Behavior Of Magnetic Materials Research Articles

Unraveling dynamic Jahn-Teller effect and magnetism in FeTiF6×6H2O single crystal

Hydrated iron fluoridotitanate (FeTiF6 × 6 H2O) single crystals are fascinating magnetic materials with unique properties. To understand the underlying mechanisms, this study combines X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques, complemented by density functional theory (DFT) calculations. Polarization-dependent X-ray absorption spectroscopy, encompassing XANES and XMCD, is a powerful technique for probing the local structures and magnetic properties of materials. It is element-selective, bulk-sensitive, and compatible with a wide range of experimental conditions. In this study, we used XANES and XMCD spectroscopies to investigate the local structures and magnetic properties of Fe and Ti in FeTiF6 × 6 H2O single crystals. XANES analysis revealed distinct local environments around Fe and Ti, providing insights into their coordination environments. Element-selective magnetization measurement at the Fe K-edge demonstrated that iron sites in the oxidation state Fe2+ have an unambiguous paramagnetic contribution to the magnetization along the b-axis. Notably, the absence of an XMCD signal at the Ti K-edge confirmed the absence of a magnetic moment in Ti atoms within the crystal. DFT calculations corroborate the experimental findings and provide insights into the electronic structure and magnetic interactions. The combined results provide a comprehensive understanding of the dynamic Jahn-Teller effect in FeTiF6 × 6 H2O single crystals, highlighting the significance of polarization-dependent X-ray absorption spectroscopy in unraveling the intricate magnetic behavior of such materials. This study contributes to the fundamental understanding of magnetism in these materials and paves the way for the development of novel magnetic materials with tailored properties.

Deep learning model for enhanced power loss prediction in the frequency domain for magnetic materials

AbstractThis paper outlines the methodology for predicting power loss in magnetic materials. It starts by introducing the concept of core loss and the complexity of modelling it. Steinmetz's equation is presented to calculate power loss based on frequency and magnetic flux density, but its limitations are highlighted. As an alternative, a neural network‐based method is introduced. The proposed methodology adopts a long short‐term memory network, expressing the core loss as a function of magnetic flux density, frequency, temperature, and wave classification. Fast Fourier transform was implemented to reduce the data points of the sampled flux density waveform while preserving its characteristics. Analyzing in the frequency domain enabled streamlining the training of the model. The input features were arranged as required, and the network architecture was designed with appropriate layers and optimal activation functions. Through extensive training using the datasets, the model assimilated intricate relationships between input variables and known power loss. Evaluation and validation metrics were subsequently employed to gauge the performance of the trained network. This innovative methodology aims to significantly augment the precision of power loss predictions, providing valuable insights into the nuanced behaviour of magnetic materials.

Effect of aging on temperature dependence of FeCuSiNbB nanocrystalline materials

Nowadays, increasing energy efficiency in the automotive industry is promoted by employing compact electrical systems. This reduction in the mass and volume of electrical systems exposes magnetic components to high temperatures for extended periods. The present paper investigates the magnetic behavior of FeCuSiNbB nanocrystalline materials across various temperature ranges. Subsequently, the temperature dependency is reevaluated after exposing the magnetic cores to aging at 200 °C. The entire study is founded on monitoring the evolution of macroscopic magnetic properties and analyzing anisotropic energies.

Physical properties of ferromagnetic Mn-doped double perovskites (DPs) Cs2AgInCl/Br6 for spintronics and solar cell devices: DFT calculations.

