Magnetic Hysteresis Behavior Research Articles

Reconstructing Magnetic Hysteresis Behavior with Flux Model and Identifying Parameters for Dual-Coil MR Actuator

Magnetorheological (MR) actuators represent an important class of semi-active devices that have received extensive investigation and deployment in the field of vibration reduction systems. Their notable features include a significant reduction in energy consumption, along with an impressive tunable range of continuously controllable damping forces. The force output of these devices is a complex function that involves two hysteretic mechanisms: magnetic and mechanical (i.e. hydraulic). While the total hysteresis mechanism of these devices has been the subject of considerable study, comparatively little attention has been paid to their magnetic hysteretic behavior. In this study, the authors examine the behavior of the dual coil MR actuator’s control circuit and attempt to extract the magnetic flux information from the laboratory measurements of electrical signals applied to it. The study is further enhanced by the incorporation of the Bouc-Wen (B-W) hysteretic unit, which serves to replicate the flux-current (or magnetic) hysteretic relationship. The B-W model's parameters are identified through the use of a hybrid algorithm, namely the particle swarm optimization and fmincon hybrid optimizing strategy. It incorporates the advantages of both algorithms, resulting in an average improvement of 0.38% in standard deviation compared to fmincon, across 1A to 5A, when comparing the experimental and simulation data. This strategy is employed to fit the model predictions to the flux data, derived from the reconstructed flux and current in time histories. The findings of the study demonstrate that the B-W model is an effective tool for predicting the variation in magnetic flux in response to an exciting current. The results can be implemented for prototyping or validating a model-based controller for MR actuator systems.

Dynamic magnetic characteristics and hysteresis behaviors of a diluted graphene-like monolayer

Dynamic magnetic characteristics and hysteresis behaviors of a diluted graphene-like monolayer

Investigation of BSCCO Superconductors with Ga Substitution by Solid State Method

Samples of (Bi2-xGax)Sr2CaCu2O2 superconductors with varying Ga substitution levels (x=0, 0.06, 0.12, 0.20) were synthesized using the solid-state reaction method. The effects of partial substitution of bismuth and gallium elements on the BSCCO structure were investigated in terms of their electrical, magnetic, structural, and mechanical properties. X-ray diffraction (XRD) was used to determine the crystalline phases, and samples A and B exhibited sharp peaks, indicating well-crystallized material with no Ga2O3 phase. SEM images were used to obtain microscopic views of all samples, and the elemental compositions of each element were determined from EDX spectra. The critical temperature was calculated from R-t measurements, and Sample A exhibited the highest Tc at 96K. Magnetic properties were investigated for all samples, including magnetic hysteresis behavior and magnetic moment. The critical current density (Jc) values were calculated using the Bean model by utilizing magnetic hysteresis.

Monte Carlo and mean-field studies on the magnetic properties of a hexagonal Ising nanowire with core-shell structure in the Blume–Emery–Griffiths model

The mean-field approximation based on the Gibbs-Bogoliubov inequality and Monte Carlo simulations based on the Metropolis method in the Blume–Emery–Griffiths model were used to successfully examine a hexagonal Ising nanowire with spin-1. It was found that the model displays fascinating phase diagrams in various planes of interest by using both methods. The investigation of magnetic hysteresis cycles also exhibits interesting properties. The model not only presents first- and second-order phase transition lines, but also the tricritical and isolated critical points, multi-compensation temperatures, and magnetic hysteresis behavior with one to eight cycles.

Mean-field study of magnetic properties and hysteresis behavior in a bilayer graphene Ising system

Using the mean-field approximation based on the Gibbs-Bogoliubov inequality for the free energy, we conducted an investigation into the magnetic properties and hysteresis behavior of a graphene Ising bilayer, where the top and bottom layers are occupied by spins σ = 3/2 and S = 5/2, respectively. The effects of exchange interactions, crystal fields, external magnetic field and temperature on the total magnetization, partial magnetizations of each layer, total magnetic susceptibility, blocking temperature and hysteresis loops of the system were thoroughly analyzed. The variations of the blocking temperature as a function of various parameters in the system’s Hamiltonian were presented. Furthermore, we demonstrated the existence of multiple hysteresis loop behaviors under specific physical conditions.

