Search

Mu-metal is used to shield highly sensitive machines against magnetic noises. Magnetoencephalography is an application that uses mu-metal to construct a magnetically shielded room (MSR). Each layer of a multi-layer MSR is exposed to a different strength of magnetic noise. The outer layers are exposed to higher noise levels, whereas the inner layers are exposed to lower noise levels. The mu-metal in each layer of the MSR is required to have different magnetic properties depending on the magnetic noise level to which it is exposed. In this study, we propose the use of the index of permeability $\mu $ under a very-low-frequency micromagnetic field to evaluate the magnetic properties of mu-metals used in the innermost layer of the MSR. A measurement system for $\mu $ is outlined in this article. Measurements were conducted using different heat treatments. Three test pieces (TPs) of the mu-metal from the same lot were heat-treated in a hydrogen atmosphere and subjected to different isothermal conditions and cooling rates. The measurement results demonstrated that the TPs exhibited different magnetic properties at very slow micromagnetic fields, and the properties of the mu-metal could be controlled by heat treatment.

There is an increasing need to shield beams and accelerator elements from stray magnetic fields. The application of magnetic shielding in linear colliders is discussed. The shielding performance of soft iron and mu-metal is measured for magnetic fields of varying amplitude and frequency. Special attention is given to characterise the shielding performance for very small-amplitude magnetic fields.

This study introduces a deep analysis, which correlates the metallurgical characters with the magnetic properties in laser powder bed fusion processed Ni-Fe-Mo, to produce 3D prototypes with maximum magnetic shielding performance for ultra-sensitive quantum-based systems. The study conducts a sequenced plan of optimising the magnetic properties via microstructure density control, controlling the magnetic anisotropy, before applying heat treatment (HT) and hot isostatic pressing (HIP) post-processes. This is also considering delivering effective mechanical properties. The magnetic properties optimisation was performed via laser parametric study, which found that the sample built with laser energy density E = 4.68 J/mm2 achieves the best soft magnetic and mechanical results due to the lowest defects. However, the obtained magnetic properties are still poor, due to the (001) rich grain orientation, which parallels the hard axis of magnetisation in this alloy. It was found that tilting the crystallographic orientation of the as fabricated (AF) optimised condition with 45˚ and 35˚, with respect to the build direction, improves the soft magnetic properties, as these angles correspond to the easy axes of magnetisation and , respectively, allowing the grain orientation in the same directions. The magnetic properties are further promoted with HT and HIP post-processes application. The magnetic shielding results of hollow tubes, built with the same optimised condition, confirmed the magnetic behaviour of the bulk coupons, achieving 83% of the commercial magnetic shielding.

The effects of the substitution of nickel for iron on the magnetic properties, uniaxial anisotropy induced by magnetic field, and crystallization process of the nanocrystalline Fe72.5–x Ni x Cu1.1Nb1.9Mo1.5Si14.3B8.7 FINEMET alloys modified with molybdenum have been studied. Nickel additions of up to 3 at % have been shown to increase the Curie temperature and magnetization of the alloy, whereas nickel additions of more than 6 at % lead to the decrease in these parameters as compared to those for the initial nickel-free alloy. Nickel additions of 6‒7 at % cause a linear increase in the induced uniaxial magnetic anisotropy constant. Nickel additions of more than 6 at % restrain the crystallization of the alloy and lead to substantial decrease in its magnetic hysteresis characteristics.

The influence of magnetic filler on magnetic and physical–mechanical properties of composite samples with the concentration varying from 100 to 600 phr (i.e., 17–55 vol.%) was studied. Magnetic polymer composites were synthesized by incorporation of soft magnetic filler in acrylonitrile-butadiene rubber matrix. Soft magnetic lithium ferrite powder substituted by Zn and Ti having the chemical composition Li0.525Zn0.30Ti0.35Fe1.825O4 with the addition of 0.005 Bi2O3 and 0.05 MnO2 prepared by the standard double-sintering ceramic process was used as the magnetic filler. Structural and magnetic characterization of Li ferrite carried out by means of X-ray diffraction analysis and measurement of the temperature dependences of magnetic susceptibility confirmed the single-phase cubic spinel structure of ferrite with Curie temperature $T{_{C}}=324~^{\circ }\text{C}$ . Fundamental magnetic parameters obtained from hysteresis loops confirmed the soft magnetic behavior of the ferrite filler. Magnetic properties of synthesized composite samples were evaluated from complex permeability measurements $\mu =\mu '-j\mu ''$ in the frequency range from 10 MHz to 6.5 GHz. Observed results acknowledged that the amount of lithium ferrite remarkably affects the properties of magnetic polymer composites, i.e., increasing ferrite filler amount caused increase of magnetic permeability as well as the hardness and elongation at break; on the other hand, the values of tensile strength at break decreased.