A computational framework based on density functional theory (DFT) has been effectively employed to investigate the wide-ranging physical characteristics of ferromagnetic manganese (Mn)-substituted double perovskites (DPs) with composition Cs2AgIn1-xMnxCl/Br6 (x = 0.0, 0.25). This research covers a systematic exploration of the mentioned DPs for potential applications in the domains of spintronics and energy conversion devices. The physics concerning ferromagnetic (FM) Cs2AgIn0.75Mn0.25Cl/Br6 DPs was studied computationally using the modified Becke-Johnson (mBJ-LDA) potential and the generalized gradient approximation (PBEsol GGA) method introduced by Perdew, Burke, and Ernzerhof. The structural, electronic, magnetic, and transport behavior of materials were investigated using these computations. Structural parameters for both perovskite materials were computed subsequent to their optimization in FM phase. According to evaluations of the electronic band structure and density of states (DOS), the incorporation of Mn ions into the host lattice causes exchange splitting induced by p-d hybridization, consequently stabilizing the FM state. Probing the sharing of magnetic moment, charge, and spin between the substituent cations and the host anions led to the comprehensive elaboration of this exchange splitting of bands. Important parameters such as exchange constants (N0α, N0β), and direct spin-exchange splitting Δx(d), support the stability of the FM state. Finally, we briefly explored the spin effect on other aspects of electronic transport, the Seebeck coefficient, and the power factor, using the conventional Boltzmann transport theory.

An efficient multi-objective optimization strategy for Halbach array permanent magnet synchronous machines based on nonlinear semi-analytical model

In this article, an efficient multi-objective optimization strategy for the Halbach array permanent magnet synchronous machine (PMSM) is developed by taking into consideration the nonlinear B-H behavior of soft magnetic materials. Based on the harmonic modeling (HM) technology, the electromagnetic performances (EPs) of the Halbach array PMSM can be computed. To specifically model the local magnetic saturation, the stator teeth are separated into several annular layers, and each tooth is further divided into several regions along the tangential direction. Then, the parameters of the Halbach array PMSM are optimized utilizing combined nonlinear semi-analytical model (SAM) and non-dominated sorting genetic algorithm II (NSGA-II). To validate the effectiveness and accuracy of the developed optimization scheme, a Halbach array prototype is then manufactured in accordance with the optimization results. The multi-objective rapid optimization strategy developed in this article, which includes but is not limited to Halbach array permanent magnet (PM) machines, serves as a reference for the design and optimization of various PM machines.

Comparative Study of Magnetic Properties of (Mn1−xAxIV)Bi2Te4 AIV = Ge, Pb, Sn

We investigated the magnetic properties of the antiferromagnetic (AFM) topological insulator MnBi2Te4 with a partial substitution of Mn atoms by non-magnetic elements (AIV = Ge, Pb, Sn). Samples with various element concentrations (10–80%) were studied using SQUID magnetometry. The results demonstrate that, for all substitutes the type of magnetic ordering remains AFM, while the Néel temperature (TN) and spin-flop transition field (HSF) decrease with an increasing AIV = Ge, Pb, Sn concentration. The rate of decrease varies among the elements, being highest for Pb, followed by Sn and Ge. This behavior is attributed to the combined effects of the magnetic dilution and lattice parameter increase on magnetic properties, most prominent in (Mn1−xPbx)Bi2Te4. Besides this, the linear approximation of the experimental data of TN and HSF suggests higher magnetic parameters for pure MnBi2Te4 than observed experimentally, indicating the possibility of their non-monotonic variation at low concentrations and the potential for enhancing magnetic properties through doping MnBi2Te4 with small amounts of nonmagnetic impurities. Notably, the (Mn1−xPbx)Bi2Te4 sample with 10% Pb substitution indeed exhibits increased magnetic parameters, which is also validated by local-probe analyses using ARPES. Our findings shed light on tailoring the magnetic behavior of MnBi2Te4-based materials, offering insights into the potential applications in device technologies.

