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Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a simple dynamic vector-play model to calculate the iron loss and describe the vector hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under 50 Hz rotating magnetic fields. Based on the iron loss separation theory, the proposed model is separated to the static hysteresis component and eddy current component. The static hysteresis component is constructed by vector play model, which is identified by using 1 Hz minor B – H loops. And two coefficients \omega x and \omega y are introduced to consider the anisotropic property of NO ESS and the excess loss of eddy-current component under 50 Hz magnetic field. The validity of the proposed dynamic vector hysteresis model is verified by comparing it with the experimental results under various 50 Hz magnetic field conditions. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent magnetic hysteresis (B–H) curve for magnetic multiscale problems of complex materials composed of electrical conductors separated by insulating material. The conventional method, which assigns equivalent material constants to each material, cannot properly express the local eddy current loss and the extra magnetic field derived from the local eddy current. To solve this problem, we derive the magnetic hysteresis curve from the volume-averaged magnetic flux density and the surface magnetic field in the micro-model, and apply this curve to the macro-model. The mesh number of the novel macro-model is reduced to around one-tenth that of the micro-model. Magnetic hysteresis is treated by a free energy magnetic hysteresis model, and the macro-model ignores electrical conductivity. The magnetic hysteresis curve and the numerically calculated losses are consistent in the micro- and macro-models. The proposed method well expresses the local eddy current phenomena. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling of vector fields that exhibit hysteresis. A general class of models of vector magnetizations with hysteresis that form a natural extension of the Classical Scalar Preisach Model is defined. Although the modeling was done for the 2-d case, the same theory can be extended to the 3-d case as well. After reviewing some general properties of conservative fields, the specific case of unit magnitude vector fields is discussed. The paper focuses on discussing the properties of a general vector hysteresis operator (hysteron). The mathematical approach followed here can be applied not only to the magnetic hysteresis, but also to any hysteresis process. Some examples of vector hysterons, deduced from the general definition, are presented and their properties analyzed. [ABSTRACT FROM PUBLISHER]

This paper deals with the mathematical definition of a general vector hysteresis operator in 3-D, as an extension of previous papers where the theory has been limited to the 2-D case. Although the paper is mainly focused on magnetic hysteresis, the definitions and the results reported can be applied to any general physical phenomenon that exhibits hysteresis. We show here the main general properties of the general hysteresis operator in 3-D. [ABSTRACT FROM AUTHOR]

This paper compares two different identification methods of a static rate-independent energy-based hysteresis model with regard to the dynamic hysteresis loop shape prediction when coupled to the parametric magnetodynamic lamination model. The values of hysteresis model parameters are determined solely based on the quasi-static major loop. A semiphysical approach identifying the reversible and irreversible field components independently and a purely mathematical scheme using a differential evolution optimization algorithm determining all parameters simultaneously are compared. Both variants of parameter identification are analyzed in terms of hysteresis loop shape prediction for quasi-static as well as dynamic loops. [ABSTRACT FROM AUTHOR]

The knee point in the B – H curve of a permanent magnet (PM) is considered crucial in electric motor applications. In the case of severe fault conditions, such as overheating or a short circuit in electric motors, the working point might fall below the knee point causing irreversible demagnetization of the PM. Hence, the remanence flux decreases and the motor operation would be reduced or stalled. In this paper, two demagnetization models of PMs are investigated, i.e., a linear model and an exponential model. Demagnetization curves for NdFeB were measured at temperatures varying from room temperature to 180 °C. It was found that all the parameters in the exponential model, including Br , H\mathrm {jc} , \mu r , and the fitting parameter K1 , are temperature dependent. Therefore, an exponential model can be developed as a function of temperature which allows a more efficient implementation within electric motor applications using PMs. However, comparison of the exponential and linear models indicates that the latter has a better accuracy near the knee point for the demagnetization curves of NdFeB magnets. [ABSTRACT FROM AUTHOR]

This paper discusses the implementation of the inverse Jiles–Atherton vector hysteresis model with the 2-D Finite Element Method (FEM) for the analysis of an induction machine operating as self-excited generator. A differential reluctivity tensor couples the hysteresis model with the magnetic vector potential-based finite-element model. Experimental and simulated results (transient and steady state) are presented. [ABSTRACT FROM AUTHOR]