Soft magnetic materials are used in integrated power magnetic devices (such as micro-inductors and micro-transformers) to achieve reasonable inductances at frequencies over a few megahertz. However, the out-of-plane (perpendicular) anisotropy, in thick films produced by vapor deposition, worsens the in-plane soft magnetic properties. This paper reports on the nano-lamination of Permalloy (Ni $_{81}$ Fe $_{19}$ ) thin films with the introduction of nitrogen-doped tantalum in between to eliminate the out-of-plane anisotropy and improve the in-plane anisotropy. This significantly improves the in-plane soft magnetic properties, reducing the coercivity from 1352 A/m to 25.5 A/m and increasing the anisotropy field from 180 A/m to 660 A/m. The high-frequency permeability was uniform up to 500 MHz, and the ferromagnetic resonance (FMR) frequency was increased to 1 GHz. These properties are ideal for high efficiency magnetic applications at high frequencies and an extended FMR frequency is imperative for gigahertz-range devices.

The causes of changes in the magnetic properties of an amorphous Co–Ni–Fe–Cr–Si–B alloy obtained by melt spinning in the form of a thin ribbon subjected to heat treatment and subsequent action of temperatures corresponding to various conditions of its exploitation have been analyzed. We have established the regimes of heat treatment that provide for the highest values of the maximum magnetic permeability of the alloy and the shielding factor of a magnetic shield made from the alloy. We have analyzed changes in the magnetic properties, shielding properties, and total magnetization distribution in an alloy ribbon at a temperature well below the crystallization temperature. We have found the temperature ranges that determine the practical application of this alloy.

In this paper, a multilayer thin-film giant magnetoimpedance (GMI) magnetic sensor is fabricated, and its performance is enhanced by post-processing treatment. The CoSiB alloy is developed to enhance the performance of multilayer thin-film GMI sensors. The material is studied for different post-processing magnetothermal conditions. The provided recipe will facilitate low-cost fabrication of GMI structures in conventional microfabrication facilities. A detailed study is carried out to investigate the effect of temperature, time, and external magnetic field on the results of the post-processing technique. The prepared samples are tested with various magnetics and material characterization tools in order to give a detailed understanding of these effects. The post-processing shows a significant impact on the magnetic properties of the material. It is demonstrated that some nanoclusters of cobalt (with a diameter of 2–4 nm) form in its amorphous matrix structure, enhancing the permeability of the material.

The magnetic shielding capability of bulk MgB2 hollow cylinders can be fruitfully combined with an external paramagnetic sheath, to tailor the shape of the external magnetic flux lines. By appropriate selection of the external sheath permeability and thickness, it is possible to leave the magnetic flux lines unaltered by the shield (cloaking effect). Preliminary measurements have been performed at 4.2 K on shielding capability of bulk cylinders, which are subjected to axial and transversal magnetic fields up to 5 T. The cloaking conditions have been modeled to find the optimized thickness to realize the cloaking effect. The MgB2 material of the superconducting shield is also optimized to avoid low-temperature flux jumps, without losing its shielding capability.

Magnetic fields can be effectively shielded with superconducting tapes. They can be used either to attenuate a magnetic field or to improve its homogeneity. In this paper, magnetic field changes, due to the presence of a superconducting shield, are investigated. Both experimental and model results are shown. Specimens were subjected to a low-frequency ac magnetic field (up to 45 Hz). Attenuation of the field inside a shielded cavity was observed. The dependence of the shielding effect on the magnetic field strength and frequency was analyzed. A computer model of a shield has been developed. The additional increase of the shielding effect was observed above a certain threshold frequency depending on the geometry and material properties of a screen. The size and limits of this increase were investigated. It was observed to be linear in some frequency intervals. The interval of magnetic field amplitude, in which magnetic field attenuation is constant, becomes thinner at higher frequencies. Analyzed shields may find multiple applications in devices where dc and low-frequency magnetic fields are present. Their construction is uncomplicated, and they are relatively cheap. Medicine and science can greatly benefit from this simple and reliable method of magnetic field attenuation.