A Comparison of the magnetic characteristics and exchange spring effect of Y-substituted Co2Mn1-xYxO4 composite spinel oxides

Magnetic spinel oxides are materials that exhibit unique magnetic properties due to their crystal structure and composition. Herein, we report the sol-gel synthesis of Y-substituted Co2Mn1-xYxO4 (0 ≤ x ≤ 0.1) inverse spinel oxides. X-ray diffraction pattern confirms the single-phase cubic structure with space group Fd3m. Magnetic susceptibility measurement results exhibited the para-ferrimagnetic phase transition near TC = 174 K. Also, another phase transition near a specific temperature T* = 76 K, below TC of Y-doped samples. Furthermore, the magnetic entropy change analysis also confirmed the magnetic phase transition near the temperature of T*. Moreover, with the phase transition near T*, Y-doped samples show magnetic anomalies at low temperatures. Similarly, the analysis of magnetic entropy change and the magnetic hysteresis loops show the coexistence of “soft " and “hard” ferromagnetic phases at low temperatures in Y-substituent Co2Mn1-xYxO4 samples. Using the coupling of the “soft/hard” ferromagnetic phase boundary, a noticeable exchange spring effect can be observed at low temperatures. Due to the exchange spring effect, the magnetic energy product (BH)max up to 3.1 MJ m−3 can be obtained at 2 K. Such insights can help to optimize the behavior of magnetic materials and structures, leading to improved performance and functionality in applications such as magnetic data storage, magnetic sensors, spintronics, and magnetic nanoparticles.

Bioactive Magnetic Materials in Bone Tissue Engineering: A Review of Recent Findings in CaP‐Based Particles and 3D‐Printed Scaffolds

Diverse applications of nanoparticles (NP) have been revolutionary for various industrial sectors worldwide. In particular, magnetic nanoparticles (MNP) have gained great interest because of their applications in specialized medical areas. This review starts with a brief overview of the magnetic behavior of MNP and a short description of their most used synthesis methods. The second part is dedicated to the MNP applications in tissue engineering, emphasizing the calcium phosphate‐based NP with intrinsic magnetic properties, recently highlighted in the literature as alternative and viable solutions for bone regeneration. The challenges associated with the controversial long‐term toxicity effects of MNP can be overcome using this new generation of multifunctional bone‐like magnetic materials. Furthermore, the influence of magnetic field parameters, such as modality of application, intensity, and spatial distribution, on the biological behavior of magnetic materials, especially for bone repair, is shown. The last part of the review presents the current state of the art regarding the development of magnetic biomaterials for additive manufacturing (AM), aiming to fabricate scaffolds by AM technologies, focusing on bone tissue engineering applications.

Stability and magnetic behavior of exfoliable nanowire one-dimensional materials

Stability and magnetic behavior of exfoliable nanowire one-dimensional materials

Magneto-Mechanical and Thermal Properties of Nd-Fe-B-Epoxy-Bonded Composite Materials.

Polymer-bonded magnets are a class of composite material that combines the magnetic properties of metal particles and the molding possibility of a polymeric matrix. This class of materials has shown huge potential for various applications in industry and engineering. Traditional research in this field has so far mainly focused on mechanical, electrical or magnetic properties of the composite, or on particle size and distribution. This examination of synthesized Nd-Fe-B-epoxy composite materials includes the mutual comparison of impact toughness, fatigue, and the structural, thermal, dynamic-mechanical, and magnetic behavior of materials with different content of magnetic Nd-Fe-B particles, in a wide range from 5 to 95 wt.%. This paper tests the influence of the Nd-Fe-B content on impacting the toughness of the composite material, as this relationship has not been tested before. The results show that impact toughness decreases, while magnetic properties increase, along with increasing content of Nd-Fe-B. Based on the observed trends, selected samples have been analyzed in terms of crack growth rate behavior. Analysis of the fracture surface morphology reveals the formation of a stable and homogeneous composite material. The synthesis route, the applied methods of characterization and analysis, and the comparison of the obtained results can provide a composite material with optimum properties for a specific purpose.