Strain-induced magnetic anisotropy of multi-domain epitaxial EuPd2 thin films

Europium intermetallic compounds show a variety of different ground states and anomalous physical properties due to the interactions between the localized 4f electrons and the delocalized electronic states. Europium is also the most reactive of the rare earth metals which might be the reason why very few works are concerned with the properties of Eu-based thin films. Here we address the low-temperature magnetic properties of ferromagnetic EuPd2 thin films prepared by molecular beam epitaxy. The epitaxial (111)-oriented thin films grow on MgO (100) with eight different domain orientations. We analyze the low-temperature magnetic hysteresis behavior by means of micromagnetic simulations taking the multi-domain morphology explicitly into account and quantify the magnetic crystal anisotropy contribution. By ab initio calculations we trace back the microscopic origin of the magnetic anisotropy to thin film-induced uniform biaxial strain.

A proof-of-concept Bitter-like HTS electromagnet fabricated from a silver-infiltrated (RE)BCO ceramic bulk

A novel concept for a compact high-field magnet coil is introduced. This is based on stacking slit annular discs cut from bulk rare-earth barium cuprate ((RE)BCO) ceramic in a Bitter-like architecture. Finite-element modelling shows that a small 20 turn stack (with a total coil volume of < 20 cm3) is capable of generating a central bore magnetic field of > 2 T at 77 K and > 20 T at 30 K. Unlike resistive Bitter magnets, the high-temperature superconducting (HTS) Bitter stack exhibits significant non-linear field behaviour during current ramping, caused by current filling proceeding from the inner radius outwards in each HTS layer. Practical proof-of-concept for this architecture was then demonstrated through fabricating an uninsulated four-turn prototype coil stack and operating this at 77 K. A maximum central field of 0.382 T was measured at 1.2 kA, with an accompanying 6.1 W of internal heat dissipation within the coil. Strong magnetic hysteresis behaviour was observed within the prototype coil, with ≈30% of the maximum central field still remaining trapped 45 min after the current had been removed. The coil was thermally stable during a 15 min hold at 1 kA, and survived thermal cycling to room temperature without noticeable deterioration in performance. A final test-to-destruction of the coil showed that the limiting weak point in the stack was growth-sector boundaries present in the original (RE)BCO bulk.

High magnetoelectric coupling in piezoelectric modified BNT and magnetic NZFO particulate composite

Lead-free magnetoelectric (ME) particulate composite comprising piezoelectric 72.5Bi0·5Na0·5TiO3-22.5Bi0·5K0·5TiO3–5BiMg0·5Ti0·5O3 (MBNT) and piezomagnetic Ni0·7Zn0·3Fe2O4 (NZFO) in varying phase fraction, i.e., (1-x)MBNT-xNZFO (x = 0.05–0.30; Δx = 0.05) was prepared by solid state reaction route. Their structural, electrical, magnetic and ME properties were investigated. The high temperature sustainability up to 390 °C and the relaxor behavior was confirmed by their dielectric study. The room temperature dielectric constant (∼1081 at 1 kHz), saturation polarization (∼37.12 μC/cm2) and electro-strain (∼0.22 %) was observed maximum for pure MBNT, which decreases in composites with the induction of non-ferroelectric NZFO content. All composites exhibited magnetic hysteresis behavior where net increase in magnetization was associated with the relative increase in NZFO that possessed a saturation magnetization of 74.52 emu/g. At the optimum phase fraction of composite (i.e., 0.80MBNT-0.20NZFO), giant ME coefficient (∼58.12 mV/cm.Oe at 800 Oe) was observed at low frequency of 10 Hz, which suggest its credibility for energy harvester.

