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The special hysteresis characteristics of a laminated core (LC) under AC-DC Hybrid magnetization are obtained by test. The field-circuit coupled time-periodic finite-element method (TPFEM) combined with the fixed-point method is used to calculate the exciting current and magnetic field of the LC based on the DC-biased magnetizing curve. The behavior of LC with no-load and different loads under AC-DC Hybrid magnetization is analyzed based on the TPFEM.

SUMMARY The remote determination of magnetic remanence in rocks is a method that has largely been ignored because of the ambiguity associated with the estimation of both the Koenigsberger ratio and remanent magnetization direction. Our research shows that the resultant magnetization direction can be derived directly through inversion of magnetic data for an isolated magnetic anomaly. The resultant magnetization direction is a property of the target magnetic rocks and a robust inversion parameter. The departure angle of the resultant magnetization vector from that of the inducing magnetic field is an important indicator of the existence of remanent magnetization and the inversion process can detect departures that are not easily detected by visual inspection. This departure angle is called the Apparent Resultant Rotation Angle or ARRA. The induced field vector, remanent magnetization vector and resultant magnetization vector lie on a great circle. We find the intersection of the polar wander vector trace with the great circle to obtain one or more possible solutions for the remanent magnetization direction. Geological deduction will normally allow us to reduce the ambiguity for multiple solutions to obtain the most likely remanent magnetization direction. Once the remanent magnetization direction is established, it is then possible to determine the Koenigsberger ratio and magnetic susceptibility for the target. We illustrate the methodology with some synthetic models and targets from Australian magnetic surveys. Magnetic remanence is a physical property of the rock that is distinct from susceptibility and this methodology provides a new tool to help with the categorization and prioritization of exploration targets.

Isolated magnetic nanowires have been studied extensively and the magnetization reversal mechanism is well understood in these systems. But when these nanowires are joined together in different architectures, they behave differently and can give novel properties. Using this approach, one can engineer the network architectures to get artificial anisotropy. Here, we report six-fold anisotropy by joining the magnetic nanowires into hexagonal network. For this study, we also benchmark the widely used micromagnetic packages: OOMMF, Nmag, and LLG-simulator. Further, we propose a local hysteresis method by post processing the spatial magnetization information. With this approach we obtained the hysteresis of nanowires to understand the six-fold anisotropy and the reversal mechanism within the hexagonal networks.

The calculation of hysteresis curves with the Stoner-Wohlfarth model is somewhat laborious. For the Nd2Fe14B phase, the second order magnetocrystalline anisotropy (K2) constant is relevant, and this case only has been discussed in some studies. In this article, a simple algorithm for the calculation of the Stoner-Wohlfarth model for isotropic NdFeB magnets is described. This algorithm makes easier the modeling of the hysteresis curves of bonded melt-spun NdFeB magnets.

In the present study, the effects of B2O3 addition on the remanence properties of barium ferrite magnets are examined. The relationship between isothermal magnetization remanence M-R(H) and demagnetization remanence M-D(H) for non-interacting single domain particles, M-D(H)=M-R(H-max)-2M(R)(H), was used in order to investigate the interactions between particles. We have found that remanence magnetization M-R increased by 40% in magnitude with B2O3 addition in addition to the weakened couplings between particles. The B2O3 addition seems to supply the required conditions for usage of these materials in the magnetic recording media. (C) 2012 Elsevier B.V. All rights reserved.

