pressure on the retention behaviour of a granular material. The model proposes an unprecedented CFD insight into the onset of liquid menisci at the inter-particles contact under varying hydraulic conditions. The present work models the material grains as smooth spherical particles that define a porous network filled by two interstitial fluids: air and silicon oil. The numerical model has been subsequently validated against experimental measurements of the degree of saturation at different capillary pressures taken by Dullien et al. [F.A. Dullien, C. Zarcone, I.F. MacDonald, A. Collins, R.D. Bochard. J. Colloid Interface Sci. 127, 2 (1989)] in a system of smooth glass beads flooded with silicon oil. Results from the numerical simulations confirm the good capability of the model to reproduce the experimental retention behaviour of the granular material. Finally, the present paper laid the basis for future CFD studies on the effect of various factors (e.g. hydraulic hysteresis, surface roughness and/or grain shape) on the capillary pressure acting at the interparticle contact.

Storm event impacts on in-stream nitrate concentration and discharge dynamics: A comparison of high resolution in-situ measured data with model simulations

The relationship between nitrogen and discharge (N-Q) in a stream can be captured with high frequency nitrate nitrogen (NO3−-N) samplers. In Austria, the Raab catchment (998 km2) has high frequency NO3−-N data measured with a spectrometer probe. This study evaluated if the widely-used and typically calibrated eco-hydrological model Soil and Water Assessment Tool (SWAT) can reproduce the hysteresis loop direction and the dilution or accretion effects of NO3−-N dynamics during storm events in this agricultural catchment. The daily aggregated NO3−-N measurements were compared with the daily SWAT simulated discharge and NO3−-N concentrations of 14 storm events by computing hysteresis indices - loop direction and area (h index), loop direction (HInew) and solute gradient (∆C). Overall, the SWAT model was able to replicate the predominant anticlockwise hysteresis and dilution effect of NO3−-N in the Raab catchment. The loop direction was simulated correctly in 9 and 10 events, for the h and HInew indices, respectively. The hysteresis direction inferred from both indices did not always concur due to the differences in the calculation methods. The dilution or accretion effect was simulated correctly in 9 of the events. However, the SWAT model only correctly simulated the N-Q relationships for all three hysteresis criteria in 5 of the 14 events. Due to the aggregation of measured data to the daily time step, information pertaining to the hysteresis shape was sometimes lost, particularly if the storm event was <4 days in duration. Structural limitations of the SWAT as well as specific relevant basin parameters (parameters that have one value for the entire catchment) may restrict simulating N-Q dynamics. An enhanced calibrated and validated model would possibly improve the results, since the events during the better calibrated period more often reproduced the measured hysteresis indices.

The Magnetoelectric Effect in Ferroelectric/Ferromagnetic Film Hybrid Systems with Easy-Plane and Easy-Axis Anisotropy

The striction magnetoelectric effect in hybrid systems consisting of a magnetic film applied on the surface of a ferroelectric has been investigated. Films with planar (galfenol, nickel) and perpendicular (Co/Pt multilayer structures) magnetic anisotropy have been used. A PMN–PT crystal has served as ferroelectric. The hysteresis loops of magnetic films have been studied as a function of voltage applied to the ferroelectric crystal. A voltage applied to films with easy-plane anisotropy causes the anisotropy axis to turn in the plane of the sample. In structures with easy-axis anisotropy, the hysteresis shape changes, which, according to numerical simulation, may be associated with a change in interfacial Dzyaloshinsky–Moriya interaction at the Co/Pt interface.

Transient and Harmonic Unipolar Hysteresis Model of Piezoelectric Actuators Using a System-Level Approach

Thanks to their integrability and good electromechanical conversion abilities, piezoelectric actuators are a good choice for many actuation applications. However, these elements feature a frequency-dependent hysteresis response that may yield complex control implementation. The purpose of this paper is to provide the extension of a simple hysteresis model based on a system-level approach linking the strain derivative to the driving voltage derivative and taking into account the dynamic behavior of the hysteretic response of the actuator. The proposed enhancement consists of transient and harmonic regimes, allowing to extend the quasi-static model to dynamic behavior with any frequency. In particular, initial strain shift arising from stabilization and accommodation effects as well as frequency-dependent hysteresis shape are considered. The inclusion of the system dynamics in the model is obtained thanks to fractional derivatives and associated fractional transfer functions, allowing the consideration of the full actuator history as well as a fine tuning of the system dynamics over a wide frequency band. Finally, a numerical example of linearized control through compensation loop is provided, demonstrating the interest in the proposed approach for providing a computationally-efficient, simple yet efficient way for finely predicting the actuator response and thus designing appropriate controllers.

