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The main scope of the paper is to apply the Design of Experiment (DoE) method and to develop a predictive model of energy losses for non-oriented electrical steels. This approach permits us to determine a mathematical model, which is the predicted response (energy losses) as a function of input data (strip width and peak magnetic polarization) and experimental results. The presented DoE model is based on a classical central composite design of type 2n + 2n + 1 with two-levels (n = 2) and as a consequence only nine experimental points are necessary. The equation system that is associated with the model, generates a surface response equation, which permits the energy loss computation for different values of width strip and peak magnetic polarization. The DoE model was implemented, using different software packages as MathCad, Excel and OriginPro 2018, in the case of two types of electrical steels namely NO20 and M300-35A alloys that are used in small size electrical machines. In this case, the strain hardening phenomena at the cut edge becomes important, due to its negative impact on energy losses. The computed results were compared with the experimental data and errors lower than 5 % were determined.

In this paper four non-oriented electrical steel grades M400-50A, M400-65A, M300-35A and NO20, utilizing a laboratory single sheet tester, were analyzed. For the magnetic measurements the peak magnetic polarization of 1 T was chosen. The frequency was variated between 3 Hz and 400 Hz. The isotropic electrical steel sheets were cut through punching technology, along the rolling direction. The experimentally determined energy losses were decomposed, using the loss separation theory, into hysteresis, classical and excess components. The relative magnetic permeability was analyzed and its parts, real and imaginary permeability were computed. The non-oriented alloy magnetic properties’ variation as a function of frequency was plotted and explained in the paper.

Due to worldwide regulations on electric motor manufacturing, the energy efficiency of these devices has to be constantly improved. A solution may reside in the fact that high quality materials and adequate cutting technologies should be carefully chosen. The magnetic properties of non-oriented electrical steels are affected by the cutting methods, through induced plastic, and thermal stresses. There is also an important correlation between chemical composition and different magnetic properties. In this paper, we analyze different industrial grades of non-oriented electrical steels, used in electrical machines&rsquo, core manufacturing as M800-65A, M800-50A, M400-65A, M400-50A, M300-35A, and NO20. The influence of the cutting methods on the normal magnetization curve, total energy loss and its components, and relative magnetic permeability is investigated in alternating currents using a laboratory single sheet tester. The chemical composition and grain size influence are analyzed and correlated with the magnetic properties. Special attention is devoted to the influence of the increased cutting perimeter on the energy losses and to the way it relates to each chemical alloy constituent. The final decision in what concerns the choice of the proper magnetic material and the specific cutting technology for the motor magnetic cores is imposed by the desired efficiency class and the specific industrial applications.

Two types of silicon iron steels, M400-65A non-oriented and MOH grain-oriented alloys were characterized using an industrial Brockhaus Single Strip Tester at two peak magnetic polarizations of 500 mT and 1000 mT in the frequency range from 10 Hz to 100 Hz. The samples were cut parallel to the rolling direction trough different cutting technologies, which are the classical mechanical-, then the non-conventional laser-, water-jet-and traveling wire electro-erosion methods. The loss separation concept was applied and the total energy losses, determined experimentally, for each sample were decomposed into hysteresis, classical (Foucault) and excess (anomalous) energy losses. A detailed analysis of each type of losses as a function of the frequency was made and the influence of the cutting technology was analyzed.

While the most promising longitudinal recording systems cannot surpass the theoretical limit of about 200 Gb/in2 for areal recording density and the demand for higher densities is permanently increasing, the perpendicular magnetic recording constitutes the realistic issue to the longitudinal one. The perpendicular magnetic recording offers significant advantages, the most important being stronger write and read fields, and therefore the use of media of higher anisotropy, smaller grain size, higher signal-to-noise ratio, and a better thermal stability. Unfortunately, the perpendicular recording has to cope some important physical and technological difficulties. To overcome them, many ingenious solutions were proposed. In this paper the coupled granular/continuous (CGC) media, a subtle association of the continuous and, respectively, granular media, are analysed from the viewpoint of their magnetic and recording properties. The challenges and possible improvements of CGC media are discussed.