SUMMARY Rock magnetic analyses were performed on basaltic-andesitic dyke samples from the Lhasa Block, which were previously used for palaeomagnetic investigations of the India–Asia collision. The aim of the study is to prove whether antipodal directions separated in these samples represent different polarities of the Earth’s magnetic field or a self-reversal magnetization. Reflected light microscopy, domain pattern observations and energy dispersive X-ray analyses revealed two generations of titanomagnetite (TM) grains, one consisting of largesized (∼20 µm to more than 100 µm) and inhomogeneous Ti-poor TM, and another with small (smaller than ∼10 µm) and rather homogeneous Ti-rich TM grains. Partial thermoremant magnetization experiments and reflected light microscopy show that magnetostatic or superexchange interaction between these two phases is unlikely. Temperature dependence of saturation magnetization and low-temperature curves of isothermal remanent magnetization disprove a possible N-type behaviour of the samples. A self-reversal due to ionic reordering can be ruled out as it requires a high degree of oxidation of the Ti-rich TMs, which was not observed. In summary, a self-reversal magnetization is very unlikely in the studied dyke samples, and therefore the observed antipodal directions most probably represent a record of different polarity epochs of the Earth’s magnetic field. This conclusion implies that the time of remanence acquisition in the studied dykes was sufficiently long to average out paleosecular variation, supporting the significance and reliability of the palaeomagnetic results.

Magnetic hysteresis curves were calculated using the Monte Carlo method to study the dependence of magnetic properties on the distribution of local magnetic sites on the grain boundaries of sensitized Alloy 600. The simulated curves illustrate that the total number of the magnetic sites and the standard deviation of the site distribution on grain boundary influence strongly the magnetic remanence and coercivity. The magnetic system can, therefore, be regarded as a magnetic granular structure with a distribution, and the results suggest a possibility of new method to control magnetic hysteresis.

Methods of higher harmonics applied to study the effects associated with the induced magnetic anisotropy (IMA) of ferro- and ferrimagnetic materials are considered. Physical processes causing the anisotropy and small value of these effects are analyzed. It is demonstrated that the IMA can remember the pressure at which it was formed.

Magnetic coercivity (HC) and remanence (MR) of Fe/Au (111) multilayered structures (MLS) containing subnanometer-thick Fe sublayers prepared by dc sputtering method were investigated both experimentally and theoretically as a function of temperature. Magnetization processes were measured using the magneto-optical technique in polar and longitudinal Kerr geometry within the temperature range 8–315 K. The experimental results are very well explained by the theoretical model developed for a system of particles with size distribution, in which the magnetic interparticle interactions in the mean-field approach and temperature dependent anisotropy of the particles were included. It is shown that the key factor for the correct theoretical description of effective HC(T) and MR(T) for the system of particles is that the coercivities and remanences of individual particles should be treated on an equal footing in the integration with the distribution function. For the systems studied, the dominant contribution to the effective magnetic anisotropy comes from the shape anisotropy. The results obtained for Fe/Au MLS show that modeling of the system coercivity only is not sufficient, and modeling of the magnetic remanence is equally important. The model can be applied to other complex systems of interacting particles with size distribution.

We study the magnetic in-plane anisotropic fields for a two-dimensional film by including magnetic field in the basal plane for an easy axis film. We present the balance between the applied field and in-plane anisotropic field at equilibrium. We have also investigated the approach to saturation of magnetization and numerically solving the nonlinear equation for equilibrium, and results are discussed in connection with experimental data reported for Co films.

The influence of thickness on magnetic interaction and magnetic properties in electrodeposited CoPt magnetic films was investigated from the analysis of the magnetic remanence curves and the magnetic hysteresis loops. As the thickness of the CoPt film is increased, the perpendicular coercivity and the saturation magnetization are increased but the squareness is considerably decreased. The analysis results of the magnetic remanence curves and the magnetic hysteresis loops exhibited that the dipolar interaction is the main interaction mechanism for all samples, but the strength of the dipolar interaction gradually increased with increasing sample thickness.

