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This paper proposes a method to include the anisotropic hysteresis characteristics of soft-magnetic laminated steels in the magnetic equivalent circuit (MEC) modeling. The loop-based MEC formulation is improved to handle the nonlinearity of the anisotropic magnetic hysteresis, including the dynamic classical eddy-current and excess fields. The developed MEC model is coupled with both the single-valued B-H curve (SVC) in magnetostatic and the dynamic vector hysteresis model (VHM) in transient analysis. Results with a single elementary MEC element show that an alternating magnetic field in a single direction with a peak value smaller than 300 A/m causes a discrepancy of more than 10% between the magnetic flux densities calculated by the VHM and SVC at 50 and 200 Hz excitation frequencies. Moreover, the proposed modeling technique is verified experimentally using the laminated transformer core of TEAM problem 32. The induced voltage calculated by the MEC model with the VHM demonstrates a good agreement with the measurements, while the MEC model with the SVC calculates inaccurate voltage waveforms. Lastly, the total iron loss dissipated in the transformer's iron core is investigated to verify the proposed technique under different excitation levels and frequencies up to 500 Hz. It is observed that the proposed MEC model with the vector hysteresis characteristics of laminated steels is able to calculate the iron loss accurately, while the conventional single-valued curve method fails to estimate the iron loss.

In tunnel magnetic Josephson junctions (JJs), we have provided evidence of an inverse magnetic dependence of the critical current Ic(H), i.e., a shift of the Ic(H) curves in the opposite expected direction. We have established a self-consistent method to ascribe this unconventional feature to spin polarization phenomena at the S/F interface. Through a magnetic characterization of Superconductor (S) /Ferromagnet (F) /Superconductor (S) trilayers and a magnetostatic analysis of the devices, we show that the F-stray fields fail to determine the pattern inversion. The comparative analysis with the literature supports our thesis that this phenomenon can be explained in terms of inverse proximity effect and observed with a proper choice of materials and thickness of the ferromagnetic layer involved in the junction structure. More generally, our approach proves that a careful investigation of the magnetic field pattern in magnetic JJs can lead to the detection of novel effects arising at the S/F interface.

The Everett map is a component used by the Preisach model (PM) that stores hysteresis behavior. In magnetics it often contains the characterized magnetic properties of soft-magnetic material. Fundamentally, the Everett map is created from scattered data points, obtained from a set of magnetic measurements, which must be interpolated to obtain a continuous map. The commonly adopted method to perform the interpolation is based on a Delaunay triangulation computation and subsequent polynomial or B-spline surface fit. However, this approach introduces artifacts in the modeled hysteresis results. Therefore, this work presents an alternative method to construct an artifact-free Everett map, by reconstructing a set of measured hysteresis loops with a pre-processing algorithm and representing the data with a scattered B-spline surface. When applied in the PM, a set of test hysteresis loops was reproduced with high accuracy and without artifacts, compared to the commonly used Delaunay-based interpolant.

The table-like magnetocaloric effect is significant for the magnetic refrigeration applications above 20 K based on the Ericsson cycle. Herein, we prepared a series of Nd6Fe13Pd1–xCux (x=0.05, 0.1, 0.15) compounds by the arc-melting method. These compounds show the single crystalline phase in the tetragonal Nd6Fe13Si-type structure with the space group I4/mcm. A magnetic phase transition from ferromagnetism to antiferromagnetism and a metamagnetic transition from the antiferromagnetic state to the ferromagnetic state were observed in each of the compounds. The compounds exhibit table-like magnetocaloric effects with large refrigerant capacities. A constant ΔSM in a temperature span of 40 K in the Nd6Fe13Pd0.85Cu0.15 compound was observed. For a field change of 0–5 T, the peak values of –ΔSM for the Nd6Fe13Pd0.95Cu0.05, Nd6Fe13Pd0.90Cu0.10, and Nd6Fe13Pd0.85Cu0.15 compounds were estimated to be 4.8, 4.6 and 4.4 J/(kg·K) with corresponding refrigerant capacity values of 323, 331 and 316 J/kg, respectively. The obtained table-like magnetocaloric effects with large refrigerant capacities as well as fairly small thermal and magnetic hysteresis deem these series of compounds good candidates for single-phase magnetic refrigeration based on the Ericsson cycle.

Summary Single-molecule magnets (SMMs) are molecules that can retain magnetic polarization in the absence of an external magnetic field and embody the ultimate size limit for spin-based information storage and processing. Multimetallic lanthanide complexes lacking magnetic exchange coupling enable fast relaxation pathways that attenuate the full potential of these species. Employment of diamagnetic heavy main group elements with diffuse orbitals may lead to unprecedented strong coupling. Herein, two bismuth-cluster-bridged lanthanide complexes, [K(THF)4]2[Cp∗2Ln2Bi6] (Cp∗ = pentamethylcyclopentadienyl; 1-Ln, Ln = Tb, Dy), were synthesized via a solution organometallic approach. The neutral [Ln2Bi6] heterometallocubane core features lanthanide centers that are bridged by a rare Bi66− Zintl ion, which supports strong ferromagnetic interactions between lanthanides. This affords the rare observation of magnetic blocking and open hysteresis loops for superexchange-coupled SMMs comprising solely lanthanide ions. Both compounds constitute the first SMMs containing bismuth donors paving the way for promising synthetic targets for quantum computation.

The metastable α”-Fe16N2 is considered to be a candidate for rare earth-free semi-hard magnetic materials. However, it is necessary to improve the magnetocrystalline anisotropy of α”-Fe16N2 to obtain higher coercivity, Hc. Many theoretical calculations and thin film experiments have been performed by the substitution of Fe with elements such as Co, Ni, Mn, and Al. For example, Co is suggested to increase the magnetocrystalline anisotropy. The nitridation of α-Fe nanoparticles produced by the reduction of an iron hydroxide such as α-FeOOH is well known as one method for the synthesis of α”-Fe16N2 nanoparticles. We have previously reported the influence of Co or Al substitution for Fe by the synthesis of α”-(Fe, Co)16N2 or α”-(Fe, Al)16N2 nanoparticles, and revealed that Co substitution results in very narrow limits of the temperature regions for reduction and nitridation, while Al substitution results in wider temperature regions. Here, we attempt the synthesis of α”-(Fe0.95Co0.02Al0.03)16N2 nanoparticles by hydrogen reduction of α-(Fe0.95Co0.02Al0.03)OOH as a starting material and subsequent nitridation to investigate the complex effect of Fe substitution by Co and Al.