Ballooning, bulging, and necking: An exact solution for longitudinal phase separation in elastic systems near a critical point

Prominent examples of longitudinal phase separation in elastic systems include elastic necking, the propagation of a bulge in a cylindrical party balloon, and the beading of a gel fiber subject to surface tension. Here we demonstrate that if the parameters of such a system are tuned near a critical point (where the difference between the two phases vanishes), then the behavior of all systems is given by the minimization of a simple and universal elastic energy familiar from Ginzburg-Landau theory in an external field. We minimize this energy analytically, which yields not only the well known interfacial tanh solution, but also the complete set of stable and unstable solutions in both finite and infinite length systems, unveiling the elastic system's full shape evolution and hysteresis. Correspondingly, we also find analytic results for the the delay of onset, changes in criticality, and ultimate suppression of instability with diminishing system length, demonstrating that our simple near-critical theory captures much of the complexity and choreography of far-from-critical systems. Finally, we find critical points for the three prominent examples of phase separation given above, and demonstrate how each system then follows the universal set of solutions.

Hysteresis analysis to quantify and qualify the sediment dynamics: state of the art.

This work is a review of the use of hysteresis to quantify sediment discharge dynamics. We reviewed 71 journal articles from the year 1953 to the present day focusing on two topics: the factors that influence hysteresis; and hysteresis quantification. The main factors influencing hysteresis are: (a) magnitude and sequence of events; (b) sediment particle size distribution; (c) basin size; and (d) land use and sediment source. Hysteresis quantification can be done using several different methods that can be grouped as: (a) hysteresis indexes; (b) statistical analysis; and (c) uncertainty analysis. Most studies were conducted in Western Europe and the USA. The studies, in general, show how the factors listed above influence the shape and patterns of hysteresis. However, the sediment dynamics are complex, and the hysteresis patterns may be linked to many other factors, such as slope and drainage systems. The quantification of hysteresis still appears, mainly with the hysteresis index and statistical analysis. Therefore, there are still many other factors that influence hysteresis patterns, as well as hysteresis rates and uncertainty analyses.

Unusual Field Dependence of the Anomalous Hall Effect in Ta/Tb−Fe−Co

Experimental studies of anomalous Hall effect are performed for thin filmed Ta/TbFeCo in a wide range of temperatures and magnetic fields up to 3 T. While far from the compensation temperature (TM=277 K) the field dependence has a conventional shape of a single hysteresis loop, just below the compensation point the dependence is anomalous having the shape of a triple hysteresis. To understand this behavior, we experimentally reveal the magnetic phase diagram and theoretically analyze it in terms of spin-reorientation phase transitions. We show that one should expect anomalous hysteresis loops below the compensation point if in the vicinity of it the magnetic anisotropy is dominated by FeCo sublattice due to interaction with Ta.

Diode Heterostructures with a Ferromagnetic (Ga,Mn)As Layer

Diode p-(GaMn)As/n-InGaAs/n+-GaAs heterostructures with different thicknesses (from 5 to 50 nm) of the (Ga,Mn)As dilute magnetic semiconductor layer have been fabricated and studied. The negative magnetoresistance effect reaching 6–8% is observed in a magnetic field of 3600 Oe; this effect is retained up to temperatures of 70–80 K and related to a decrease in the charge carrier scattering due to ferromagnetic ordering in the (Ga,Mn)As layer. The dependence of the magnetoresistance on the forward bias voltage is nonmonotonic, and the magnetoresistance maximum and the operating voltage rate are dependent on the (Ga,Mn)As layer thickness. The magnetic-field dependence of the magnetoresistance have a hysteresis shape determined by the influence of the tensile stresses in the (Ga,Mn)As layer grown above the relaxed InGaAs on the magnetization component perpendicular to the structure surface.