Today high efficiency electrical machines are a new and mandatory trend in the motor production in Europe and United States of America. Lately there are developed also higher efficiency classes as IE4 (Super Premium Efficiency) and IE5 (Ultra-Premium Efficiency). It is well known that IE4 electrical motors are available on the market and IE5 machines are taken into account by several big producers. Efficiency upgrade of the motors has very good consequences on the environmental problems. The efficiency classes (IE1-IE4) are described in the international standard IEC 60034-30. Line-start permanent magnet machines and Squirrel Cage induction motors can be upgraded, in order to have a bigger efficiency, according to IE4 specifications. In the case of variable speed machines variable reluctance synchronous motors are also included in the efficiency class IE4. In order to improve a motor to comply with the IE5 efficiency NdFeB or Ferrite magnets should be used.

In this paper the hysteresis energy losses in two non-oriented industrial steels (M400-65A and M800-65A) were determined, by means of an efficient classical Preisach model, which is based on the Pescetti–Biorci method for the identification of the Preisach density. The excess and the total energy losses were also determined, using a statistical framework, based on magnetic object theory. The hysteresis energy losses, in a non-oriented steel alloy, depend on the peak magnetic polarization and they can be computed using a Preisach model, due to the fact that in these materials there is a direct link between the elementary rectangular loops and the discontinuous character of the magnetization process (Barkhausen jumps). To determine the Preisach density it was necessary to measure the normal magnetization curve and the saturation hysteresis cycle. A system of equations was deduced and the Preisach density was calculated for a magnetic polarization of 1.5 T; then the hysteresis cycle was reconstructed. Using the same pattern for the Preisach distribution, it was computed the hysteresis cycle for 1 T. The classical losses were calculated using a well known formula and the excess energy losses were determined by means of the magnetic object theory. The total energy losses were mathematically reconstructed and compared with those, measured experimentally.

Magnetization curve and energy losses have been analyzed in non-oriented (NO) Fe-Si alloys with variable thickness (0.20 mm–0.35 mm), cut at widths ranging between 5 mm and 60 mm, in order to assess the impact of cutting, either done by punching or water-jet techniques. Measurements were performed by means of a digitally controlled single strip tester, from dc up to 1.5 kHz, at peak polarization values Jp = 1.0 T and 1.5 T. The evolution of the magnetization curve and the structure-dependent hysteresis Wh and excess Wexc loss components have been assessed as a function of the strip width using a simple phenomenological model, by which the extension of the damaged area at the edges of the cut sheets is estimated. Such a model assumes a hyperbolic dependence of the measured polarization on the cut strip width. The limiting values of Wh and Wexc for the fully damaged and the pristine sheets are in this way estimated, showing that one can simply and affordably predict the magnetic behavior of NO Fe-Si steels subjected to cutting.

In electrical machine production, the mechanical cutting procedure induces plastic deformation and mechanical stresses, which are directly linked to the magnetic properties’ degradation. In spite that the non-oriented electrical steel has a small magnetocrystalline anisotropy, the influence of the easy and hard magnetization axes on the magnetic permeability and energy losses is important. In this study we present a mathematical model, used for the damaged zone width estimation that results from the mechanical punching procedure. Through this technological cutting method NO20 non-oriented electrical steel strips of 300 mm × 30 mm were prepared, being cut parallel (RD) and normal (TD) to the rolling direction. The Epstein standard sample 30 mm in width was reconstructed, by putting together strips having their width in an interval between 5 mm and 30 mm. These samples were assessed utilizing a laboratory Single Strip Tester (SST) for frequency ranging from 3 Hz to 400 Hz, at J p = 1 T (peak magnetic polarization value). Using the statistical theory of losses (STL) total energy losses were decomposed into hysteresis, classical and excess losses, and their variation was investigated as a dependence of the strip width.