Some soft magnetic materials are strongly dependent on the temperature, because of their low Curie temperature. In order to predict their behavior in electrical devices, engineers need hysteresis models able to consider the temperature. This paper is an attempt to consider the temperature in an existing model of static hysteresis through its parameters. Variations of some parameters with temperature are issued or build thanks to the literature. At the end, all needed parameters have an analytical law versus temperature. The simulation results are compared with measurements and discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a sensor for leakage-current detection based on the magnetic modulation technology. The sensor can measure both nonlinear current with an arbitrary waveform and linear current from dc to several kilohertz. The current sensor consists of only one magnetic core and one winding, which significantly reduces the sensor size. The structure and operating principle of the current sensor are introduced, and the dynamic process of the current sensor is analyzed. In addition, the mathematical model of dynamic process with hysteresis considered for the current sensor is presented. Both the simulation and the experimental results are presented to verify the effectiveness of proposed current sensor. [ABSTRACT FROM AUTHOR]

Recent advances have been made into modeling the soft-magnetic materials using the surface charge model. Until now, the model has only been used to model the field outside the soft-magnetic material. To include the saturation in the future, the magnetic field inside the material should be known. In this paper, the model is used to calculate the field inside the material when three different shapes of boundaries are considered. Comparing the results with Finite Element Method shows that the differences in the air region are <1 mT and those in the soft-magnetic region are <4 mT. Larger discrepancies can, however, occur near the corner of the material. [ABSTRACT FROM AUTHOR]

The grain flipping probability (GFP) model is used to reproduce the output of micromagnetic ( $\mu $ -mag) simulations several orders of magnitude faster. In this paper, we compare signals from the $\mu $ -magsimulations and the GFP model with readback from a Seagate hard disk drive (HDD). We validate our models by benchmarking the model output against the HDD readback in terms of magnetic write width, and signal-to-noise ratio and bit error rate as a function of the overshoot triplet parameters. [ABSTRACT FROM AUTHOR]

This paper shows that a Preisach engine, based on the classical Preisach model of hysteresis and identified using the Everett integrals and the first-order reversal curves, can be used whatever the orientation of the hysteresis loop [counterclockwise or clockwise] and whatever the monotonicity of the branches (increasing/decreasing). This is important for the use of the Preisach model in many innovative applications, such as hysteresis compensators in magnetostrictive devices and lithium-iron-phosphate rechargeable battery, as both the applications are characterized by clockwise hysteresis loops and strictly increasing loop branches. Numerical simulations of both cases, compared with experimental data, prove the validity of the approach. [ABSTRACT FROM AUTHOR]

This paper proposed a temperature-dependent iron loss model and corresponding dynamic hysteresis model, where temperature coefficient k is introduced to consider the thermal effect on eddy-current loss. The iron loss model is validated by massive experimental measurement of test samples, 1174 combinations of various temperatures, magnetic inductions, and frequencies for nonoriented silicon steel specimen. The relative error of the model is $\sim 11$ % in a wide range of 50–400 Hz, 26 °C–200 °C, and 0–2 T. The proposed method can be applicable to other types of magnetic materials as long as whose resistivity rate exhibits approximately linear thermal dependence within a temperature range of 26 °C–200 °C. [ABSTRACT FROM AUTHOR]

This paper describes a mathematical model for the dynamic magnetic power losses in the laminated steel stator of high-frequency permanent magnet machines, such as brushless dc (BLDC) motors. The model presented is based on a utilization of the dynamic Jiles–Atherton model. Accurate dynamic $B$ – $H$ curve fitting and magnetic power loss derivations have been achieved, where the calculated magnetic losses have shown $\sim 95$ % accuracy from 5 to 2000 Hz over a flux density range of 1.0–1.6 T. This approach has been applied to estimate the magnetic power loss of a small scale high-frequency (>10 000 r/min) BLDC motor, with calculated and measured losses being in close agreement. [ABSTRACT FROM AUTHOR]