Snapping elastic disks as microswimmers: swimming at low Reynolds numbers by shape hysteresis

We illustrate a concept for shape-changing microswimmers, which exploits the hysteresis of a shape transition of an elastic object, by an elastic disk undergoing cyclic localized swelling. Driving the control parameter of a hysteretic shape transition in a completely time-reversible manner gives rise to a non-time-reversible shape sequence and a net swimming motion if the elastic object is immersed into a viscous fluid. We prove this concept with a microswimmer which is a flat circular elastic disk that undergoes a transition into a dome-like shape by localized swelling of an inner disk. The control parameter of this shape transition is a scalar swelling factor of the disk material. With a fixed outer frame with an additional attractive interaction in the central region, the shape transition between flat and dome-like shape becomes hysteretic and resembles a hysteretic opening and closing of a scallop. Employing Stokesian dynamics simulations of a discretized version of the disk we show that the swimmer is effectively moving into the direction of the opening of the dome in a viscous fluid if the swelling parameter is changed in a time-reversible manner. The swimming mechanism can be qualitatively reproduced by a simple 9-bead model.

Hysteresis Dispersion Compensation with Neural Network based Controller

Hysteresis is a commonly encountered physical phenomenon in many systems. It results in a dependence of the state of a system to its history. This non-linearity makes it particularly difficult to control accurately. There are many ways for compensating hysteresis, one of them consists of building an inverse model of the hysteresis and using it as a feedforward controller. Coupled to a feedback mechanism, the hysteresis impact can thus be minimized. However, the performance of these controllers decreases when exposed to dispersion in the hysteresis quantity or shape. The capacity of neural networks to model non-linear phenomena is not to be proven and will be put at use. In this paper, an artificial neural network model was trained to replace the conventional hysteresis inverse model. The controller performance was evaluated on a limited-angle torque motor, which exhibits hysteresis due to the magnetization saturation of the ferromagnetic materials. The experimental results pointed out the superior robustness to system dispersion of the Neural Network based controller for time and frequency response.

On stability of linear dynamic systems with hysteresis feedback

The stability of linear dynamic systems with hysteresis in feedback is considered. While the absolute stability for memoryless nonlinearities (known as Lure’s problem) can be proved by the well-known circle criterion, the multivalued rate-independent hysteresis poses significant challenges for feedback systems, especially for proof of convergence to an equilibrium state correspondingly set. The dissipative behavior of clockwise input-output hysteresis is considered with two boundary cases of energy losses at reversal cycles. For upper boundary cases of maximal (parallelogram shape) hysteresis loop, an equivalent transformation of the closed-loop system is provided. This allows for the application of the circle criterion of absolute stability. Invariant sets as a consequence of hysteresis are discussed. Several numerical examples are demonstrated, including a feedback-controlled double-mass harmonic oscillator with hysteresis and one stable and one unstable poles configuration.

Downstream hysteresis-shape control of a bistable optical signal created by an upstream nonlinear photonic resonator.

We experimentally demonstrate the control of the hysteresis shape of a bistable optical signal at a location downstream of the nonlinear photonic resonator within which the bistability is generated; this shape control mechanism is performed without any signal sent upstream to the bistable system. The downstream shape-control element consists of a fiber-optic polarization controller and linear polarizer in series, and the nonlinear resonator generates an optical signal whose bistable branches exhibit different states of power and polarization. The diversity of demonstrated hysteresis shapes include the canonical counter-clockwise (CCW) shape (S-shape), the clockwise (CW) shape (inverted S-shape), and butterfly shapes; since all shapes originate from the same bistable signal, all shapes exhibit the same switching input powers. Moreover, the shape-selection process enhances the bistable switching contrast to 20 and 21 dB for the CCW and CW shapes, respectively. The shape-selection technique is demonstrated using a Fabry-Pérot semiconductor optical amplifier, is applicable to other nonlinear photonic resonators, and provides flexibility to future combinational and sequential all-optical signal processing applications.