In this study, a hysteresis reduction technique for tunneling magnetoresistive (TMR) sensor for low magnetic field sensing is proposed, where a small ac modulation magnetic field is applied. The magnetic tunnel junctions were connected into an asymmetric Wheatstone bridge to form a sensor, and the output voltage of the TMR sensor was measured using a small ac modulation field and test field along the sensor’s sensing direction. The results showed that hysteresis in the TMR sensor can be effectively reduced to exhibit a linear response. Further, the frequency response of the TMR sensor was studied. Finally, the feasibility of the TMR sensor for low-field detection with small ac modulation was demonstrated.

Magnetic field shields are important for electronic equipment, ultrahigh-sensitivity sensors, and electrical instruments. For ultrahigh-sensitivity atomic sensors, in particular, ferrite shields with low intrinsic magnetic noise are widely used. In this article, the calculation methods of longitudinal and transverse magnetic noise, which are calculated by loss, are analyzed. The experimental results confirm the feasibility of the model. Using the loss separation method, it is proved that the loss of ferrite magnetic shielding is mainly hysteresis loss, which is below 100 Hz. To effectively reduce the magnetic noise, we analyze the effect of structure parameters on the longitudinal and transverse magnetic noise, and the optimized parameters are obtained. The results show that the longitudinal magnetic noise decreases with the increasing aspect ratio and stabilize eventually. When the aspect ratio exceeds 1, the transverse magnetic noise remains practically unchanged. When the external diameter is fixed, by optimizing the thickness of the magnetic shield, the optimal solution for the longitudinal and transverse magnetic noise is obtained.

Most permanent magnet (PM) loss studies consider only eddy current loss and neglect hysteresis. In this article, the hysteresis behavior of two NdFeB PM grades with different magnetic properties is assessed when applied in a PMSM. Data from vibrating sample magnetometer measurements and hysteresis modeling are used as a base. In addition to the main magnetic phase, the samples contained magnetic phases with reduced coercivity. Such phases may contribute to hysteresis losses in a PM material. A new model is introduced to simulate the hysteresis of rare-earth magnets of any geometric shape in the second and first quadrants of the intrinsic BH -plane. The magnetic field strength distribution in the PM material of an electrical motor is analyzed by two-dimensional finite-element method. The results are used as the input data for an analytical hysteresis model. The results indicate that the hysteresis loss resulting from the structural imperfections and geometry of the magnet may introduce a considerable loss in NdFeB PMs applied in rotating electrical machines.

Magnetic viscosity experiments have been performed in order to investigate the magnetization reversal in Sr nanoferrite particles (nanoscale SrFe12O19) and interacting Sr/Co nanoferrite particles (SrFe12O19–CoFe2O4 nanocomposites). The magnetic viscosity S = d M ( t ) / d l n ( t ), where M ( t ) is the magnetization as a function of time, has been collected. For Sr nanoferrite S shows a maximum close to the coercive field, reflecting the relation between S and the energy barrier distribution. We evidence that magnetic viscosity experiments on Sr nanoferrite and interacting Sr/Co nanoferrite particles provide reliable qualitative results for the different magnetic field sweep rate and saturating field H s a t considered. In addition, the activation volumes extracted from the magnetic viscosity experiments performed at different temperatures on Sr nanoferrite are quantitatively correlated to anisotropy changes.

In this work, we measured and analyzed the magnetic susceptibility and the isotherms of magnetization of a semimagnetic material based on CdS: Fe with nanosized inclusions of FeS and Fe2O3 phases. These measurements made it possible to divide the ferromagnetic and paramagnetic phases. Measurements of magnetic force microscopy showed manifestations of magnetic properties mainly at the boundaries of CdS grains, which is explained by the predominance of the mechanism of diffusion of iron atoms along the boundaries of crystallites. The displacement of Cd atoms with the formation of FeS or the oxidation of Fe to the state of maghemite occurs at the boundaries of these crystallites., В настоящей работе проведены измерения и анализ изотерм намагниченности и магнитной восприимчивости полумагнитного материала на основе CdS:Fe с наноразмерными включениями фаз FeS и Fe2O3. Данные измерения позволили разделить ферромагнитную и парамагнитную фазы. Измерения магнито-силовой микроскопии показали проявление магнитных свойств в основном на границах зерен CdS, что объясняется преобладанием механизма диффузии атомов железа по границам кристаллитов, где и происходит замещение атомов Cd с образованием FeS или окисление Fe до состояния маггемита.

The numerical modeling of magnetic materials in simulators is a difficult task, above all in real devices with specific excitation. The aim of this work is to compare the accuracy of scalar and vector Preisach models in a well know test benchmark: the TEAM 32 problem. The availability of measured data for this benchmark test and the simple geometry allow us to build hysteresis models and to test them in a 2D finite element analysis (FEA) scheme. The specific numerical formulation of each hysteresis model implemented is described, including the technique for the numerical identification of parameters starting from measured data. The comparison among the models is done in terms of accuracy, but also in terms of easy implementation in the FEA scheme and of computational cost.