The microwave permeability in a soft magnetic FeCoB film as a function of the external magnetic field is measured in the frequency range from 0.2 to 8 GHz. When the field applied parallel to the orientation of the magnetization varies from 90 to −90 Oe, the permeability spectrum shows hysteretic behavior. Double magnetic resonance peaks come forth and evolve in the imaginary part of the permeability when the field approaches the coercive field of the sample. This phenomenon is attributed to the formation of domains, the resonance frequency of the reversed domains being different than that of the non-reversed domains. Both peak frequencies and peak amplitudes are interpreted quantitatively using simple considerations based on the Landau–Lifshitz equation and the knowledge of the static magnetic properties of the film. The ratio of the reversed magnetic moments to the non-reversed ones is estimated by fitting curves of the permeability spectrum.

The magnetic and magnetotransport properties have been investigated in a family of multilayer glass-coated microwires with a soft CoFeSiB nucleus and magnetically harder Co and CoPtRh deposited outer layers. Their magnetic properties are mainly determined by the magnetic interactions between the magnetic phases, i.e., the magnetoelastic coupling generated by the supplementary mechanical stresses induced by the deposited layers and by the magnetostatic interactions between the soft magnetic inner core and the hard magnetic deposited layers. The deposition of 900 nm-thick hard magnetic layers (Co and CoPtRh) on the soft magnetic CoFeSiB glass-coated microwire leads to a biphase magnetic character. Isothermal annealing at 300 °C for 1 h of multilayer microwires determines a slight decrease of the coercive field, an increase in the relative magnetic permeability, and to an increase in the magnetoimpedance response, more significant for the CoFeSiB/Co multilayer microwires. The possibility to design the magnetic and magnetotransport properties through magnetic coupling and annealing makes these materials very competitive as the functional sensing elements.

Flake-shaped Fe–Si–Cr alloy powders were prepared by crushing alloy ingots and the ball milling method. Magnetic properties of Fe–Si–Cr alloy powders with the nominal compositions of Fe81.4+ x Si17– x Cr1.6 ( $x=0,2,4$ , and 6) and the different values of milling time (0 to 120 h) were investigated. A scanning electron microscope, X-ray diffraction, and a vibrating samples magnetometer were used to characterize Fe–Si–Cr alloy powders. It is observed that, with the increase of parameter $x$ , the permeability of Fe81.4+ x Si17– x Cr1.6 ( $x=0$ , 2, 4, and 6) powders first increases and then decreases in 0.5–2 GHz, meanwhile the peaks of the imaginary part of the magnetic permeability ( $\mu ''$ ) transfer to the lower frequency in 0.5–6 GHz. The saturation magnetic ( $M_{S})$ and the coercivity ( $H_{C})$ were also investigated. The value of $M_{S}$ increases from 110 emu/g ( $x=0$ ) to 148 emu/g ( $x=6$ ), while the value of $H_{C}$ changes in the opposite trend from 30.7 Oe ( $x=0$ ) to 25.5 Oe ( $x=6$ ). For Fe85.4Si13Cr1.6 alloy powders with the increase of milling time, the peaks of $\mu ''$ transfer to the higher frequency, while the values of $\mu ''$ first increase and then decrease in 0.5–10 GHz. We attributed this to the change of the aspect ratio. A large aspect ratio increases planar anisotropy, which can enhance the magnetic permeability of the material. It is observed that the imaginary part of the magnetic permeability is 3.91 with $x=4$ and milling time $= 48$ h at 1.1 GHz.