Dynamics of damped and undamped wave natures in ferromagnetic materials

In this paper, a wide range of new exact solutions of the Kraenkel–Manna–Merle (KMM) system is investigated. To study this, we have considered two analytical methods namely the new sub-equation (NSE) method and modified Khater’s (mK) method. The obtained solutions result in distinct wave natures for different numerical parameters and in the presence and absence of a damping factor. These are anti-peakon, three-soliton propagation, mixed soliton-anti-kink, mixed two-soliton-anti-kink, two bright soliton propagation, anti-kink, a grey-type periodic wave, periodic, dark, bright, grey, bright periodic, u-shaped periodic and evolving wave shape solutions. Graphical representations are made in order to carefully examine and analyse these dynamical characteristics of the derived solutions. Additionally, these wave properties are very useful in explaining the behaviour of magnetic materials both in the absence and presence of damping factor. Furthermore, it can be helpful in discussing additional uses of magnetic materials in various aspects.

Deep learning-based wave digital modeling of rate-dependent hysteretic nonlinearities for virtual analog applications

Electromagnetic components greatly contribute to the peculiar timbre of analog audio gear. Indeed, distortion effects due to the nonlinear behavior of magnetic materials are known to play an important role in enriching the harmonic content of an audio signal. However, despite the abundant research that has been devoted to the characterization of nonlinearities in the context of virtual analog modeling over the years, the discrete-time simulation of circuits exhibiting rate-dependent hysteretic phenomena remains an open challenge. In this article, we present a novel data-driven approach for the wave digital modeling of rate-dependent hysteresis using recurrent neural networks (RNNs). Thanks to the modularity of wave digital filters, we are able to locally characterize the wave scattering relations of a hysteretic reluctance by encapsulating an RNN-based model into a single one-port wave digital block. Hence, we successfully apply the proposed methodology to the emulation of the output stage of a vacuum-tube guitar amplifier featuring a nonlinear transformer.

Regulating the reaction pathway of nZVI to improve the decontamination performance through magnetic spatial confinement effect

Nanoscale zero-valent iron (nZVI) shows high effectiveness in the catalyzed removal of contaminants in wastewater treatment. However, the uncontrolled interfacial electron transfer behavior and formation of surface iron oxide (FeOx) layer led to severe electron wasting and occasionally form highly toxic intermediates. Here, we constructed magnetic mesoporous SiO2 shell on surface of nZVI to stimulate a magnetic spatial confinement effect and regulate the electron transfer pattern. Therein, Fe atom facilely spread out from the nZVI core, orderly release electron to surface adsorbed H2O molecule, which is efficiently transformed into active hydrogen (H*). Meanwhile, in-situ Raman revealed that Fe atoms were involved in the formation of penetrable γ-FeOOH rather than FeOx layer, enabling the continuous inward diffusion of H2O and outward diffusion of H* . Employing the catalyzed removal of halogenated phenols as demo reaction, the presence of magnetic mesoporous SiO2 shell utilized the reaction between electrons and H2O to switch the reaction pathway from the reduction/oxidation hybrid process to hydrodehalogantion, and increased the conversion of halogenated phenols-to-phenols by 5.53 times. This study shows the forehand of improving the decontamination performance of nZVI through sophisticated designed surface coating, as well as fine regulating the environmental behavior of magnetic material via micro-magnetic field.

Investigation of Rotational Magnetization Under Non-Sinusoidal Excitation for Non-Oriented Material

Rotational loss forms a significant portion of total core losses in electrical machines. The influence of harmonics on the behavior of magnetic materials is inevitable as these machines are mostly supplied by power electronic converters. Minor loops in hysteresis curves due to harmonics lead to additional losses. While the case of alternating induction (1-D magnetization) with harmonics is thoroughly considered in the literature, the assessment of the effect of rotational magnetization (2-D magnetization) has not yet been done adequately. A qualitative evaluation of rotational hysteresis loops in the presence of minor loops is carried out. The impact of minor loops in the evolution of hysteresis loops under rotating fields is examined. A peculiar behavior of interleaving of hysteresis loops under rotational magnetization is observed, which will affect the total core loss. This analysis can be used to visualize flux patterns on account of rotational magnetization and to accurately predict the performance of a machine during its predesign stage.