Hysteresis models can incorporate the effects of operating conditions (frequency, stress, and temperature) on iron losses incurred in ferromagnetic materials. Among such models, the Jiles–Atherton (JA) and Preisach models are the most popular and various modifications of these have been proposed in the literature to model the effect of frequency, stress, and temperature on iron losses. Both of these representations produce accurate results compared with the curve fitting models and can be directly implemented in finite element simulations. Unfortunately, it is very difficult to incorporate all these effects into a single iron loss model that is computationally efficient and can predict iron losses with reasonable accuracy for a given range of these parameters. In this paper, an effort has been made to establish a relationship between JA and Preisach models and an interpolation-based approach is presented to predict iron losses that utilizes the Preisach model on top of the JA model and incorporates all of the above factors. It is shown that iron loss can be predicted accurately for any value of frequency, stress, and temperature. [ABSTRACT FROM PUBLISHER]

To develop efficient silicon steel plates and electric machines using silicon steel laminations, the evaluation of excess loss in silicon steel plates is important. In this paper, investigation on excess loss calculation using the finite element method is carried out. The excess loss, which is mainly due to two factors, lack of flux penetration and domain wall pinning, is considered by the proposed approach using the domain wall bowing degree (DWBD), which depends on the above two factors. The DWBD is obtained using nonlinear eddy-current analysis. The correlation between the excess loss and the DWBD can be expressed as an exponential equation. Using the equation, the excess loss can be predicted under harmonic frequency in the range of 50–2000 Hz. These results can be applied to iron loss estimation, especially, when there are harmonics in the power supply. [ABSTRACT FROM PUBLISHER]

Electric motors fabricated with aluminum–nickel–cobalt (AlNiCo) permanent magnets (PMs) can be operated over a wide speed range, as the strong nonlinear demagnetization characteristics of AlNiCo allow effective and efficient airgap flux control. This paper presents a linear hysteresis model which is derived from the Preisach model for AlNiCo PMs, to be incorporated into the time-stepping finite element method to study the motor performance, especially transient performance, accurately and effectively. The proposed method can significantly reduce the computing time without scarifying the accuracy of the Preisach model. The validity and accuracy of the proposed method are verified by both simulation and experimentation. [ABSTRACT FROM PUBLISHER]

This paper presents a vector hysteresis model based on micromagnetic theory. In this model, a magnetization state of a magnetic material is described by a collection of single-domain particles, and magnetic reversal processes due to domain-wall motions are treated approximately as a magnetization flip. The present model is applied to calculation of hysteresis properties of grain-oriented silicon steel. The simulation results show that the anisotropic hysteresis properties and iron loss can be reproduced accurately by the present model. [ABSTRACT FROM AUTHOR]

The magnetic tunnel junction (MTJ) effect has been widely applied in information technology and has brought about many revolutionary products in the past decade. In the meantime, many research studies on linear magnetoresistive sensors based on MTJ have been published to improve their performance metrics, such as linear field range, sensitivity, hysteresis, and noise. Though the frequency response of high-speed magnetic reading has been researched, the performance and application of linear magnetoresistive sensors with bridge configuration for high-frequency sensing remain underexplored. In this paper, we proposed an equivalent impedance network model of packaged linear magnetoresistive sensors based on MTJ with Wheatstone bridge configuration, and derived the corresponding frequency-dependent performance model, considering the influences of the parasitic capacitances and the amplitude of the applied magnetic field. Our work shows that the frequency characteristics of linear magnetoresistive sensors are closely associated with their $RC$ time constants, which depends on their resistances and parasitic capacitances. The useful bandwidth of an MTJ linear sensor is also related to the amplitude of the applied magnetic field. The bandwidth changes negligibly with the varying magnetic field in the range of less than 30% of the saturation field, but increases rapidly when it exceeds 30% of the saturation field. [ABSTRACT FROM AUTHOR]