This paper studies the properties of the Preisach model and the play model, and compare their similarities. Both are history-dependent hysteresis models that are used to model magnetic hysteresis. They are described as discrete sums of simple hysteresis operators but can easily be reformulated as integral equations of continuous distribution functions using either a Preisach weight distribution function or a play distribution function. The models are mostly seen as phenomenological or mathematical tools but can also be related to friction-like pinning of domain-wall motions, where Rayleigh’s law of magnetic hysteresis can be seen as the simplest case on either the play model or the Preisach model. They are poor at modeling other domain behavior, such as nucleation-driven hysteresis. Yet another hysteresis model is the stop model, which can be seen as the inverted version of the play model. This type of model has advantages for expressions linked to energy and can be related to Steinmetz equation of hysteresis losses. The models share several mathematical properties, such as the congruency property and wiping-out property, and both models have a history of dependence that can be described by the series of past reversal points. More generally, it is shown that the many models can be expressed as Preisach models, showing that they can be treated as subcategories of the Preisach type models. These include the play model, the stop model and also the alternative KP-hysteron model.

An advanced magnetic hysteresis modelling, exploiting the Preisach theory and the neural networks, is applied and discussed for the simulation of the magnetization processes of magnetic components made by laser powder bed fusion. Silicon iron samples with different percentage silicon content are used for the evaluation of the accuracy and reliability of the proposed approach. Measurements of the hysteresis loops and energy losses are compared with the computed results for different magnetization amplitudes and frequency rates. This approach is presented and evaluated here to provide a method for the accurate representation of the magnetization processes and the prediction of energy losses involved in additively manufactured ferromagnetic cores, in order to optimize their energy efficiency along different applications.

Purpose This paper aims to use a history-dependent vector stop hysteresis model incorporated into a two dimensional finite elements (FE) simulation environment to solve the magnetic field problems in electrical machines. The vector stop hysteresis model is valid for representing the anisotropic magnetization characteristics of electrical steel sheets. Comparisons of the simulated results with measurements show that the model is well appropriate for the simulation of electrical machines with alternating, rotating and harmonic magnetic flux densities. Design/methodology/approach The anisotropy of the permeability of an electrical steel sheet can be represented by integrating anhysteretic surfaces into the elastic element of a vector hysteresis stop model. The parameters of the vector stop hysteresis model were identified by minimizing the errors between the simulated results and measurements. In this paper, a damped Newton method is applied to solve the nonlinear problem, which ensures a robust convergence of the finite elements simulation with vector stop hysteresis model. Findings Analyzing the measurements of the electrical steel sheets sample obtained from a rotational single sheet tester shows the importance to consider the anisotropic and saturation behavior of the material. Comparing the calculated and measured data corroborates the hypothesis that the presented energy-based vector stop hysteresis model is able to represent these magnetic properties appropriately. To ensure a unique way of hysteresis loops during finite elements simulation, the memory of the vector stop hysteresis model from last time step is kept unchanged during the Newton iterations. Originality/value The results of this work demonstrates that the presented vector hysteresis stop model allows simulation of vector hysteresis effects of electrical steel sheets in electrical machines with a limited amount of measurements. The essential properties of the electrical steel sheets, such as phase shifts, the anisotropy of magnetizations and the magnetization characteristics by alternating, rotating, harmonic magnetization types, can be accurately represented.

Microwave heating of waste electric arc furnace dust (EAFD) for the purpose of its remediation has been studied extensively. However, these studies considered EAFD as a bulk material without addressing either the relative response of its individual constituents or the specific interactions with either the electric or magnetic fields of an electromagnetic wave. In this work, we present a study of the relative contribution of the electromagnetic wave components to the heating of EAFD constituents using separated electric and magnetic microwave fields. ZnO, ZnFe2O4, Fe3O4, and graphite were found to be the main contributors to the heating of EAFD based on their dielectric properties and heating profiles. ZnO and ZnFe2O4 heated only in the electric field yielding temperatures of 846 and 720 °C after heating for 30 and 40 s, respectively at a power input of 118 ± 12 W. Fe3O4 and graphite, in contrast, heated in both electric and magnetic fields owing to their respective magnetic and conductive nature. It is suggested that the selective magnetic heating of Fe3O4 has significant implications for the selective extraction of zinc and lead through thermal treatment of EAFD with halogenated plastics such as polyvinyl chloride (PVC).

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.

For the investigation of the exchange bias effect and magneto-optical properties of Bi0.8Re0.2(Re = Nd and Sm)FeO3 (BNFO and BSFO) nanofibers were synthesized via the electrospinning technique. The crystal structure was changed from rhombohedral phases of space group R3c before undoping shift to orthorhombic phases of space group Pbam and Pnma after doping of Nd3+ and Sm3+ ions, respectively, by the Rietveld refinement results. Analysis of the magnetic hysteresis loops demonstrated that the remanent magnetization especially coercivity of BNFO and BSFO nanofibers at 10 K and 300 K exhibited obviously variation, which was attributed to the lower temperature suppressed the fluctuation of magneto-caloric and valence state. The XPS and EDS results displayed the Nd3+ and Sm3+ ions were successfully doped into BFO nanofibers. Meanwhile, the lattice distortion induced the suppression of antiferromagnetic ordered spin modulation, which played an important role to enhance the magnetic properties. It was observed that the exchange bias effect (HEB) of BNFO nanofibers was higher than those of BSFO nanofibers. UV–vis spectra measurements revealed the band gap of BNFO and BSFO nanofibers was 1.87 eV and 1.85 eV, respectively, and the absorption edges of BSFO nanofibers occurred a slightly red shift. The MO degradation rates of BNFO and BSFO nanofibers reached about 89.4% and 78.6%, respectively, which could be a potential candidate in photo-electron devices and the semiconductor industry.

To reveal the mechanism of interfacial exchange coupling, the magnetic hysteresis (M-H) loop of Co/BiFeO3 bilayers deposited on (001) LaAlO3 (LAO) substrates by magnetron sputtering was measured. T...