A theoretical investigation of the effect of mechanical stresses on the remanent magnetization has been performed in terms of the model of single-domain noninteracting nanoparticles. Relationships have been obtained which define two main types of remanence in the entire range of stresses. In the low-field approximation, the magnetization of the first type, whose mechanism of formation is similar to that of the normal remanence, is quadratic in both the magnetic field and stresses and only slightly changes with increasing stresses. Depending on the relationship between the magnetostriction constants, this magnetization can both increase and decrease with increasing stresses. The magnetization of the second type, which arises as a result of a nonmonotonic behavior of the critical fields of nanoparticles depending on mechanical stresses, is proportional to the magnetic field and mechanical stresses. It has been shown that the longitudinal remanence arising in the field of stresses parallel to the magnetic field is always greater than the transverse remanence. The behavior of the remanence with increasing mechanical stresses depends substantially on whether this magnetization is formed in a loaded state or in a state unloaded after plastic deformation. In the range of deformations where the anisotropy of the applied stresses is less than the magnetocrystalline anisotropy, the plastic tension should lead to a decrease in the magnetization as compared to that arising in the plastically undeformed state. Plastic compression can lead to both an increase and a decrease in the remanence.

In this paper, we present an application of the so-called hyperbolic model of magnetization. The model was modified and it was applied for nine different soft magnetic alloys. The tested samples were electro-technical steels (FeSi alloys) and a permalloy (FeNi alloy) with strongly different magnetic properties. Among them, there are top, medium and definitely poor quality soft magnetic materials as well. Their minor hysteresis loops and normal magnetization curves were measured by alternating current measurement. The hyperbolic model of magnetization was applied for the experimental normal magnetization curves. It was proved that the applied model is excellent for describing mathematically the experimental magnetization curves.

The scaling law of minor loops was studied on an amorphous alloy Co66Fe3Cr3Si15B13 with a very high initial permeability (more than 150000) and low coercivity (about 0.1 A/m). An analytical expression for the coercive force in the Rayleigh region was derived. The coercive force is connected with the maximal magnetic field Hmax via the reversibility coefficient μi/ηHmax. Reversibility coefficient shows the relationship between reversible and irreversible magnetization processes. A universal dependence of magnetic losses for hysteresis Wh on the remanence Br with a power factor of 1.35 is confirmed for a wide range of magnetic fields strengths.

Angular dependent magnetization reversal has been investigated in Co2MnAl (CMA) full Heusler alloy thin films grown on Si(100) at different growth temperatures (Ts) by DC-magnetron sputtering. An M-shaped curve is observed in the in-plane angular (0°–360°) dependent coercivity (ADC) by magneto-optical Kerr effect measurements. The dependence of the magnetization reversal on Ts is investigated in detail to bring out the structure-property correlation with regards to ADC in these polycrystalline CMA thin films. This magnetization reversal ( M-shaped ADC behavior) is well described by the two-phase model, which is a combination of Kondorsky (domain wall motion) and Stoner Wohlfarth (coherent rotation) models. In this model, magnetization reversal starts with depinning of domain walls, with their gradual displacement explained by the Kondorsky model, and at a higher field (when the domain walls merge), the system follows coherent rotation before reaching its saturation following the Stoner Wohlfarth model. Fu...

We have developed a mathematical tool able to track irreversible processes in magnetic systems described by the Stoner-Wohlfarth model, under any applied field history. A graphic representation is worked out that accounts for interactions, and turns out to be an extension of the one operating in the Preisach model. The response to alternating and rotating magnetizing fields have been investigated in detail. We have found a strategy in dealing with hysteretic memory effects which speeds the computational work needed to get the materials magnetization. This approach can represent a suitable tool aimed at estimate the energy loss and entropy production in magnetic systems.

In this paper, a new method to calculate the critical points (CPs) for a symmetric synthetic antiferromagnet, using the Stoner-Wohlfarth model for each layer is proposed. For given initial conditions, the system has multiple equilibrium states, and consequently, there are multiple energy barriers (EBs), so it is rather difficult to estimate the actual EBs for the real switches. Using the developed method, one can determine all the minimum energy points as well as the saddle points (SPs) based on the solutions of polynomial equations associated to the critical points conditions. These are necessary conditions to estimate the EB. Defining the EB as the difference between the lowest SP and the highest energy minimum for an applied field, one obtains for the lowest values of the EB the well-known critical curves. The plot of the EBs in the field planes is compared with the graphs of the critical curves and the results are discussed.