Impact of soft magnetic α‐Fe in hard Nd2Fe14B magnetic materials: A micromagnetic study

AbstractThe striving for the independence of fossil energy sources by further development of renewable energies as well as the change in mobility act as a driving force on technological innovations. Magnetic materials with improved magnetic efficiency help to push the limits for optimized, low‐loss power conversion applications and electrification. Besides improving the chemical composition, that is, gaining better performance using alloys reduced or free of heavy rare earth elements, microstructure optimization has proven to be a crucial field of research. In order to better control the grain size, phase distribution and texture of the polycrystalline material, new process routes, such as severe plastic deformation, need to be investigated and explored in addition to the state‐of‐the‐art method – sintering. Here, attention must be paid to the possible formation of soft magnetic α‐Fe after the casting process prior to the actual deformation step, as these secondary phases negatively affect the hysteretic behavior of the magnet. Assistance in the analysis of the underlying magnetic mechanisms is provided by micromagnetic theory. Besides the reliable prediction of the magnetization distribution on micron‐scale, especially in a multi‐phase microstructure, it also allows for the analysis of the magnetic hysteresis behavior. This work provides a micromagnetic simulation frame work based on a finite element scheme. Relying on this framework the effective hysteresis behavior of two different heterogeneous microstructures (Nd2Fe14B and Nd2Fe14B/α‐Fe) are analyzed and compared.

Magnetic properties and hysteresis behavior of a mixed spin-3/2 and spin-3 Ising ferrimagnetic system in a graphene monolayer

Using the mean field approximation (MFA), we have successfully investigated the magnetic properties of the mixed spin Sj=±3,±2,±1,0 and σi=±32,±12 Ising ferrimagnetic system in a graphene layer. The effects of different physical parameters, namely exchange interactions, anisotropies, external field and temperature on the critical, first-order, compensation and hysteresis behaviors have been examined. The results show that, for specific values of these parameters, interesting phenomena appeared, such as compensation and multi-loop hysteresis behavior. It was shown that the compensation phenomenon only occurs if the exchange interaction JA (interaction between spins σi), is greater than a certain minimum value JAmin. We have also shown that, for fixed values of the anisotropies, the relation between JAmin and the exchange interaction JB (interaction between Sj), is a linear one. In addition, we found that each of the behaviors mentioned above is sensitive to the change of a certain physical parameter. Finally, we have verified that our results are comparable with those of other works.

Magnetic Properties and Hysteresis Behavior of a Ferromagnetic Spin-3/2 System in a Graphene Monolayer

Magnetic Properties and Hysteresis Behavior of a Ferromagnetic Spin-3/2 System in a Graphene Monolayer

LLG方程式による直流ヒステリシス特性の計算精度に関する諸検討

Quantitative analysis of iron loss taking magnetic hysteresis behavior into account is essential to loss reduction in electric machines. In the previous research, a novel magnetic circuit model, which incorporates a play model and a Cauer circuit, was proposed. Besides, the play model can be derived from dc hysteresis loops calculated by a simplified Landau-Lifshitz-Gilbert (LLG) equation. However, this method cannot necessarily calculate dc hysteresis loops with high accuracy in all cases so that there is potential for further improvement in its calculation accuracy. Therefore, in this paper, the calculation accuracy of the simplified LLG equation is examined in detail under various conditions.

Boosting the mono-axial crystal field in stable high-coordinate Dy(III) single-ion magnets by substitution of the phenoxy axial ligand.

Synthesis of air-stable and high-performance single-molecule magnets (SMMs) is challenging. Here, a heptadentate pentapyridyldiamine (BPA-TPA) ligand and fine-tuned axial phenoxy ligands are used to synthesize two triangular dodecahedral Dy(III) complexes [Dy(BPA-TPA)(4-methoxy-PhO)](BPh4)2·3CH2Cl2 (4) and [Dy(BPA-TPA)(2,4-dimethyl-PhO)](BPh4)2·0.85CH2Cl2 (5). Both complexes have high effective barriers exceeding 400 K and magnetic hysteresis up to 8 K, which is ascribed to one strong and short Dy-O bond combined with seven weak Dy-N bonds. Ab initio calculations reveal the thermally activated quantum tunneling of magnetization through the first excited Kramers doublet, due to the presence of a strong axial Dy-O crystal ligand. Substitution of the phenoxy ligand leads to more constrained vibrations, improving the magnetic hysteresis behavior for 5.