We report an investigation on the improvement of magnetic properties in crystalline silicon iron alloys. It was studied the influence of three thermal treatments on the energy losses of non-oriented silicon iron (NO FeSi) sheets, M800-65A industrial grade, at two peak magnetic polarizations 0.5 T and 1 T. First treatment was done at 200 °C for 60 minutes, the second treatment at 550 °C for 30 minutes and the third treatment at 700 °C for 10 minutes. In the case of grain-oriented silicon iron (GO FeSi) sheets, 30Z140 industrial grade, was analyzed the influence of laser scratching on the magnetic properties at peak magnetic polarization 0.25 T. In the case of both steel grades is presented the reduction of the hysteresis, classical and excess losses, that occur after the applied treatments, using the concept of energy loss separation.

Non-oriented silicon iron (NO Fe-Si) alloys are soft magnetic materials used in the construction of medium and high power rotating machines. To obtain efficiency higher than 95%, it is necessary to promote a new design of their magnetic circuits and/or alternative cutting technologies. There were tested steel samples of fully processed non-oriented silicon iron (NO FeSi) grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a single strip tester in the range of frequency from 10 ÷ 200 Hz at 1 T peak magnetic polarization. The sheet cutting technologies, involved in this study, are mechanical, laser, water-jetting and electro-erosion.

Grain-oriented electrical steels are used in electrical vehicle traction, electric devices such as special motors, transformers and actuators. This type of material presents a strong magnetocrystalline anisotropy that has an important influence on the energy losses and other magnetic properties. It is well known that the classical grain-oriented material has a (110)[001] Goss texture and this structure is produced by a secondary recrystallization with a 3 to 10 mm grain size. The best magnetic behavior of the strips is observed along the crystallographic axis, which is called easy magnetization direction. The worst magnetic properties are determined at an angle of 55° ( ) with the rolling direction. The influence of the anisotropy is analyzed on samples cut at different angles starting with 0° in step of 15° up to 90°. The samples were cut through a classical mechanical punching, and two non-conventional methods: electro-erosion and laser. The energy losses were measured by means of an industrial Brockhaus single strip tester, in the frequency range from 10 Hz to 100 Hz at a peak magnetic polarization of 1T. The loss separation concept was applied, and the magnetocrystalline anisotropy influence on the hysteresis, classical and excess losses was analyzed.

Nowadays electrical machines are the most important electricity consumer, because they are responsible for 70% of industrial demand. The improvement of the electrical machines' energy efficiency can be done among other methods, by using high quality non-oriented electrical steels. High efficiency electrical machines are considered a new trend and are gradually imposing themselves in motor manufacture worldwide. Efficiency upgrade of motors could have a positive impact on the environment, being well known that IE4 electrical motors are already available on the market. In the paper there were tested samples of M400–50A and N020 industrial steel grade, cut through mechanical and water jet technologies. The samples have a 300 mm length and a variable width comprised between 5 mm and 30 mm. To reconstruct the standard Epstein width of 30 mm, 2, 3, 4 and 6 samples were put together side by side. In order to determine the magnetic properties, a single strip tester was used. The energy losses and the relative magnetic permeability were analyzed as a function of frequency in the range of 10 Hz-400 Hz at a peak magnetic polarization of 1T.

The B-H characteristic of an iron body material influences the magnetic field measured in the air. On principle, one can pose the problem of B-H relation determination, by making measurements of the magnetic induction in the neighbourhood of the body. Unfortunately, we have an ill-posed inverse magnetic field problem, for which there is possible that, big variations of the BH characteristic to produce only very small modifications of the magnetic field in the air. It is essential to use a sufficiently sensitive computation procedure in order to produce credible results. This paper proposes a device for the B-H characteristic evaluation, admitting that inside the ferromagnetic bodies the magnetic field distribution is not uniform.