The existence of the five-fold twinned structures was observed in 3.4 nm FePt nanoparticles, and other n-fold structures were also been found in magnetic nano-grains in recording media. An analytical model, following the spirit of the Stoner-Wohlfarth model, is brought up to study the anisotropy field distribution of FePt or other magnetic nanoparticles with twinned or n-fold structures, based on simple statistical calculations of twin regions' volumes. It is found that the nanoparticle has an effective uniaxial anisotropy, and the average anisotropy field is substantially reduced compared to that of the single crystal. The calculated anisotropy distributions are also compared with the empirical distribution functions used in micromagnetic simulations.

SUMMARY The potential of using high-field anisotropy of isothermal remanence magnetization (hf-AIR) measurements for determining the origin of natural remanent magnetization in red beds and for identifying and correcting possible red-bed inclination shallowing was investigated for specimens of the Carboniferous Shepody Formation of New Brunswick and Nova Scotia, Canada. The technique makes it possible for a typical paleomagnetic laboratory to measure the remanence anisotropy of high-coercivity hematite. High-field (hf) AIR was used in conjunction with 100 mT alternating field (af) and 120 °C thermal demagnetization to separate the contribution of hematite to the remanence anisotropy from that of magnetite/maghemite and goethite, respectively. A 5-T impulse DC magnetic field was used for the hf-AIR to reset the magnetic moment of high-coercivity hematite so that demagnetization between AIR orientations was not necessary. The ability of a 5-T field to reset the magnetization was tested by generating an isothermal remanent magnetization acquisition curve for hematite by using impulse DC magnetic fields up to 5 T in one orientation and followed by applying a field in the opposite direction at each step. Each field application was treated by 120 °C heating and 100 mT af demagnetization before measurement. At 5 T, the difference between the magnetizations applied in opposite directions disappeared indicating that no magnetic memory persisted at this field strength. We performed a validity and reproducibility test of our hf-AIR measurement technique by measuring three specimens multiple times along two orthogonal coordinate systems. The method yielded highly reproducible results and, on rotating the specimen's coordinates, the fabric rotated by 90° as expected, showing that it is not an artifact of the technique. We also measured hf-AIR on samples that had previously been chemically demagnetized in 3N HCl to remove the secondary, chemically grown pigmentary hematite. The hf-AIR fabric of leached samples is similar to that of untreated samples, but shows a better-defined magnetic lineation and imbrication. We interpret the fabric observed for the Shepody Formation to be a compactional fabric that has been reoriented by strain during folding following a flexural-slip model.

Inversion of magnetic data is complicated by the presence of remanent magnetization. To deal with this problem, we invert magnetic data for a three-component subsurface magnetization vector, as opposed to magnetic susceptibility (a scalar). The magnetization vector can be cast in a Cartesian or spherical framework. In the Cartesian formulation, the total magnetization is split into one component parallel and two components perpendicular to the earth’s field. In the spherical formulation, we invert for magnetization amplitude and the dip and azimuth of the magnetization direction. Our inversion schemes contain flexibility to obtain different types of magnetization models and allow for inclusion of geologic information regarding remanence. Allowing a vector magnetization increases the nonuniqueness of the magnetic inverse problem greatly, but additional information (e.g., knowledge of physical properties or geology) incorporated as constraints can improve the results dramatically. Commonly available information results in complicated nonlinear constraints in the Cartesian formulation. However, moving to a spherical formulation results in simple bound constraints at the expense of a now nonlinear objective function. We test our methods using synthetic and real data from scenarios involving complicated remanence (i.e., many magnetized bodies with many magnetization directions). All tests provide favorable results and our methods compare well against those of other authors.