Purpose The magnetic characterization of electrical steel is typically examined by measurements under the condition of unidirectional sinusoidal flux density at different magnetization frequencies. A variety of iron loss models were developed and parametrized for these standardized unidirectional iron loss measurements. In the magnetic cross section of rotating electrical machines, the spatial magnetic flux density loci and with them the resulting iron losses vary significantly from these unidirectional cases. For a better recreation of the measured behavior extended iron loss models that consider the effects of rotational magnetization have to be developed and compared to the measured material behavior. The aim of this study is the adaptation, parametrization and validation of an iron loss model considering the spatial flux density loci is presented and validated with measurements of circular and elliptical magnetizations. Design/methodology/approach The proposed iron loss model allows the calculation and separation of the different iron loss components based on the measured iron loss for different spatial magnetization loci. The separation is performed in analogy to the conventional iron loss calculation approach designed for the recreation of the iron losses measured under unidirectional, one-dimensional measurements. The phenomenological behavior for rotating magnetization loci is considered by the formulation of the different iron loss components as a function of the maximum magnetic flux density Bm, axis ratio fAx, angle to the rolling direction (RD) θ and magnetization frequency f. Findings The proposed formulation for the calculation of rotating iron loss is able to recreate the complicated interdependencies between the different iron loss components and the respective spatial magnetic flux loci. The model can be easily implemented in the finite element analysis of rotating electrical machines, leading to good agreement between the theoretically expected behavior and the actual output of the iron loss calculation at different geometric locations in the magnetic cross section of rotating electrical machines. Originality/value Based on conventional one-dimensional iron loss separation approaches and previously performed extensions for rotational magnetization, the terms for the consideration of vectorial unidirectional, elliptical and circular flux density loci are adjusted and compared to the performed rotational measurement. The presented approach for the mathematical formulation of the iron loss model also allows the parametrization of the different iron loss components by unidirectional measurements performed in different directions to the RD on conventional one-dimensional measurement topologies such as the Epstein frames and single sheet testers.

The magnetic refrigeration (MR) utilizing magnetocaloric effect (MCE) has been recognized as an environmentally friendly and energy efficiency technology. Here we presented the magnetic properties and MCE in Pr-doped La1-xPrxFe12B6 (x=0.05-0.2) itinerant-electron metamagnetic (IEM) compounds. A small amount of Pr doping La site can greatly improve the peak values in the magnetic entropy change ΔSM(T) curves, especially under relatively low magnetic field changes (ΔH). Additionally, the peak temperature increases gradually and the magnetic hysteresis reduces gradually with increasing x. The observed MCE in present La1-xPrxFe12B6 compounds is related to its field-induced first-ordered IEM transition. The peak values of ΔSM for La1-xPrxFe12B6 compounds reach 13.4, 15.4, 12.5 and 13.0 J/(kg K) at TC ~58, 68, 72 and 89 K for x=0.05, 0.10, 0.15 and 0.2 under ΔH of 0-7 T, respectively. The corresponding relative cooling power values are 462.3, 480.7, 372.4 and 375.7 J/kg. The present La1-xPrxFe12B6 compounds could be good candidates for active MR application if the magnetic and thermal hysteresis can be further reduced. The present work indicates that the LaFe12B6-based material system could also exhibit promising magnetocaloric performances.

Accurate simulation of the hysteresis loop is challeng-ing, especially using manufacturer data. Traditional parameter extraction methods (e.g., using optimization algorithm and solving transcendental equation) can extract the static Jiles-Atherton (JA) hysteresis model parameters under an arbitrary condition, but it requires fitting parameters because the model parameters vary with flux density. To reduce the dependence on measurement data, this paper proposes a simple but effective parameter extraction method. Firstly, an identification procedure of minor loop is presented using only static B - P loss curves by investigating the influence of model parameters on hysteresis loop, where the average root-mean-square error of the hysteresis loop is decreased by 4. To estimate the dynamic loss coefficients under DC bias, a calculation method based on the Statistical Theory of Losses (STL) is established by investigating the law of influence of DC bias on hysteresis loss and dynamic loss. The effectiveness of the proposed method is verified.

The magnetic property measurementfor grain oriented (GO) silicon steel sheet under non-sinusoidal excitations (DC bias and harmonic) were conducted based on the experimental platform. Based on the Preisach model, the static hysteresis and loss properties were accurately simulated. Furthermore, an improved loss model was proposed by adjusting the statistical parameter of abnormal loss, which depends on the characteristic quantities of DC bias or harmonic excitations. The simulated dynamic hysteresis loops and iron losses under different non-sinusoidal conditions were compared with the measured ones, and thus the accuracy and generality of the improved model proposed in this paper were verified. In addition, the influences of the harmonic and DC-biasing quantities upon the total losses is investigated.

The Cu-0.5 wt.% Mn alloy is selected as the inter-filament matrix in NbTi superconducting strand with low AC Loss. Three types of NbTi strand with the filament number of 10 800, 12 960 and 33 696 were prepared based on high homogeneity Nb47Ti alloy, pure Nb sheet, high purity oxygen free copper and Cu-0.5 wt.% Mn alloy. Heat treatment with 3-5 intermediate annealings has been applied to increase the Jc of the strands. When the number of annealings increases from 3 to 5, Jc raises from 2295 to 2958 A/mm2 for the 10 800 filament strand, and from ∼2500 to ∼2800 A/mm2 for the 12 960 filament and 33696 filament strands. As the filament number increases from 10800 to 33696, the ‘ n ’ values keep the same level, demonstrating that no “sausage like” or “nodular like” filaments exist in the final strands. When the filament diameter of the strand is reduced from 4.6 μm to 2.6 μm, the hysteresis loss decreased from 42.8 mJ/cm3 to 17.3 mJ/cm3 at ± 3 T&4.2 K. Based on this research, WST has obtained a stable mass production technology of the strands. Using heat treatment with 4 annealings, the different batches of the strands with Jc ranged from 2600 to 2800 A/mm2 have been produced with piece length level of 1-3 kilometer.