We report an investigation and a theoretical assessment of energy loss prediction in crystalline and amorphous soft magnetic materials. There were tested a sample made from non-oriented silicon iron (NO FeSi) M800-65A, industrial type alloy, cut longitudinally to the rolling direction and a toroidal sample of Co67Fe4B14.5Si14.5amorphous ribbon. The losses behaviour of the crystalline NO FeSi strip was studied as function of frequency in the range of 5 Hz to 200 Hz at a given magnetic polarization (Jp) of 0.5 T and 1 T. In the case of the amorphous Co-based ribbon the losses variation was studied as function of frequency in the range of 5 Hz to 10 kHz at a given magnetic polarization of 20 mT. Using the concept of loss separation for the data analysis, in the approximation of linear magnetization law and low frequency limit, it can be considered in both cases, that the excess losses can be quantitatively assessed within the theoretical framework of the statistical loss model based on magnetic object theory.

Good operation of power transformers is very important because they are among the most expensive equipment in the network generation, transmission and electricity distribution. It became necessary regular monitoring of such systems and determinate the life of a transformer, it preventing breakdown and corresponding loss occurrence.Ageing in the insulation system of power transformers is determinate by influence of air, moisture, temperature, mechanical and electrical stresses and insulation contamination. One of the most important ageing indicators in transformers is the water content in the solid part of the insulation. The water reduces drastically the dielectric strength of solid insulation, accelerate ageing in paper and can cause water vapor bubbles.In RVM method a voltmeter determines the recovery voltage (RV) after charging the insulation with a DC voltage. By subsequent relaxation and repeated charging for varied times the so called polarization spectrum can be created. RV range provides an indication on the condition in which there is the insulation of transformer. The paper analyzes measurements on two high power transformers in operation, determining the moisture content of solid insulation.

The conventional magnetic recording has approached its physical limits. Further growth of the areal density is limited by the superparamagnetic effect and by the limited possibilities to further improve write heads design and pole materials in order to enhance the writing field. A new technology proposed to surpass these limits is theheat assisted magnetic recording(HAMR). The principle of HAMR and the structure of a HAMR system are discussed, as well as the processes characterizing the writing process and the requirements for the materials needed for this type of recording. Some important challenges of the HAMR technology are summarized.

Solution of the equation of motion for conductors in external magnetic fields requires the knowledge of the magnetic forces due to the induced eddy currents that, in turn, can be determined if the position and the velocity of the bodies are known. An iterative technique is adopted, where, at each time step, an initial value of the magnetic force is used to determine the position and the velocity of the body at the end of the time step and, then, the value of the force is corrected. To reduce the computational effort in the case of thin metallic sheets, it is proposed to use the surface integral equation of the induced eddy currents, with a supplementary term added to account for the motion. A sinusoidal with time variation of the excitation field is considered and a phasor representation of various physical quantities is employed. An average magnetic force over each period is used to solve the equation of motion.

As electric insulators of the copper conductors in the electric generators of alternative current or in electric motors of high tension, there are used with priority the composite crosslinked mica-epoxy. Pre-impregnated band with solvent was introduced, the impregnation being performed with phenolic-novolac resin. The studied material got superior dielectric properties at function temperatures corresponding to the insulation class F(155C). Its main components are: mica paper (53%), glass cloth (13%) and the basic epoxy phenolic-novolac resin. The complex permittivity and conductivity were determined with the Time Domain Spectrometer (TDS); the apparatus allows the determination of the electric values in the domain of frequencies: very large domain of frequencies. The temperature varied in the domain 23-190C with the help of an oven. The purpose of this article is to report the dielectric properties of mica-epoxy-novolac composite insulator, for which very few data have so far been published.