In this paper, we present a 3-D numerical model of an integral formulation for the efficient computation of 3-D magnetic fields in hysteretic media with (time) periodic sources. The hysteretic medium is described by an isotropic vector generalization of the classical scalar Jiles–Atherton model. The nonlinear algebraic system is solved using Picard–Banach iterations in the frequency domain. The full matrices arising after the discretization of the main (linear) operators are suitably compressed and distributed among the nodes of a parallel computer system. The numerical model is applied for the nondestructive micromagnetic characterization (of mechanical properties) in metallic materials. In particular, the problem of estimating incremental permeability is analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we present a benchmark problem for the validation of numerical models of vector magnetic hysteresis. The problem geometry and the measurement system are described. The materials considered are both oriented grain (OG) and not OG Si-Fe steels. A series of experimental data about magnetic field and magnetic induction loci under rotational magnetization are presented with the corresponding magnetic losses. The measured data can be useful as a reference for the numerical models testing, comparison, and development. In addition, we propose here a comparison of the experimental data with the numerical results computed using a vector hysteresis model based on the extension of the Preisach model in 2-D. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the numerical modeling of hysteresis in magnetic steels with oriented and nonoriented grain. The modeling is fully 3-D, but it is applied here to typical 2-D magnetic problems. Starting from a vector generalization of the Preisach model, we introduce here the concept of an operative magnetic field, function of the state of magnetization of the material. This operative field is introduced to reproduce with more accuracy the peculiar behavior of Si-Fe steels approaching the saturation state. The properties of the model are discussed and some examples are reported. [ABSTRACT FROM AUTHOR]

The performance prediction of micro-generators based on the Villari effect is a task which involved engineers and physicists in the last years. A number of approaches have been proposed, ranging from the linear one to those including non-linearity and hysteresis, up to phenomenological approaches. The present work particularly focuses on a hysteretic approach derived from a model successfully experimented for the analysis of magneto-mechanical actuators and based on the implementation of stress-dependent hysteretic model within a finite element procedure. The paper presents the validation of the proposed approach, and its effectiveness in the characterization of the generator. [ABSTRACT FROM PUBLISHER]

This paper describes the magnetic field analysis of a ring core taking account of hysteretic properties of magnetic materials by the play model. The numerical results are compared with the measured results to demonstrate the effectiveness of the play model and some features of the play model due to its rate-independent properties are discussed. Furthermore, the novel time-periodic explicit error correction method suitable for the magnetic field analysis taking account of the hysteretic property by the play model is proposed for the improvement of the convergence to the steady state in the time-periodic transient analysis. [ABSTRACT FROM PUBLISHER]

In this work we present a physical-related model of vector hysteresis for magnetic simulation of nanometric structures. The mathematical formulation, based on a generalization of the Preisach and Stoner-Wohlfarth models, is very simple and elegant. The numerical implementation is very easy and the computation time required for the simulations is extremely fast. However the accuracy is not comparable with the codes based on the micromagnetic theory, but it is sufficient for the use as preprocessing of more accurate and more complex methods, in order to speed up the convergence. In this paper the model identification is performed for a nanoscale spin valve using the data generated by a 3D micromagnetic code. [ABSTRACT FROM AUTHOR]

Environmental requirements currently placed on magnetic materials that are used in both domestic and professional electromagnetic devices are becoming more stringent. The growing demand for components to operate under extreme environmental conditions prompted this study of the effect of temperature variation on magnetic materials. Thus, the knowledge of their behavior, especially under high temperatures, is of prime importance. In this paper, two methods for determining the evolution of Jiles-Atherton model parameters with temperature are presented. The parameters evolution of the model as a function of temperature is discussed. Both methods are compared. [ABSTRACT FROM PUBLISHER]

This paper focuses on the thermal stress on magnetic materials under Curie temperature. The influence of the temperature on static and dynamic major B(H) loops is studied. Then, the Jiles-Atherton (JA) model and “flux tube” model are used, in order to reproduce the static and dynamic hysteresis loops for a NiFe (80/20) alloy. For each temperature, the six model parameters are optimized from measurements. Finally, these parameters are used in order to reproduce the behavior of a current transformer. The simulation results are compared with measurements and discussed. [ABSTRACT FROM PUBLISHER]

The permanent magnet (PM) is the key part of the relay. This paper aims to solve the problem of the uneven magnetization for the PM with nonlinear demagnetization curve after magnetizing and demagnetizing. A method partitioning the PM along the magnetization direction and the vertical direction of magnetization according to the condition of the specific magnetization of the PM was presented. By this method, the demagnetization model of the PM was built, the state of the PM magnetization was simulated under the demagnetizing magnetic intensity, and the recoil line and its initial point of each partition of the PM were obtained. Then the characteristic of the recoil line of each partition was used as its magnetic characteristic for the equivalent model of the PM to calculate the static torque characteristics under the demagnetizing magnetic field. Finally, the static torque characteristics of simulation and experiment were compared and the validity of the equivalent model presented was verified. [ABSTRACT FROM PUBLISHER]