In this study, spinel NiCexFe2–XO4 (x = 0.0 - 0.5) nanoparticles (NPs) was synthesized by microwave combustion technique (MCT) utilizing the fuel of Aloe vera plant extract. The establishment of spinel cubic crystal structure was ensured by powder X-ray diffraction (PXRD) technique. The particles like nanostructured morphology were confirmed by high-resolution scanning electron microscope (HRSEM). Energy dispersive X-ray (EDX) studies confirmed the formation of spinel ferrite structure and ensured that no other elements were present. Magnetic parameters such as remanant magnetisation (Mr), coercivity (He) and saturation magnetization (Ms) were calculated from the magnetic hysteresis (M-H) loops, which exhibited ferromagnetic behaviour. The photocatalytic behavior was investigated by visible light treatment for the photocatalytic degradation (PCD) of rhodamine B (Rh-B) dye and the sample NiCe0.3Fe1.7O4 exhibits higher PCD efficiency (93.88%) than other compositions. The antibacterial activities of gram-positive S. aureus, B. subtilis, gramnegative K. pneumonia and E. coli have been investigated using undoped and Ce3+ substituted NiFe2O4 NPs and observed higher activity, which indicated that, they can be used in the bio-medical applications.

This paper presents a modeling approach for estimating the vibration of power transformers based on a magnetostriction model and maxwell stress calculation. The magnetostriction model, accounting for the dynamic hysteresis behavior, is constructed by combining the Becker-Doring crystal magnetostriction model and J-A dynamic hysteresis model. By incorporating the proposed model into the finite-element method (FEM), both the Maxwell stress and the magnetostriction force in each mesh element can be readily obtained simultaneously. To verify the calculation method, the vibration of a three-phase transformer prototype is measured and compared with simulated results. It demonstrated that the proposed method is accurate enough to predict the vibration of power transformers.

Fe-based amorphous magnetic materials are recently attracting strong interests for constructing high-power density and high-efficiency rotating electrical machines due to their attractive properties, such as low core loss and high magnetic saturation. Accurate measurement and modeling of the rotational core losses of the core magnetic materials, and the corresponding patterns of rotating magnetic flux density ( $B$ ) and magnetic field strength ( $H$ ) are important for the analysis and design of electrical machines. This article presents the measurement of rotational core loss of a Fe-based amorphous magnetic material (amorphous 1k101), and its corresponding modelings under two-dimensional (2-D) circularly and elliptically rotating magnetic fields. In addition, an improved and simplified analogical model of rotational hysteresis loss is proposed for such magnetic materials. The circular and elliptical $B$ loci and the corresponding $H$ loci have been investigated to acquire the perception of anisotropy and permeability of the amorphous materials. The proposed theory and models are experimentally verified.

Stainless steel and titanium alloys are common materials for orthopaedic implants. However there is a lack of information and studies on magnetic remanence of implants used in clinical practice. The aims of this study are to investigate the composition and the presence of magnetic remanence for these two orthopaedic implant materials. These two factors may cause implant instability and heat problems as well as degradation of the images quality if the patients undergo magnetic resonance imaging (MRI) examination. The magnetic hysteresis loop and remanence status of stainless steel and titanium alloy orthopaedic implants were investigated with a vibrating sample magnetometer (VSM). Both samples of stainless steel and titanium alloy had been exposed to external magnetic fields up to 1 T (10000 G) and 1.4 T (14000 G), respectively. The compositions of these two orthopaedic implant materials were studied using a scanning electron microscope with energy dispersive X-ray analysis (SEM-EDX). The results of the study demonstrated that ferrous and nickel compositions in stainless steel alloy orthopaedic implants contributed to the residual magnetism, as shown in the hysteresis loop. The titanium alloy orthopaedic implant sample does not contain any ferromagnetic elements. After exposure to a magnetic field, the stainless steel values of retentivity, coercivity and magnetisation are significantly higher compared to those of the titanium alloy. The stainless steel orthopaedic implant sample demonstrates a typical hysteresis loop that suggests the existence of magnetic remanence. In contrast, the titanium alloy orthopaedic implant sample showed no significant remanence phenomenon. By considering the existence of magnetic remanence in the implant is important as potential effect on the MRI image quality.

Prussian blue analogue nanocrystals of the CsINiII[CrIII(CN)6] cubic network with 6 nm size were assembled as a single monolayer on highly organized pyrolytic graphite (HOPG). X-ray magnetic circular dichroism (XMCD) studies, at the Ni and Cr L2,3 edges, reveal the presence of an easy plane of magnetization evidenced by an opening of the magnetic hysteresis loop (coercive field of ≈200 Oe) when the magnetic field, B, is at 60° relative to the normal to the substrate. The angular dependence of the X-ray natural linear dichroism (XNLD) reveals both an orientation of the nanocrystals on the substrate and an anisotropy of the electronic cloud of the NiII and CrIII coordination sphere species belonging to the nanocrystals' surface. Ligand field multiplet (LFM) calculations that reproduce the experimental data are consistent with an elongated tetragonal distortion of surface NiII coordination sphere responsible for the magnetic behavior of monolayer.

M-type, Ba0.4Pb0.6Fe12-xCoxO19 (x = 0.00, 0.10, 0.20, 0.30, 0.40) hexaferrites, synthesized using citrate gel auto combustion method, and heated at 950 °C, 4 h for lossless applications. XRD analysis shows the development of the M-phase, along with PbM and hematite. The microstructural analysis reveals the stacking clusters of hexagonally shaped platelets. TEM image and SAED pattern of x = 0.3 composition shows polycrystalline nature and formed particles observed to fused with neighbouring particles. M − H loops of all samples reveal hard magnetic behaviour and possess multi-domain structure. The maximum saturation magnetization of 55.427 A m2/kg is observed in x = 0.10 composition and coercivity of prepared hexaferrites was found to vary from 0.058 T to 0.390 T. The cobalt substitution has a strong influence on the dielectric properties of prepared hexaferrites. The value of ac conductivity increases with cobalt substitution from x = 0.00 to x = 0.10, and followed by a reduction from x = 0.10 to x = 0.40. The same trend is observed for the dielectric constant. The low value of loss tangent for all compositions shows apt scope for lossless application.