The physics of magnetic state change in single domain magnetic grains (called Stoner particles) is interesting from the fundamental as well as the applied points of view. A change in magnetization can be finely tuned with a specific time variation of an externally applied magnetic field. It may also occur naturally (without application of a field) at very low temperature with quantum tunneling and at higher temperature with thermal excitation. The optimal (usually shortest) time altering the magnetization along with the smallest applied magnetic field are sought in technological applications such as high-density reading or writing of information, spintronics, quantum information and quantum communication systems. This work reviews the magnetization change with a time dependent field and temperature and discusses the time it takes to alter the magnetization as a function of the control parameter chosen, temperature and material parameters.

Recent advances in high-density magnetic storage and spin electronics are based on the combined use of novel magnetic materials with conventional microelectronic materials (metals, insulators and semiconductors). A bit is stored as a magnetization state in some ferromagnetic material (FM) and controlled with an external field to alter the magnetization state. As device size is shrinking steadily toward the nanometer and the need to increase the processing bandwidth prevails, racing toward higher frequencies is getting even more challenging. In magnetic systems, denser storage leads to finer magnetic grains and smaller size leads to single magnetic domain physics. The Stoner–Wohlfarth (SW) model is the simplest model that describes adequately the physics of fine magnetic grains containing single domains and where magnetization state changes by rotation or switching (abrupt reversal). The SW model is reviewed and discussed with its consequences and potential applications in the physics of magnetism and spin electronics.

The model recently proposed by M.A. Chuev [JETP Lett.85, 611 (2007)] has been analyzed. It has been shown that the anisotropy corrections near the blocking temperature always lead to a magnetization lower than the equilibrium value, contrary to the findings in Chuev’s work. In addition, the asymptotic high-temperature limit of Chuev’s model is inconsistent with the expected thermodynamic limit. Moreover, even at a low temperature, only a careful implementation of this theory can guarantee arriving at the correct result, avoiding some wrong conclusions in Chuev’s work.

The REM(AF) method is a new tool for the analysis of the origin and alternating field demagnetization coercivity spectra of the remanent magnetization. We applied this method on precambrian Gila diabase sheets from Arizona in order to identify the high coercivity magnetic carrier, and on artificially shocked Rowley Regis basalt from UK in order to analyze the effect of the shock on the natural remanent magnetization. In the Gila diabase the high coercivity magnetic component was identified to be most likely represented by the acicular magnetite (increase in the efficiency ratio in the high coercivity region). In the Rowley Regis basalt, the REM(AF) analysis revealed that comparing to NRM, the shock produced a different distribution of the AF demagnetization coercivity spectra due to the occurrence of the Shock Remanent Magnetization.

The Stoner–Wohlfarth (SW) model is the simplest model that describes adequately the physics of fine magnetic grains, the magnetization of which can be used in digital magnetic storage (floppies, hard disks and tapes). Magnetic storage density is presently increasing steadily in almost the same way as electronic device size and circuitry are shrinking, and magnetism in general appears as a new contender for many novel computing applications that were considered traditionally beyond its range. Denser storage leads to finer magnetic grains and smaller size leads to magnetic grains so fine that they contain a single magnetic domain, i.e. a region in the material with a well-defined uniform magnetization best described with the mathematics of the SW model.

The quantum mechanical counterpart of the famous Stoner-Wohlfarth model -- an easy-axis magnet in a tilted magnetic field -- is studied theoretically and through simulations, as a function of the spin-size $S$ in a sweeping longitudinal field. Beyond the classical Stoner-Wohlfarth transition, the sweeping field-induced adiabatic change of states slows down as $S$ increases, leading to a dynamical quantum phase transition. This result is described as a critical phenomenon associated with Landau-Zener tunneling gaps at metastable quasi-avoided crossings. Furthermore, a beating of the magnetization is discovered after the Stoner-Wohlfarth transition. The period of the beating, obtained analytically, arises from a new type of quantum phase factor., 4 pages, 6 figures

International audience; Some soft magnetic materials are strongly dependent of the temperature, because of their low Curie temperature. In order to predict their behavior in electrical devices, engineers need hysteresis models able to take into account the temperature. This paper is an attempt to take into account 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. Simulation results are compared to measurements and discussed.