This paper presents the result of modeling the magnetic characteristics of ring-shaped cores made of Fe41.5Co41.5Nb3Cu1B13 alloy in both as-quenched and nanocrystalline state. For the modeling, the extended Jiles–Atherton model was used. Extension of Jiles–Atherton model is focused on taking into account the changes of parameter k caused by changes of the average energy required to break pinning site. Determination of model's parameters was made on the base of optimization process. This optimization covered both evolutionary strategies and simulated annealing. Finally, good agreement between experimental characteristics and the results of modeling was achieved. This agreement is confirmed by the high value of R^2 determination coefficient, which exceeds 99% for both as-quenched and annealed cores. As a result, it was confirmed that the presented method of modeling the magnetic characteristics of Fe41.5Co41.5Nb3Cu1B13 alloy in both as-quenched and nanocrystalline state is suitable for technical applications. [ABSTRACT FROM PUBLISHER]

In this paper, the identification of soft magnetic B-H characteristics when using the single measured hysteresis loop and fitting the discrete dynamic Preisach (DDP) model is addressed. The magnetic measurements with primary and secondary windings are performed to obtain the magnetostatic system response. The constrained least-squares estimation of the Preisach density function yields the global solution even for limited hysteresis data. The uncertainties detected during the measurement and computation of B and H values are discussed. [ABSTRACT FROM PUBLISHER]

The paper proposes an improved analytical model, valid for a wide frequency range, of interlaminar short-circuits on the edges of the sheets of high power transformers working at 50–60 Hz. This model is able to determine the current flowing in the microscopic interlaminar contacts formed by burrs, in order to estimate the maximum power dissipated in such hot spots. With this theoretical approach, it is also possible to get an interpretation of impedance measurements on a test coil wound around the core, in order to define a new index able to characterize the part of the shearing burrs in the manufacturing factor of large transformer cores. This new index will help the transformer manufacturers to improve their processes. [ABSTRACT FROM PUBLISHER]

This paper presents a method for calculating eddy current loss based on reluctance network analysis (RNA) considering the magnetic reaction field caused by the eddy current. First, an electric network model for calculating eddy current is indicated. Next, RNA model considering the magnetic reaction field by using magnetic inductance is presented. The validity of the proposed model is proved by comparing with the finite-element analysis and experiment. [ABSTRACT FROM AUTHOR]

This paper describes an approach to an electromagnetic harvester exploiting the magnetostrictive properties of amorphous ribbons to generate an electromotive force upon time-varying stresses of vibrational origin. Alloys of composition Fe78B13Si9, thermally treated for maximum magnetic response to tensile stresses, are considered. A compact design is proposed, where the sensing core, a short bundle of few flux-closed amorphous strips subjected to a bias dc field, is connected at one end to a vibrating wall. A finite element calculation of the whole device under different resistive load conditions on the secondary circuit is made. It results into a power around 20 \muW/cm^3 per unit volume of core material delivered into the load at 100 Hz. [ABSTRACT FROM AUTHOR]

This paper introduces the idea of degaussing of perpendicular magnetic recording (PMR) heads, the approach generally accepted by the magnetic recording industry. Basic theoretical aspects of degaussing are discussed. A simplified approach based on write current turnoff is first studied. Second, an advanced degaussing method involving a sequence of write pulses of opposite polarities and decaying amplitude is analyzed using micromagnetic modeling tools. Dependences on degauss waveform parameters like frequency and duration are studied to provide guidance to find optimal solutions for reliable writer degaussing. [ABSTRACT FROM AUTHOR]