This work introduces a material and method for high-volume, low-temperature, screen printing of self-biased magnetic films made from a composite of M-type strontium ferrite SrFe12O19 (SrM) particles and polydimethylsiloxane (PDMS). The magnetic particles are aligned under a dc magnetic field, while the PDMS is cured at 75 °C, making this fabrication process compatible with semiconductor and printed-circuit-board substrates. Aligned composites with estimated SrM particle volume percentages of 14 vol.%, 20 vol.%, and 27 vol.% are fabricated, as well as an unaligned 14 vol.% composite for comparison. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to examine the structure and composition of the composites. Furthermore, vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements are performed to determine their dc and ac magnetic properties. Results show that the aligned composites have magnetic textures between 1.47 and 1.95, crystalline anisotropies between 1860 and 1960 kA/m, FMR frequencies of 45.5–45.9 GHz, and FMR linewidths between 3400 and 3500 Oe, indicating the potential for these materials in self-biased, non-reciprocal device applications. The analysis identifies that increased particle loading and better particle alignment may further improve these films by decreasing the linewidth.

The integration of complete Boolean logic gate and memory in a single device is imperative to develop future computing systems beyond von Neumann architecture. Specifically, the giant magnetoimpedance (GMI) effect has drawn much attention for the high sensitive magnetic sensor applications; however, its possible application in logic-in-memory devices has been rarely explored. This work studies the butterfly-shaped hysteresis GMI effect in the self-biased magnetic heterogeneous laminate (Ni/Fe25Ni54Co15Si1B5/micro-planar coil/Fe25Ni54Co15Si1B5/micro-planar coil/Fe25Ni54Co15Si1B5/Ni) theoretically and experimentally. The proposed theoretical model based on the nonlinear constitutive model of magnetostrictive material, magnetic charge theory, and Maxwell equations indicates that the permeability of Fe25Ni54Co15Si1B5 ribbon is modulated by the varied remanent magnetostatic field and magnetostrictive stress of neighboring Ni ribbon simultaneously, which demonstrates multilevel remanent magnetoimpedance after the external magnetic field is turned off. This is useful for the nonvolatile multistate memory application. Furthermore, 16 complete nonvolatile Boolean logic functions can be also implemented in a single GMI device within three operation cycles. This study provides a promising candidate for future logic-in-memory architecture.

Magnetic nanoparticles (MNPs) are very attractive components in many biomedical applications, particularly as therapeutic magnetic microcarriers (TMMC) for targeted therapy. Although MNPs can be effectively gathered and transported using external magnetic fields, the optimal delivery is yet to be fully investigated. In this letter, we discuss the modeling and the characterization of deformable soft magnetic microrobots under various magnetic field conditions. The microrobots considered consist of superparamagnetic iron oxide (SPIO) immersed in different carrier fluids, and the behavior of which has been characterized experimentally under weak magnetic fields. The experimental results clearly show that the observations properly follow the model prediction. Soft magnetic microrobots with controllable shape deformation have great potential for targeted drug delivery due to the adaptability of their characteristics to environmental conditions (e.g. vessel size, velocity, shear stress).

We report an experimental study of the bimagnetic nanocomposites CoFe2/CoFe2O4. The precursor material, CoFe2O4 was prepared using the conventional stoichiometric combustion method. The nano-structured material CoFe2/CoFe2O4 was obtained by total oxygen reduction of CoFe2O4 using a thermal treatment at 350 °C in H2 atmospheres following the partial oxidation in O2 atmospheres at 380 °C during 120; 30; 15, 10, and 5 min. The X-ray diffraction, Mössbauer spectroscopy and transmission electronic microscopy images confirmed the formation of the material CoFe2/CoFe2O4. The magnetic hysteresis for the nanocomposite with different saturation magnetization (from 87 to 108 emu/g) also confirms the formation of the CoFe2/CoFe2O4 with different content of CoFe2O4. Furthermore, the magnetic hysteresis curves for all samples presented a single magnetic behavior, suggesting the magnetic coupling between the phases of the nanocomposite. The effects of high energy milling on the magnetic properties of the precursor material and nanocomposites samples were evaluated.

We report upon synthesis of stable chains of magnetically aligned zero-valent α-Fe nanoparticles and investigation of their magnetization reversal mechanism. The magnetic hysteresis loops with magnetic field applied at various directions with respect to the nanoparticle chain are measured experimentally and reproduced numerically by precisely mimicking the sample geometry under finite element modeling. The magnetization reversal mechanism is visualized in all three dimensions (3Ds) using 3D simulation and visualization toolkits. The reversal is found to nucleate from the ends of the chains and progressed through curling and fanning modes, vortex nucleation, propagation and annihilation. A better quantitative agreement is observed for increased number of nanoparticles and parallel chains.

Two Fe–Ni alloys were prepared using the arc melting method: Fe50Ni50 and Fe64Ni36. The samples after annealing were reheated up to 650°C and cooled at a very slow rate to approach thermodynamic equilibrium. The coarse grains of the as prepared samples have been substantially reduced after thermal process resulting in a larger fraction of grain boundaries and a higher diffusivity. Magnetic hysteresis curves reveal an increased coercivity of the cooling processed samples compared to the annealed samples. These results suggest that during slow rate cooling a partial phase transition of disordered γ-FeNi to ordered L10 is possible to occur.

An inter-comparison of the superconducting properties of Cu0.5Tl0.5Ba2(CaMg)Cu3O10-δ and Cu0.5Tl0.5Ba2(CaMg)Cu1.5M1.5O10-δ (M = Zn, Ni)-doped samples was undertaken. Our main objective was to determine the role of electron–phonon interactions in the mechanism of high-temperature superconductivity in these oxide superconductors. We achieved this goal indirectly by doping Zn and Ni at the Cu sites in this compound. The replacement of Cu with Zn/Ni atoms induced anharmonic oscillations due to the difference in their masses. The influence of anharmonic oscillations was enhanced due to the decreased distance between the conducting CuO2/MO2 (M = Zn, Ni) planes. A comparison of zero-field-cooled (ZFC) and field-cooled (FC) magnetic moments showed suppression in the magnitude of diamagnetism with doping of Zn and Ni atoms. We suggest that the suppression in the magnetic moments arises from the difference in the atomic mass of the doped atoms in comparison with Cu atoms. With doping of Zn and Ni, the width of the magnetic hysteresis loops and their critical current density are suppresses. These decreased values in the doped samples give rise to huge anharmonic oscillations that suppress the population of phonons necessary for the mechanism of electron–phonon interactions