The magnetic anisotropy in grain oriented FeSi alloys (FeSi GO) is very important nowadays, because these steels are usually used for their very good magnetic properties along the rolling direction (RD). In electrical devices the steel magnetic core is subjected to flux lines that are making an angle, different from 0° to the RD and to 2D magnetic flux densities. In the paper there were analyzed samples of a commercial FeSi GO M0H steel industrial grade cut through mechanical punching and electro-erosion technologies. The investigated samples have a thickness of 0.3 mm and an area of 300 mm × 30 mm and were cut at angles θ ranging between 0° and 90° at 15° intervals with respect to the RD. The magnetic characterization was performed with a standardized unidirectional Single Strip Tester (IEC 60404-7) and a frequency analysis from 10 Hz to 100 Hz was done, in order to investigate the energy loss behavior. The loss separation concept was applied, to determine the influence of the cutting technology on the m...

In this paper is point out the influence of the classical mechanical cutting on the magnetic properties of three industrial non-oriented electrical steels M400-50A, M400-65A and, M700-50A. The selected materials were magnetically characterized and analyzed at 50 Hz and at a peak magnetic polarization J P ∈ {50, 100, 250, 500, 800, 1000, 1100, 1200, 1300, 1400, 1500} mT. Based on the complex permeability concept, in which the total permeability is divided into two parts, the real and the imaginary component, the measured values are presented. All the investigated strips have a length of 300 mm and, to magnify the degradation, a decreasing width of 30, 15, 10, 7.5 and 5 mm were chosen. The magnetic characterization was performed on a laboratory single strip tester (SST) set-up, which can make standardized measurements on samples with an area of 300 mm × 30 mm. To reassemble the standard width of 30 mm, there were put together side by side 2, 3, 4 and 6 pieces.

The use of high quality non-oriented electrical steel and of an innovative design for the magnetic cores of the electrical machines are very important, in order to minimize the value of the total energy losses. The energy losses are strongly influenced by the cutting technologies, and the producers of the electrical machines want to minimize the deterioration of the magnetic properties during the manufacturing process. The influence of the cutting density on the magnetic permeability and energy losses was analyzed and one can notice that these magnetic properties are strongly influenced by the cutting technologies. There were tested sheet samples of M400-50A and M700-50A industrial steel grades (thickness of 0.50 mm), cut through mechanical and water jet technologies. All samples have the length equal to 300 mm and the width of 30, 15, 10, 7.5 and 5 mm. The magnetic characterization was performed using a laboratory single strip tester, which can make measurements on samples with an area of 300 × 30 mm2. I...

In this article it is presented a study of the magnetic anisotropy of non -oriented and grain oriented Fe-Si strips with the surface area of 280 x 30 mm 2 . The measurements were performed with a unidirectional single strip tester on Fe -Si strips cut at 0, 15, 30, 45, 60, 75, 90 with the rolling direct ion. For the representation of the magnetic field strength at constant magnetic flu x density it was used a software program that interpolated the experimental results. It was determined the hard and the easy axis of the samples and the influence of the frequency on the anisotropy of the materials.The loss behaviour of these alloys was studied as a function of frequency in the range of 5 Hz to 200 Hz at a given magnetic polarization (Jp) of 1 T and using the concept of loss separation for the data analysis it was given a correlation between the different types of losses and the anisotropy axis.

Water jet technology that uses abrasive particles is an efficient cutting method, for electrical steels and it has many advantages, by comparison with the classical punching. During the cutting process there are not any heating phenomena and the method has a high versatility with a minimum applied stress on the work piece. There were tested strip samples of M400-50A, M400-65A, M700-50A and M700-65A electrical steel grades cut through water jet technology. The samples' length is equal to 300 mm and their width is set to 30, 15, 10, 7.5 and 5 mm. The magnetic property measurements were performed with a laboratory single strip tester (SST), which can characterize only samples with an area of 300 mm × 30 mm. Thus, to reconstruct the standard width of 30 mm, there were put side by side 2, 3, 4 and 6 pieces with the same width. The magnetic quantities were investigated at 1000 mT in the frequency range 10 ÷ 100 Hz. This type of non-conventional cutting method proves to have a low influence on the energy losses with respect to the increase of the cutting perimeter, because during the cutting process the edge damage is limited to a very narrow width.