This paper presents a new flux-mnemonic dual-magnet brushless machine which incorporates both the neodymium-iron-boron (NdFeB) and aluminum-nickel-cobalt (AlNiCo) permanent magnets (PMs) for hybrid excitation. By applying a temporary current pulse in a small magnetizing winding to online tune the magnetization of AlNiCo PMs, the proposed machine can provide flexible air-gap flux control, thus achieving high efficiency at different speeds and loads. By newly using a parallelogram to model the AlNiCo PM hysteresis loop and then incorporating into the finite element field equation, the performance of the proposed machine is analyzed. Finally, experimental results are given to verify the simulation, confirming the validity of the proposed machine and its analysis. [ABSTRACT FROM AUTHOR]

In this paper, a synthesis of design methodologies for electromagnetic devices made with soft magnetic composite (SMC) material is presented. To realize efficient and low-cost SMC devices, it is necessary to benefit from interesting isotropic SMC material properties such as 3-D flux circulation path. In this case, the best approach is to carry out a topological structure research and perform a global optimization using physical models. However, the iterative optimization process can be computationally intensive and some compromises should be found between accuracy and computation time. One way is to use coarse models with important simplifying hypotheses but the optimal solution is often not valid. In this case, one can perform a limited number of finite element (FE) simulations to compute some correction coefficients and improve optimization convergence to a valid optimal solution. Another way is to perform the device optimization by using directly FE models with low mesh density and several simplifications of the device geometry. Such design approaches are illustrated by three concrete realizations with SMC material. [ABSTRACT FROM AUTHOR]

Magnetic gears are able to transmit torque without mechanical contact. Therefore, these have attractive features, such as low acoustic noise and maintenance-free operation in comparison with conventional mechanical gears. Planetary-type magnetic gears, especially, have higher transmission torque than the other types, and are expected to be put into practical use. This paper presents a method for calculating dynamic characteristics of the magnetic gear based on reluctance network analysis (RNA). The RNA has several features, including a simple analytical model, high calculation accuracy, and ease of coupled analysis with rotational motion of rotors. [ABSTRACT FROM AUTHOR]

In this paper, the effect of a symmetric distribution of dipolar fields acting along the applied field on the magnetization curve of a superparamagnetic nano-granuler system is examined. The calculations show that the magnetization curves are depressed when the spread of dipolar fields is increased. This reduction in magnetization is attributed to the nonlinear response of magnetization which weighs negative dipolar fields more strongly than the positive dipolar fields. Thus, the reduction in magnetization is not indicative of a predominant negative interaction field, since positive and negative fields are equally probable. Also, for the system examined, the nonlinear response of magnetization is responsible for the predicted negative average ordering temperature in the temperature variation of the initial susceptibility. Thus, in random systems, the interpretation of a negative ordering temperature as antiferromagnetic order, or the positive ordering temperature as a ferromagnetic order should be cautiously stated. [ABSTRACT FROM AUTHOR]

This paper deals with key problems that have been commonly encountered in the implementation of the Preisach model into finite-element (FE) programs. Such problems include the inverse problem imposed by certain FE formulations, the abundance use of experimental data needed for identification, and the complex hysteretic nonlinearity inherited in electromagnetic problems. The aim is to alleviate these problems using new efficient algorithms to facilitate the inclusion of the Preisach model in FE equations. The inversion of the model is evaded by systematically creating an inverted Everett function identified from a few parameters usually provided by the makers of electrical steel. The Everett function and its derivatives are ensured to be smooth and continuous by using cubic spline interpolation, which is important for producing stable iterative solutions in the FE computations. Thorough investigations and FE simulations supported by experiments show that the proposed algorithms are capable of successfully accomplishing good accuracy, fast computation, and numerical convergence. [ABSTRACT FROM AUTHOR]

In this paper, we present a set of systematic experimental investigations on possible noise mechanisms for current perpendicular thin film media of small grain sizes. In particular, we focus on intergranular exchange coupling and grain boundary surface anisotropy in the granular layer of the present continuous-granular-composite film structure. Micromagnetic modeling studies are conducted to study the impact of the observed experimental phenomenon. Modeled experiments show that significant intergranular exchange coupling may occur when oxide grain boundary thickness becomes less than 1 nm. If the grain boundary thickness has significant distribution below this critical value, the exponential dependence of the coupling strength on the oxide thickness would yield significant degradation of the medium signal-to-noise ratio. Carefully designed experiments have also been conducted to study possible grain boundary interfacial anisotropy. Co/Cr, CoPt/Cr, Co/SiO2, Co/Cr2 O3, and Co/TiO2 interfaces are investigated and the corresponding interfacial anisotropy strengths are quantitatively measured. Although Co/SiO2 interfacial anisotropy appears to be the weakest among them, the measured interfacial anisotropy energy strengths for all of them are significant fractions of the crystalline perpendicular anisotropy of the grains at present grain sizes. Finally, we investigated the impact of stacking faults in hcp Co-alloy grains. It is found that when the anisotropy strength of a small segment of a grain substantially reduces due to the existence of stacking faults, it will yield a switching field reduction disproportional to the volume ratio of the segment. [ABSTRACT FROM AUTHOR]