We used helical antenna-coupled radio frequency (RF) plasmas to study the evolution of the mode transition power and electron kinetics under different applied magnetic fields and argon pressures. Langmuir probe and emission spectrum data indicate that the discharge mode changes from the capacitive coupling E mode to the inductive coupling H mode through a strong mixed mode (E + H). One reason for this strongly mixed ionization is the antenna structure, which increases the capacitive coupling. Furthermore, the $\text{E}\to \text{H}$ transition threshold power decreases with increasing pressure regardless of whether there is a magnetic field, and the presence of the magnetic field significantly increases the transition power. The electron energy distribution function (EEDF) curve has a Druyvesteyn shape at low RF power (E mode). The presence of a magnetic field increases the electron energy range, and the binding of the electrons by the magnetic field causes the EEDF to deviate significantly from the Maxwellian shape. As RF power increases, the EEDF tends toward the Maxwellian shape during the transition from the E mode to the H mode. The magnetic field appears to act like a drag on this process, particularly at very low pressures.

We utilize a high-pressure solid-state technique to prepare yttrium hexaboride (YB6) nanowires at very low temperatures of 200–240 °C. The obtained YB6 nanowires are single-crystals grown along [001] direction confirmed by HRTEM and SAED images. From the growth morphology at different time stages and EDS evidence, we proposed that YB6 nanowires are nucleated and grown from the submicron particle clusters. The temperature-dependent magnetization results indicate that YB6 nanostructures undergo a superconducting transition with Tc = 7.8 K, which is higher than that of reported YB6 bulk single-crystals. Furthermore, the YB6 nanostructures reveal a peak effect in superconducting state observed from the magnetic hysteresis loops, approving that YB6 belongs to a type-II superconductor. The lower and upper critical magnetic fields, Hc1 and Hc2, are determined to be 251 Oe and 1104 Oe, respectively.

BiFeO3 has been recognized as one of the most important room-temperature single-phase multiferroic materials, but it still suffers from several drawbacks especially the weak magnetoelectric coupling. In the present work, the electric-field-controlled magnetism is achieved in Bi1-xGdxFeO3 system, which involves a field-induced transition of Pna21/R3c at the morphotropic phase boundary region, and the magnetic state is switched between cycloidal state and canted antiferromagnetic state. The electric-field-controlled magnetism becomes reversible with the help of annealing, which is confirmed by magnetic hysteresis loops and the quantitative ratio of the involved phases for the as-sintered, as-poled and as-annealed samples. Compared with the systems of Bi1-xNdxFeO3 and Bi1-xSmxFeO3, it is easier to tune the symmetry from R3c to Pna21 with lower rare earth-content, and the field-induced transition is more apparent and subsequently leads to more significant electric-field-controlled magnetism in a wider composition range.

Anisotropic magnetoresistance (AMR) is generally characterized by the variation of resistance under the rotation of magnetic field. When the magnetic field is much stronger than an anisotropic field, the resistance is proportional to cos $^{2}\alpha $ , where $\alpha $ is an angle between current and the magnetic field. However, when the magnetic-field strength ( $H$ ) is comparable with the anisotropic field ( $H_{a}$ ), the angle-dependent AMR depends on the competition between $H$ and $H_{a}$ . In this article, we report our numerical calculation about angle-dependent AMR under weak magnetic field for different kinds of magnetic anisotropy energy. As to uniaxial anisotropy field, when current is parallel to the anisotropic field, the angle for the extreme resistance ( $\varphi _{e}$ ) in the angle-dependent AMR curve is fixed no matter how weak the magnetic field is. While when the easy axis deviates from current at an angle ( $\varepsilon$ ), the $\varphi _{e}$ shifts under a weak magnetic field by an angle that is relevant to $\varepsilon $ . The magnetic-field-dependent $\varphi _{e}$ can also be observed for fourfold anisotropy and the combination of uniaxial and fourfold anisotropy. This work provides a possible route for analyzing the magnetic anisotropic field via the AMR measurement.

The two-dimensional hysteresis property of the soft magnetic composite (SMC) material under circular rotational excitation was measured by the experimental platform. The first-order reversal curves and the corresponding scalar Everett functions can be numerically generated by the measured major hysteresis loops along the orthogonal easy axis and hard axis. Different from the classical model, an improved vector Preisach hysteresis model that considers the anisotropic property of the SMC materials under vector magnetic excitation was put forward by introducing two parameters w and z . The two parameters were used to identify the vector Everett functions and adjust the shape of hysteresis curves under different magnitudes of the magnetic flux density. Furthermore, an efficient hybrid algorithm that combines simulated annealing with Nelder–Mead simplex technique was proposed for the accurate extraction of optimal parameters. The simulated results based on the improved model agree well with the measured ones; thus, the effectiveness and accuracy of the proposed method were verified.

In this study, we explore the vector magnetic properties of the electrical steel sheet under dc-biased flux and rotating magnetic field of different frequencies. The corresponding iron loss and the rotational eddy current loss are discussed. An enhanced vector magnetic hysteresis model is proposed to describe the $B$ – $H$ behavior under these conditions. The accuracy of the proposed model is verified by the close agreement between the hysteresis loops calculated with the proposed model and those measured experimentally, as well as by the neglectable calculation error of the total iron loss.

This article proposes the core loss reduction of a surface-mounted permanent magnet motor with a segmented stator core. First, it is shown that the core loss of a motor is decreased by the segmentation of a stator core made of a nonoriented electrical steel sheet. The nonoriented electrical steel sheet used as the segmented stator core has an anisotropy, which is easy to magnetize in the rolling direction. Therefore, it is important to investigate the core loss of the segmented stator core in consideration of the rolling direction of the electrical steel sheet. The rolling direction of the steel sheet can be taken into consideration in magnetic field analysis by using the Enokizono & Soda (E&S) model, which is one of the vector magnetic property utilization techniques. Accordingly, the finite-element method, which introduced the E&S model, is used to evaluate the core loss of the motor. Second, the core loss of the segmented stator core is further reduced by applying a corner radius to each tooth root. Finally, the relation between the core loss and the rolling direction in the segmented stator core applying corner radius is investigated.