Direct imaging of stress-induced magnetic behavior transitions

Stress induction plays a special role in performance control for material science. So far, it has remained challenging to systematically investigate magnetoelectric effect under stress-mediated interaction. Here we constructed a magnetoelectric device with piezoelectric stress induction, in which the stress plays a crucial intermediate role during the controllable modification of the magnetic behavior transitions under the magnetic field or current pulse driven process. The compressive stress was found to make the above process easier and reduce energy consumption via changing the magnetic domain energy state. Meanwhile, both the domain distribution and domain-wall driven process are sensitive to stress intensity. Our magnetoelectric device integrated the advantages of voltage-stress and spin-current for the control of magnetic behavior transition with the help of micro-nano processing. For the stress-induced magnetic behavior in magnetic materials was directly imaged and quantificationally investigated, the complex interactions between stress, magnetic domain motion, magnetic field, and spin current have been clarified.

Magnetic field induced ab -plane rotation of the Eu magnetic moments in trigonal EuMg2Bi2 and EuMg2Sb2 single crystals below their Néel temperatures

The thermodynamic and electronic-transport properties of trigonal ${\mathrm{EuMg}}_{2}{\mathrm{Bi}}_{2}$ in $ab$-plane magnetic fields ${\mathbf{H}}_{x}$ and the A-type antiferromagnetic structure have recently been reported. The Eu magnetic moments with spin $S=7/2$ remain locked in the $ab$ plane up to and above the $ab$-plane critical field ${\mathbf{H}}_{x}^{\mathrm{c}}=27.5$ kOe at which the Eu moments become parallel to ${\mathbf{H}}_{x}$. Here additional measurements at low fields are reported that reveal a new spin-reorientation transition at a field ${H}_{c1}\ensuremath{\approx}465$ Oe where the Eu moments remain in the $ab$ plane but become perpendicular to ${H}_{x}$. At higher fields, the moments cant toward the field resulting in $M\ensuremath{\propto}{H}_{x}$ up to ${\mathbf{H}}_{x}^{\mathrm{c}}$. Similar results are reported from measurements of the magnetic properties of ${\mathrm{EuMg}}_{2}{\mathrm{Sb}}_{2}$ single crystals, where ${H}_{\mathrm{c}1}\ensuremath{\approx}220$ Oe is found. Theory is formulated that models the low-field magnetic behavior of both materials, and the associated anisotropies are calculated. The $ab$-plane trigonal anisotropy in ${\mathrm{EuMg}}_{2}{\mathrm{Sb}}_{2}$ is found to be significantly smaller than in ${\mathrm{EuMg}}_{2}{\mathrm{Bi}}_{2}$.

Research and Analysis on Design Characteristics of High-Speed Permanent Magnet Claw Pole Motor With Soft Magnetic Composite Cores for Wide Temperature Range

As the operating temperature of the motor increases, the material properties will be seriously affected, such as soft magnetic materials, hard magnetic materials, and winding insulation properties. For high-speed permanent magnet motors, the higher loss density and smaller heat dissipation area make the impact of temperature more serious. However, according to the test standard, the magnetic properties are usually measured at room temperature, ignoring the effect of temperature. To accurately design magnetic devices, it is necessary to understand the behavior of magnetic materials at different temperatures. In this article, a new high-speed permanent magnet claw-pole motor with soft magnetic composite for a wide temperature range is proposed. The design process mainly includes the calculation and analysis of material temperature characteristics, bearing support, topological structure, rotor stress calculation, and so on. Finally, a prototype is manufactured and tested to verify the design process.