Hysteresis effects hinder the accurate control of electromagnetic actuators and require auxiliary sensors for properly determining the hysteretic system state. The physics-based Jiles–Atherton and the phenomenological Preisach hysteresis models provide powerful means to describe the magnetic hysteresis and its inverse. In this paper, we consider both hysteresis models in the scalar form from the control points of view, with a primary objective of the sensorless inverse feed-forward control. The identification complexity, the runtime, and the space efficiency of the control-oriented implementation are analyzed and compared for both modeling approaches. Their control performance for an inverse hysteresis compensation is experimentally evaluated on a specific force-controlled electromagnet system. [ABSTRACT FROM AUTHOR]

This paper investigates the interdependence of hysteresis and eddy-current losses in magnetic cores. Based on the results of a numerical model developed for the analysis, the magnetodynamic loss phenomena are found to be distinctly interdependent. Because of the effects of eddy currents on the flux distribution in the lamination depth, hysteresis and excess losses show a dependence on eddy currents, and hence, on the excitation frequency. Eddy-current and excess losses, on the other hand, are affected by the magnetic characteristics of the material where hysteresis plays the role of a damper. An application of the model to a rotating electrical machine has showed that the interdependence between the losses is quite significant. [ABSTRACT FROM AUTHOR]

This paper shows that two apparently independent models of hysteresis-the Jiles-Atherton model, developed by Jiles and Atherton, and the energetic model, developed by Hauser-are mathematically equivalent. These two hysteresis models are examined with respect to their capability to describe the dependence of the magnetization on magnetic field and mechanical stress. Comparisons have been made between the predictions of the two models and measured hysteresis curves. Through a mathematical analysis of the structure of the models, conditions have been found under which both models predict the same magnetization curves. This "common ground" agreement between the models has allowed us to establish correspondence between the descriptors of the models so that a mathematical transformation between the model parameters becomes possible. The result allows improved interpretation of the physical mechanisms that contribute to ferromagnetic hysteresis at different stages in the magnetization curve in terms of the reversible and irreversible physical processes such as domain wall motion and domain rotation which form the basis of these models. Furthermore, consideration of the internal demagnetizing factor has also allowed it to be included in the models. [ABSTRACT FROM PUBLISHER]

This paper describes a mathematical model enabling the calculation of the effective permeability tensor of heterogeneous magnetic materials set in various magnetization states. The theoretical approach we propose permits to predict the microwave behavior of unsaturated magnetic loaded composites as well as those of unsaturated polycrystalline ferrites. The model gives all the complex components of the permeability tensor in a single calculation phase whatever the magnetization state of the material is. This is useful for the computer-aided design of microwave magnetic devices. The calculation of the effective permeability tensor is carded out from a limited number of parameters: saturation magnetization, anisotropy field, damping factor, external dc field strength, concentration, and shape of the magnetic particles or domains. The model is predictive in the way that the magnetization state of the material is determined from the strength of the external dc magnetic field applied on the material. [ABSTRACT FROM AUTHOR]

The paper presents a method for the estimation of the iron losses under PWM (Pulse Width Modulation) flux supply conditions. The computational results are validated versus measurements on Epstein's yoke. The proposed model is based on Finite Element method formulated in the harmonic domain and takes into account ferromagnetic hysteresis and eddy currents. A classical Preisach model is used for hysteresis modelling neglecting the effects of excess losses in field analysis. Different PWM supply conditions are measured and simulated with satisfactory agreement. [ABSTRACT FROM PUBLISHER]