The Barkhausen noise is a magnetic phenomenon employed for the non-destructive evaluation of ferromagnetic samples, mainly for microstructure evaluation and detection of surface defects. Its interpretation is still qualitative because the Barkhausen noise is sensitive to a great number of parameters, like the grain size. A simulation tool, allowing testing a great number of configurations, is sorely needed to improve quantitative analysis of Barkhausen noise measurements. The chosen simulation tool is the combination of the multi-scale model (MSM), giving anhysteretic functions as outputs, with a classical hysteresis model. The hysteresis loop of the Barkhausen noise has been obtained with the MBNE loop and it has been simulated by removing the magnetization rotation contribution in the MSM. This approach allows to compare the MBNE to the classical hysteresis loop, which has been tested without and with an uniaxial mechanical stress. Measurements have found a qualitative agreement with simulated loops, a better precision requiring very detailed studies on the texture of the material. 2D simulations show that the sensitivity of MBNE magnetic indicators heavily depend on the direction of both mechanical and magnetic excitation. A feedback algorithm has been implemented to obtain the sinusoidal magnetic induction required by the Statistical Theory of Losses (STL). First results show that the relationship between MBNE surface and excitation loop is similar to the classic STL law, which could be exploited to standardize the MBNE normalization coefficient. The association between MSM and hysteresis model gives qualitative results allowing to anticipate some trends of the chosen magnetic indicators, mainly when the mechanical stress is variable.; Le bruit Barkhausen (MBN) est un phénomène magnétique utilisé pour le contrôle non destructif de pièces ferromagnétiques (évaluation de microstructure, détection de défauts surfaciques, etc.). Sa mesure reste délicate à interpréter quantitativement car il dépend d’un grand nombre de paramètres, comme la taille des grains, la densité de dislocations ou les contraintes internes. Un outil de simulation, permettant de tester un grand nombre de configurations et de faire varier les propriétés internes du matériau, est très attendu pour améliorer l’analyse du bruit Barkhausen. L’approche choisie dans cette thèse consiste à combiner un modèle multi-échelle (MME), donnant des courbes anhystérétiques, et un modèle d’hystérésis classique. Des cycles d’hystérésis associés à la mesure MBN et à son énergie (MBNE) sont mesurés et simulés en prenant soin d’annuler la contribution liée à la rotation de l’aimantation dans le MME. Un accord qualitatif a été obtenu, une précision plus poussée pouvant être atteinte grâce à une étude fine de la texture du matériau. Aussi, des comparaisons ont été réalisées entre cycles classiques sans et avec contraintes mécaniques unidirectionnelles afin de comprendre leur influence sur la cinétique des domaines magnétiques. Des simulations 2D ont montré que la sensibilité des indicateurs magnétiques pour le bruit Barkhausen est très affectée par la direction de la contrainte et de l’excitation magnétique. Finalement, un algorithme d’asservissement a été mis en place pour obtenir une densité de flux sinusoïdale et se placer dans le cadre expérimental de la théorie statistique des pertes (STL). La relation entre l’aire du cycle MBNE et la fréquence d’excitation est très similaire à la relation classique, ce qui ouvre une voie pour normaliser l’amplitude du MBNE. En conclusion, l’association entre MBNE et modèle d’hystérésis donne de résultats qualitatifs permettant d’anticiper certaines tendances des indicateurs magnétiques, notamment pour des contraintes mécaniques appliquées à une pièce.

The entropy changes of successive martensitic phase transformations in Ni-Mn-Ga Heusler alloys can be utilized to realize enhanced magnetocaloric properties. A detailed study of phase transformations of one such alloy, Ni2.15Mn0.85Ga, (ΔQ = 4900 J/kg at 343 K, under 140 kOe), is reported here. Upon cooling, the paramagnetic cubic (L21) austenitic phase transforms into a ferromagnetic 7M modulated monoclinic martensitic phase. This phase is stable in a narrow temperature range, and upon further cooling, transforms into a non-modulated ferromagnetic tetragonal (L10) phase. The separation between the equilibrium temperatures of the austenitic and tetragonal martensitic phases is only ~50 K. The alloy undergoes reversible temperature-induced martensitic and inter-martensitic phase transformations with thermal hysteresis of about 25 K. The conclusions from the detailed study of the phase transformations lead to new possibilities to enhance the magnetocaloric effect by utilizing the entropy associated with multi-structural transformations.

This work described the structural, morphological, temperature-dependent relative permittivity, and magnetic behavior of nickel ferrite (NiFe2O4) nanoparticles prepared via a facile co-precipitation method. A computational analysis, density functional theory (DFT) calculation was carried out to understand the band structure and density of the state of NiFe2O4. The crystallinity and phase purity was analyzed by powder X-ray diffraction, which confirms the polycrystalline nature of the cubic spinel structure of NiFe2O4 belonging to the Fd3m space group. The calculated crystallite size is about 22 nm. Field emission scanning electron micrograph confirms the agglomerated flake-like grains. All the phonon modes (A1g, Eg and T2g) confirm the inverse spinel cubic structure of NiFe2O4. The dielectric study shows that the relative permittivity is varied between 1.2 × 102 and 1.6 × 103 as a function of different temperature. The obtained semicircle arc from the Cole–Cole plot confirms the grain and grain boundaries contribution in the conduction process. The exploration of the magnetic hysteresis loop measured in the temperature between 5 and 300 K over the field strength of ± 2 T, revealed a ferromagnetic behavior. Temperature-dependent magnetization and coercivity were studied using modified Bloch’s law and Kneller’s law, respectively. The increasing magnetic parameters at low temperature may be due to increasing the surface-spin moment in the finite-size nanoparticles.