Experimental Consideration on Influence of Magnetic After Effect on Gap Magnetic Field and Applicability of Conventional Hysteresis Models for Particle Accelerator Electromagnets

AbstractTo further improve the control accuracy of the magnetic field generated by particle accelerator electromagnets, it is necessary to model not only the magnetic hysteresis behavior but also the magnetic after effect, which has never been studied in the previous literature. In this paper, the gap magnetic field of an accelerator magnet was measured under various excitation conditions to acquire the experimental data required for modeling. Consequently, it was clarified that the magnetic after effect may influence the magnetic hysteresis behavior. Moreover, it was accordingly indicated that a novel modeling technique is required in addition to the conventional hysteresis models developed in the electric machine field. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Prediction of magnetic properties of a single-molecule magnetic metallofullerene cluster DySc2N@C80

In this work, we proposed a particle swarm optimization algorithm combined with Monte Carlo simulation method to investigate the magnetic properties of a single-molecule magnetic metallofullerene cluster DySc2N@C80. Based on the experimental results, we estimated the values of the exchange coupling and the anisotropy of the present system according to the critical temperature TC, which achieved a good agreement between simulated and experimental results. In addition, we also obtained the influence of size effect, the curves of magnetization, magnetic susceptibility and internal energy induced by external magnetic field and hysteresis behaviors at different temperatures.

Effects of phosphorus doping on the physical properties of axion insulator candidate EuIn2As2

We report an investigation on the single crystal growth, magnetic and transport properties of EuIn2(As1−x P x )2 (0 ≤ x ≤ 1). The physical properties of axion insulator candidate EuIn2As2 can be effectively tuned by P-doping. With increasing x, the c-axis lattice parameter decreases linearly, the magnetic transition temperature gradually increases and ferromagnetic interactions are enhanced. This is similar to the previously reported high pressure effect on EuIn2As2. For x = 0.40, a spin glass state at T g = 10 K emerges together with the observations of a butter-fly shaped magnetic hysteresis and slow magnetic behavior. Besides, magnetic transition has great influence on the charge carriers in this system and negative colossal magnetoresistance is observed for all P-doped samples. Our findings suggest that EuIn2(As1−x P x )2 is a promising material playground for exploring novel topological states.

Effect of the Transition Metal Ions on the Single-Molecule Magnet Properties in a Family of Air-Stable 3d-4f Ion-Pair Compounds with Pentagonal Bipyramidal Ln(III) Ions.

Single-molecule magnets (SMMs) are expected to be promising candidates for the applications of high-density information storage materials and quantum information processing. Lanthanide SMMs have attracted considerable interest in recent years due to their excellent performance. It has always been interesting but not straightforward to study the relaxation and blocking mechanisms by embedding 3d ions into 4f SMMs. Here we report a family of air-stable 3d-4f ion-pair compounds, YFe (1), DyCr (2), DyFe (3), DyCo (4), and Dy0.04Y0.96Fe (5), composed of pentagonal bipyramidal (D5h) LnIII cations and transition metallocyanate anions. The ion-pair nature makes the dipole-dipole interactions almost the only component of the magnetic interactions that can be clarified and analytically resolved under proper approximation. Therefore, this family provides an intuitive opportunity to investigate the effects of 3d-4f and 4f-4f magnetic interactions on the behavior of site-resolved 4f SMMs. Dynamic magnetic measurements of 1 under a 4 kOe external field reveal slow magnetic relaxation originating from the isolated [FeIII]LS (S = 1/2) ions. Under zero dc field, compounds 2-5 show similar magnetic relaxation processes coming from the separated pentagonal bipyramidal (D5h) DyIII ions with high Orbach barriers of 592(5), 596(4), 595(3), and 606(4) K, respectively. Comparatively, both compounds 3 and 5 exhibit two distinct relaxation processes, respectively from the [FeIII]LS and DyIII [Ueff = 596(4) K for 3 and 610(7) K for 5] ions, under a 4 kOe dc field. The dipolar interactions between the neighboring TMIII (TM = transition metal, CrIII or [FeIII]LS) and DyIII ions were revealed to have little effect on the thermal relaxation in compounds 2, 3, and 5, or the coexistence of the two separate relaxation processes in compounds 3 and 5 under a 4 kOe dc field, but they significantly affect the quantum tunneling of magnetization and the magnetic hysteresis behavior of 2 and 3 at low temperatures compared to those of 4.