A model for the off-axis vector magnetization of a distribution of uniaxial particles is presented. Recent work by the authors decomposed the magnetization into two components and modeled the total vector magnetization as their vector sum. In this paper, to account for anisotropy, the direction of the reversible magnetization component is specified by the vector sum of the applied field and an effective anisotropy field. The formulation of the new anisotropy field (AF) model is derived and its results are discussed considering (i) oscillation and rotational modes, (ii) lag angle, and (iii) unitary magnetization. The advantages of the AF model are outlined by comparing its results to the results of the classical Stoner–Wohlfarth model.

The optimization in the design of the bit and word lines in magnetic random access memory is performed in the Stoner-Wohlfarth model. This is done by calculating the asteroid curves as a function of the angle between the bit and word lines. The calculation essentially involves finding the energy minima of the system. The switching field is reduced greatly when the angle between the bit and word lines is deviated from the right angles. Thermal stability of half-selected cells, which is estimated by calculating the energy barrier, is also improved significantly. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A preliminary study of paleomagnetism and rock magnetism has been done on 55 eclogite samples collected from the Chinese Continental Scientific Drilling (CCSD) site at the Maobei area, Donghai County, Jiangsu Province. Also the isothermal remanence, hysteresis loop, magnetic fabric, thermal susceptibility were measured, and analyses were made by electron-probe and scanning electric microscope on some samples synchronously. The result indicates that there are two groups of stable remanence, the normal and reversed magnetization. The remanence orientations are: D=94.3°, I=-29.1° and D=273.7°, I=15.4°, respectively. The magnetization intensity and the density of the samples which carry the normal magnetization are very different from those bearing reversed magnetization. The magnetic anisotropy is weak, and the minimum axis is hardly determined. The isothermal remanence and the hysteresis loop show that the magnetic carriers of the eclogite are likely SD (single domain) and PSD (pseudo-single domain) magnetite. According to the magnetic property, the cause of formation of magnetic carriers, the mechanism of the remanence, and the significance for the tectonics are discussed.

A method for the estimation of reversible and irreversible susceptibilities of initial magnetization curves has been developed. It deals with the energy necessary for magnetizing and demagnetizing the sample, but neither with the nature of the magnetization processes nor with a specific type of anisotropy, so it could be applied for a wide variety of real materials. A set of minor hysteresis loops of an initially demagnetized sample, plotted with progressively increasing maximum magnetic field, has been used. The obtained results showed excellent agreement with those calculated by the remanence curve method for a Stoner–Wohlfarth model system.

In order to develop a model of magnetic dynamics for quantitative analysis of the temperature dependences of the magnetization of an ensemble of nanoparticles in various regimes of the preliminary cooling of a sample, the phenomenological Stoner-Wohlfarth model is generalized for single-domain particles to the case of a more accurate description of relaxation processes in a magnetic system. Calculations in this model and their detailed analysis exhibit a number of qualitative features, including the asymptotic behavior of magnetization and susceptibility in the high-temperature limit, which is different from the Langevin limit for ideal superparamagnetic particles.

The effect of Ca-substitution on the physical and magnetic properties of Li0.3-0.5x Zn0.4Ca x Fe2.3-0.5x O4 ferrites (x = 0.0, 0.01, 0.02, 0.03, and 0.05), prepared by the standard ceramic method, has been studied. It is found that the saturation magnetization increases up to x = 0.01 and then it decreases. On the other hand, the initial permeability decreased while the Curie temperature remained almost constant with increasing x. The coercivity and remanence ratio increased with increasing x.