The paper presents a comparative study of two magnetic materials: Co-rich nanocrystalline and amorphous films of the same compositions, obtained by electroplating at different current density. The electrodeposited Co-rich alloys formed at 20–30 mA/cm2 are nanocrystalline and have the same magnetic behavior and a good stability.

The conventional magnetic recording approached the physical frontiers of the recording density. The magnetic recording must face the famous trilemma: In order to increase the recording density, smaller grain volumes are needed, but in order to ensure the thermal stability of recorded information, the anisotropy constant should be increased accordingly; what results is an increased anisotropy field, which requires higher writing fields. Such fields are unavailable with the maximum saturation magnetization obtainable with the magnetic materials of the current heads. In order to overcome these problems, new media structures have been proposed. The most promising is the bit-patterned magnetic media (BPM), intensively studied over the last years with the aim of obtaining obtain an ultra-high recording density of hard-disk drives. A BPM comprises monodisperse high-anisotropy nano-particles in a self-organized patterning. They have a higher thermal stability, a lower noise and a higher signal resolution, which leads to a higher recording density and a better SNR. They eliminate the transition noise and, due to the large fraction of the bit volume occupied by the magnetic dots, improve thermal stability. Nevertheless, some important issues such as long-range patterning, control of the surface roughness, signal readout, etc., remain critical problems to solve. Another challenge is the fact that recording on BPM is sensitive to the material and geometry parameter fluctuations that may lead to additional constraints and require tight synchronization of the write-field misregistration time and bit positions. A possible route to higher recording densities is to use a multilevel recording, where more than two states are stored per dot.

Mechanical cutting technology is a worldwide method, used to cut the magnetic cores of the electrical machines nowadays. The manufactures of the electrical devices prefer cutting the non oriented steel through this classical method, due to the fact that it is the cheapest of all. Non oriented silicon iron alloys (NO FeSi) are mainly characterized by specific energy losses. The mechanical properties and the coatings of the material become important, because they influence the power density and the cost of the resulting electric machine. There were tested strips of M800-65A industrial steel grade, cut through punching technology. All samples have the length equal to 300 mm and the width of 30, 15, 10, 7.5 and 5 mm. The magnetic characterization was performed using a laboratory single strip tester, which can make measurements on samples with an area of 300 × 30 mm2. To have the standard width of 30 mm, there were put together side by side 2, 3, 4 and 6 pieces with different widths. The magnetic properties were analyzed at 1000 mT and 1500 mT in the frequency range 10 ÷ 200 Hz.

The standard magnetic measurements, for grain oriented (GO) and non-oriented (NO) electrical steels (FeSi), are made using the Epstein frame or the single strip tester. The magnetic characterization is limited to the rolling direction cut samples for the FeSi GO materials. For the NO ones, the standard measurements give an average of the magnetic behavior in the rolling and the transverse directions. In this article is analyzed the magnetic anisotropy of FeSi NO and FeSi GO strips, with the surface area of 300 × 30 mm2. The measurements were performed with an unidirectional single strip tester on FeSi strips cut at 0°, 15°, 30°, 45°, 60°, 75°, 90° with the rolling direction. It was determined the hard and the easy axis of the samples and the influence of the anisotropy on the energy losses and relative magnetic permeability. The loss behavior of these alloys was studied as a function of frequency in the range of 5 Hz to 200 Hz at a given magnetic polarization (J p ) of 1 T.