Appearance of inverted hysteresis, pinning effect in amorphous FeCoB ribbon with annealing: A Kerr microscopy investigation

A systematic investigation has been carried out on the magnetic domain evolution and local hysteresis behavior in iron based amorphous ribbons (FeCoB) by Kerr microscopy with annealing. Explicitly, we have studied the ‘stress’ magnetic domain structure at the strained region of the ribbon, which is likely to be caused by local residual stress present in the ribbon. It is observed that the stress magnetic domain pattern gradually vanishes at elevated annealing temperature due to thermally relieving of compressive stress. Interestingly, in the same region of the ribbon, but at different ranges of temperature annealing, we have encountered different magnetic domains mechanisms and hysteresis behavior, namely domain wall pinning, inverted hysteresis behavior, and domain wall propagation. The results are explained in terms of competition between different source of anisotropy in the ribbon emerging at different annealing temperature.

Analysis on the microstructure and magnetic properties of MgGaFeO4 spinel compound

AbstractThe single phase of the spinel ferrite MgGaFeO4 is successfully prepared by the high‐temperature solid‐state reaction. The crystal structure, cation distribution, valence state, and magnetic properties are systematically investigated through various techniques in this work. From the analysis of X‐ray diffraction, the face‐centered cubic structure with the space group Fd3m for the single‐phase sample is obtained. The magnetic hysteresis loops M(H) shows a typical magnetic hysteresis behavior at 5 K, while an obvious paramagnetic behavior can be observed at room temperature. The characteristics of magnetic properties suggest that the intrinsic ferromagnetic (FM) interaction and magnetic frustration are cooperated in the system. The specific divergence and irreversibility in the temperature‐dependent magnetization curves M(T) indicate a typical spin‐glass (SG) behavior, which occurring around the freezing temperature Tf = 40 K. Further analysis of the isothermal remanent magnetization (MIRM) suggests the existence of an intensive magnetic frustration state, which leads to stable residual magnetization without decaying under a long time span. More than that, based on the corresponding fitting parameters (τ0 = 8 × 10−12 s, zv = 6.32 and T0 = 56.2 K), the SG state in the sample is further confirmed. The following detailed analyses reveal that the competitions between antiferromagnetic (AFM) and ferromagnetic (FM) interactions definitely exist in MgGaFeO4, which should be the response to motivate the SG behavior.

Plausible multiferroic and magneto-electric behaviour of polycrystalline Bi0.85Gd0.05La0.1FeO3 at room temperature

The structural, magnetic and magneto-electric (ME) properties of polycrystalline BiFeO3 and Bi0.9–xGdxLa0.1FeO3 (x = 0.00 and 0.05) samples have been investigated. X-ray diffraction patterns confirm the formation of single phases in all the samples with ‘R3c’ space group. Magnetic anisotropy and ferroelectric hysteresis behaviour are observed in Bi0.85Gd0.05La0.1FeO3 through magnetization and polarization measurements respectively. In addition, the same compound shows weak ferromagnetism at room temperature with a significantly enhanced remnant magnetization of ~ 23.6emu.mol−1, concomitant with an exchange bias. ME measurements on the compound show a non-linear dependence of magnetic and electric vectors.