Theoretical Study of Magnon Spin Currents in Chromium Trihalide Hetero-bilayers: Implications for Magnonic and Spintronic Devices

The intriguing magnetic behavior of two-dimensional chromium trihalide materials holds great promises for spintronics and magnonics. Here, we study the stacking-dependent magnetism in (CrBr3/CrI3) hetero-bilayers by using first-principles calculations. We find that different stackings yield ferromagnetic ground states or favor an antiferromagnetic (AFM) interlayer coupling. Starting from ab initio results, we study the magnonic spectra and magnon spin textures in the hetero-bilayer. Based on our findings, we propose an experimental setup for the optical generation and electric detection of pure magnon spin currents in layered AFM (LAFM) (CrBr3/CrI3) hetero-bilayers. Furthermore, we propose a device to simultaneously realize magnon spin currents and topological domain walls in the hetero-bilayers. The advantages of (CrBr3/CrI3) hetero-bilayers over the (CrI3)2 homo-bilayers to realize magnon spin currents are highlighted. The interesting features of magnons in LAFM hetero-bilayers and their potential for spin-charge conversion could pave the way for their implementation in spin-based transistors and logic devices.

Ferrofluid high internal phase emulsion polymer foams for soft, magnetic materials

Magnetic components are an essential part of current electronics, although the materials used to make magnetic components are almost exclusively rigid and non-deformable. The high modulus and inflexible behavior of typical magnetic materials makes their integration into soft, deformable electronics challenging. Soft electronics, however, is a dynamic field pushing forward the state-of-the-art in wearable sensors, human-machine interaction, and biomimetic robots. In order to access the wide range of functionality of rigid electronics, magnetic materials must be made that are high performing and deformable. One previously unexplored route to creating such materials is the encapsulation of a high concentration of magnetic fluids, such as ferrofluids (FF), into an elastomer using high internal phase emulsification. In this work, the formulation factors required to make an effective ferrofluid high internal phase emulsion polymer foam (polyHIPE) utilizing polydimethylsiloxane (PDMS) were investigated such as the emulsifiers, polyHIPE curing kinetics, and the interaction of emulsified nanoparticles. The porous structure, magnetic properties, and mechanical properties of the final, successful FF/PDMS polyHIPE were subsequently characterized. Pores ranged between 10 and 50 μm with visible nanoparticle aggregation. FF/PDMS polyHIPE had an Ms of 18 A∙m2/kg and susceptibility of 0.69, which is reduced as compared to neat ferrofluid, as expected, but an improvement on ferrofluid polymer dispersions found in the literature. Coercivity and magnetic remanence also decreased with respect to the neat ferrofluid. Rheology demonstrated that the polyHIPE had a significantly lower modulus than the neat PDMS as well as a lower modulus than any magnetic composite material currently published. The FF/PDMS polyHIPE created in this work not only demonstrates the potential for deformable magnetic materials based on the emulsification of high concentrations of magnetic fluid into elastomers, but also the potential to create even higher performing materials using a higher concentration of magnetic fluid or ferrofluids with superior magnetic properties.

Thermodynamics of the Nonrelativistic Free-Electron Fermi Gas in One, Two, and Three Dimensions from the Degenerate to the Nondegenerate Temperature Regime

The thermodynamic and electronic-transport properties of trigonal EuMg2Bi2 in ab-plane magnetic fields Hx and the A-type antiferromagnetic structure have recently been reported. At a temperature of 1.8 K < TN, the Eu magnetic moments with spin S = 7/2 remain locked in the ab plane up to and above the ab-plane critical field Hxc = 27.5 kOe at which the Eu moments become parallel to Hx. Here additional measurements at low fields are reported that reveal a new spin-reorientation transition at a field Hc1 = 465 Oe where the Eu moments remain in the ab plane but become perpendicular to Hx. At higher fields, the moments cant towards the field resulting in M proportional to Hx up to Hxc. Similar results are reported from measurements of the magnetic properties of EuMg2Sb2 single crystals, where Hc1 = 220 Oe is found. Theory is formulated that models the low-field magnetic behavior of both materials, and the associated anisotropies are calculated. The ab-plane trigonal anisotropy in EuMg2Sb2 is found to be significantly smaller than in EuMg2Bi2.