The magnetization reversal of the free layer was studied in a pseudo spin-valve Gd–Co/Cu/Co structure prepared by thermal evaporation. The uniaxial magnetic anisotropy in a plane of the film was induced by applying the magnetic field during deposition. The angular dependence of the free Co layer coercivity was observed to be consistent with the Stoner–Wohlfarth rotation model. The switching field of this Co layer was found to be dependent on an additional constant magnetic field, oriented perpendicular to the anisotropy axis in a plane of the multilayered structure. This dependence confirms the possibility of additional regulations of the sensitivity of the spin-valve structure by the application of an appropriate bias field and could be useful for sensor applications.

This paper presents an improved approach for simulating magnetic hysteresis, which takes into account the effect of applied stress, based on an extended Stoner-Wohlfarth (S-W) model. Meanwhile, the S-W asteroid rotates and shrinks, and the stable direction of magnetization of the particle can be calculated from the new energy minimum conditions. This developed model is applied to analyze the magnetic hysteresis phenomenon of a soft magnetic composite (SMC) material under different compaction process, and the results of simulations are in good quantitative agreement with experimental data.

In this work the magnetic behaviour of Fe-Si alloys is investigated at microscopic scale in order to better understand the physical mechanisms which govern the magnetization phenomena in such materials. The analysis is carried out on thin Fe-Si films with uniaxial anisotropy by means of both a micromagnetic simulator and the Stoner-Wohlfarth model. The conditions under which the Stoner-Wohlfarth approximation can be operated in reproducing the magnetization processes of anisotropic steel films are discussed.

A magnetic vortex is an in-plane circulation of magnetization around a nanometer-scale central core with out-of-plane magnetization pointing either up or down. Circulation of the magnetization, known as vortex chirality (VC), also has two possible states depending on the sense of circulation: clockwise (CW) and counterclockwise (CCW). Its potential for storing two units of information in a single cell lies in the fact that the polarities of the core and the VC states can be controlled independently [1]. However efficient and reliable switching of the core and chirality pose significant technological challenges.

Micromagnetics simulation leads to a deeper understanding of grain boundary phase effect by display of the magnetization reversal process in recent years[1]. But just minority research can reflect the microstructure of the material. Most of the simulation models use the theoretical microstructures which have a certain degree of approximation. This is why the simulation results are biased with the experimental results. Using Magnetic Force Microscope (MFM) image modeling method is applied in this paper, so that it can more accurately reflect the microstructure of the sample. And more precise hysteresis loop and magnetization reversal process can be studied.

This paper presents the scalar dynamic magnetic hysteresis model based on the Preisach theory. The important role in this theory played hysteresis operator states. The changes of these operators' states are not immediate in the dynamic model but they are a function of time and parameter k representing the magnetic properties of the material. In this paper the transient state of the hysteresis operator is defined by the nonlinear first order differential equation. The implementation of the dynamic hysteresis is additionally associated with feedback hysteresis model. This allows for obtaining a more accurate model for low and high magnetization frequencies. The material parameter k was determined for the toroidal tape wound core made of anisotropic sheet steel ET114-27. This paper presents the magnetic hysteresis loop simulation results for the different magnetization frequencies.

In this paper, a theoretical model has been established to study the contributions of the magnetization rotations to the magnetic properties of stressed amorphous magnetic films. The influences of both magnitude and direction of the applied stress on the magnetic properties have been discussed. The results show that the shapes of the hysteresis loops are significantly dependent on the applied stress. For amorphous magnetic film with positive magnetostriction, the longitudinal tensile stress can increase the coercivity but the remanence seems independent on the stress. Both the coercivity and remanence approach zero while the longitudinal compressive stress is large enough. The observed magnetostrictions of the amorphous magnetic films are influenced markedly by applied stress.