Nowadays it is very important to use non-oriented electrical alloys, which must have a very good quality and must be cut through a proper method that leads to a minimum energy loss value. The manufacturers of the electrical machines want to minimize the damage of the magnetic properties during the cutting process, in order to produce high efficiency motors or generators. In this paper are presented two non-conventional cutting technologies, which are used in the prototype production of the magnetic cores. These two methods have significant effects on the area near the cut edge; the water jet produces important burs and oxidation of the material and the laser cutting generates high local thermal stresses that increase the total energy losses of the magnetic core. There were tested steel samples of fully processed non-oriented alloys (NO FeSi) grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a laboratory single strip tester in the range of frequency from 10 ÷ 400 Hz at 1 T peak magnetic polarization.

Punching and laser cutting of non-oriented silicon iron sheets (NO FeSi) determine changes in the material at the cutting edge, which produce an important effect on the magnetic properties. Through punching it results a plastic deformation in the zone near the cutting edge. Laser cutting technology causes thermal stresses, which alter also the magnetic properties. The knowledge of the type of deterioration is very important for the production of the electrical machines, because of the increased total losses. There were tested steel samples of NO FeSi grades, M400-65A and M800-65A, with an area of 300 × 30 mm2. The magnetic properties were measured with a laboratory single strip tester in the range of frequency from 10 ÷ 400 Hz at 1 T peak magnetic polarization.

The behaviour of thin magnetic films with uniaxial anisotropy and exhibiting an open Kittel-type domain structure is studied in the transient state resulting from the application of a low step magnetic field. Quantities describing the local and the mean magnetic field are calculated taking into account the domain structure of the sample and the hypothesis of wall pinning on the faces of the film. The different kinds of losses are analyzed. Also, when applying an external field of suitable form, the factors determining the shortest possible response time of the system are established.

We have investigated the magnetic and structural properties of polycrystalline Ni-Zn ferrite thin films with thicknesses of about 1000A. The films were prepared by R F sputtering deposition in 1.5×10 -3 mbar argon atmosphere, using targets with nominal composition Ni 0.7 Zn 0.3 Fe 2 O 4 The effects of substrate temperature and post deposition heat treatment of thin films were examined. The X-ray spectra of Fe-Ni-Zn oxides deposits reveal the formation of spinel phase of Ni-Zn ferrite, that is characteristic for these materials. only for temperatures higher than 500°C. TEM and ED indicate that the initially amorphous thin films, deposited at 100°C, become polycrystalline by heat treatment. The grain size of the crystallites is 800A to 1000A for Ni-Zn ferrite thin films annealed at 900°C. V.S.M. measurements show coercive fields of 12 kA/m for thin films annealed at 900°C. which are larger than those found for Ni-Zn ferrite targets. This value of coercive field is related to the shape anisotropy originated by the film microstructure and with the increase in the number of low angle grain boundaries, which act as pinning sites for domain walls. Saturation magnetization values of 220-250mT for Ni-Zn ferrite thin films are higher than half of bulk values.

Local coordinate systems are attached to the conducting bodies in motion which allows the usage of the eddy-current integral equation to determine the electromagnetic field. The space discretization is performed only for the conducting bodies and remains unchanged in time. An additional term, similar to the “motional” electromotive force in Faraday's law, is introduced in the integral equation. If the imposed currents are sinusoidal with time, a phasor representation is employed for a frequency-domain analysis based on the eddy-current integral equation. Since the “electrical” period is much smaller then the “mechanical” period of the body vibration, the time average force over an “electrical” period is used in the equation of motion. This allows for the solution of the equation of motion to be obtained by employing a time step which is greater than the “electrical” period. Thus, the efficiency of the method presented is much greater than the efficiency of the time-domain methods, where the time step is chosen to be a small fraction of the “electrical” period. This is more so at higher frequencies, which are used for more efficient levitation devices.

A new object-oriented software, which is dedicated for the characterization of magnetic materials, including the hysteresis effect, is presented. The product allows the development and utilization of an information base, containing experimental and numerical data related to the magnetic material behaviour. The materials may be modelled with different hysteresis models (Preisach, Jiles-Atherton, etc.).