To study the nature of anisotropy effects in samples of polymer (PVA) films containing nanoparticles of magnetite the depth selective conversion Mossbauer spectroscopy (for layer-by-layer phase and magnetic analysis), saturation isothermal remanent magnetization (SIRM) and natural remanent magnetization measurements (NRM) in three mutual—orthogonal directions and atomic force microscopy were used. These investigations revealed formation of “in plane” direction of linear Fe 3 O 4 nanoparticles chains and their number increase with nanoparticles concentration growth in the samples. Significant influence of polymer matrix on macroscopic magnetic properties was revealed from the temperature dependences of saturation magnetization and Mossbauer spectra.

We present magnetic measurements on iron ( Fe ) nanoparticles in the size range 10–30 nm produced by the Inert Gas Condensation process (IGC). Structural characterization studies show the presence of a core/shell structure, where the core is bcc Fe while the surface layer is Fe -oxide. Analysis of the magnetic measurements shows that the nanoparticles display very large uniaxial anisotropy, K eff ≈3 - 4 × 106 erg/cc. The observed room temperature coercivities lie in the range ≈600 – 973 Oe , much larger than those expected from the Stoner–Wohlfarth model using the bulk iron anisotropy. It can be inferred from the coercivity variation with the particle size that there is a general trend of the coercivity increasing with size, culminating finally in a decrease for high sizes (30 nm) possibly due to the onset of non-coherent magnetization reversal processes.

easy axis and the critical field of the grain magnetic moment, i.e. the magnetic state of an individual particle. The nonmonotonic variation in the critical field due to an external eect can lead, in the presence of a magnetic field, to the formation of a remanence additional to the normal remanent magnetization (NRM) or, in the absence of the field, to the NRM destruction. Various types of remanent magnetization are compared within the framework of the model of interacting heterogeneous single-domain particles. It is shown that, in diagnosing thermoremanent (TRM) and chemical magnetizations, information on the ratios of these magnetizations to the anhysteretic magnetization should be complemented by data on the coercivity and the intensity of the magnetostatic interaction of grains. The possible variation in the spontaneous magnetization with time due to diusion

Dependence of magnetic properties on the angles between the applied magnetic field and the normal of the film plane in Co/Pt multilayer with easy magnetization direction perpendicular to the film plane have been studied. The results show that the sample exhibits unusual magnetization behaviors when an external magnetic field applied in different angle to the normal of the sample plane. The remanence decreases and the saturation field increases with increasing the angle, accompanying the magnetization-switching field and the coercivity enhance. These results suggest that the magnetization process in multilayers with perpendicular magnetic anisotropy (PMA) could not be described simply using coherent rotation model for uniaxial anisotropic ferromagnet.

In this paper, we illustrate that magnetic hysteresis affects the response of sensors based on magnetic phenomena and materials. Testing various magnetic techniques, we conclude that sensor uncertainty can be optimized by both the optimization of magnetic hysteresis and operation in the magnetically reversible area of the material. Preliminary modeling results are in agreement with our experimental findings.

The coercivity of magnetic thin film having a two-dimensional easy-axis distribution is investigated within the framework of a simple micromagnetic model. It is found that the coercivity decreases from 0.14H(K) to a minimum of 0.07H(K) as thickness increases, where H(K) is the anisotropy field. It is substantially lower than that given by the Stoner-Wohlfarth model and is consistent with available experimental data. The calculated hysteresis loop and the initial magnetization curve are also in good agreement with experiments.

We study the angular dependence of the exchange field and the coercivity of an in-plane exchange biased system in hysteresis loop measurements with the field applied out of the film plane by a Stoner–Wohlfarth model where the coherent rotation of the magnetization is assumed. The model shows an overall 1/cosψ dependence of both the exchange field and the coercivity, where ψ is the angle the applied field makes with the film plane. However, when ψ is close to 90°, the exchange field and the coercivity deviate from the 1/cosψ function. The coercivity in particular goes to zero when ψ approaches 90°. The principle and methodology of the model can also apply to other magnetic systems where the coercivity displays similar angular behaviour.