Soft magnetic alloys have been widely applied to modern technology devices, such as transformer cores, choke coils and inductive devices. Magnetic field annealing can induce an uniaxial magnetic anisotropy K u [1-4] so as to improve the soft magnetic properties of alloys for the purpose of coping with different application requirements. So far, FeCo-based nanocrystalline alloys have been explored increasingly in order to improve the magnetic softness at higher temperatures[5-6]. Furthermore, the effect of magnetic field annealing on FeCo-based alloys is more pronounced compared with that of single ferromagnetic element composition [7-8]. Therefore, to explore the optimal magnetic field annealing method of FeCo-based alloys can effectively improve their soft magnetic properties to adapt to more strict application requirements at high temperature conditions. Magnetic field annealing of nanocrystalline alloy mainly includes three methods [9-11]. (a) The direct magnetic field annealing above the crystallization temperature of initial crystalline phase T x1 (magnetic field nanocrystallization). (b) Annealing above T x1 for nanocrystallization without magnetic field and then longitudinal magnetic field annealing below the Curie temperature of amorphous phase T c am. (c) After nonmagnetic field annealing above T x1 followed a magnetic field rean-nealing treatment under the same annealing condition. In order to achieve more superior magnetic softness of FeCo-based nanocrystalline alloys, the soft magnetic properties of nanocrystalline (Fe 1−x Co x ) 73.5 Si 13.5 B 9 Nb 3 Cu 1 (x=0.25,0.5,0.75) alloys under different magnetic field annealing were investigated.

In some studies, the metal materials with different magnetic permeability and same chemical composition need to be prepared to avoid the interference caused by different compositions and make the parameter of magnetic permeability become the key variable directly. In order to prepare the metal materials with different magnetic and same component, the paper has considered other two commonly schemes, such as the casting method by adding some ferromagnetic elements and the heat-treatment process to increase its phase content of martensite or ferrite. Finally, it has been found that the cold working process was preferable if the austenitic stainless steel 1Cr18Ni9Ti with paramagnetic was selected as a raw material, because it got better control in forging ratio. The method of magnetic balance has been used to measure the relative magnetic permeability of every specimen with different hardness HB 165 (A), HRC 20 (B), HRC 25 (C) and HRC 30 (D). The metallurgical microscope, XRD, TEM and SEM has been put to use to analyse their microstructure before and after forging. The results show, the cold working process improved magnetic properties of 1Cr18Ni9Ti continuously and largely within limits by controlling different forging rate, as well as the process was not complicated. The relative rate of magnetic permeability for 1Cr18Ni9Ti and W18Cr4V (high-speed steel) could be up to 1:2.435 at 0.03 T. The 20.1 % maximum reduction of the austenite phase should be a main reason to improving magnetic permeability of 1Cr18Ni9Ti. The real magneto-crystalline anisotropy should be due to martensite or ferrite phases with strong magnetic property. The 1Cr18Ni9Ti after cold working still maintained high corrosion resistance. Furthermore, this process method was also applicable to other austenitic steels with paramagnetic and strong cold work hardening characteristics.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9696

Partially perpendicular anisotropy in Permalloy thin films was found to produce reliably isotropic permeability in the plane of the film. Isotropic permeability is especially desirable for integrated closed-loop magnetic solenoid inductors in order to create an efficient return path for the flux. Material properties for the Permalloy were verified through hysteresis loop, permeability, and magneto-optic Kerr effect microscopy and utilized to simulate the behavior of the inductor. Laminated Permalloy films with partially perpendicular anisotropy yielded a relatively high permeability value of 860 isotropically in-plane. Simulation results indicate that, depending on the permeability, in-plane closure can yield $2\times $ the inductance or more compared with a rectangular magnetic core with the same permeability. The enhancement due to closure was seen to depend heavily on permeability, increasing at a rate of 6.8 per unit permeability.

Nanocrystalline Fe-based alloys offer a new opportunity for tailoring soft magnetic materials. Nanocrystalline alloy in the form of ribbon with the composition of Fe73.5Cu1Nb3Si13.5B9 was prepared by rapid quenching method for soft magnetic properties analysis. The rapidly quenched alloy has been annealed in a controlled way in the temperature range 490˚C to 680˚C and annealing time 1 min to 60 min. The study of the structural parameters has been investigated by means of XRD analysis. Magnetic properties were analyzed by measuring B-H loop and frequency dependence of initial permeability. Enhanced value of initial permeability by two orders of magnitude and very low value of relative loss factor of the order of 10−3 has been observed with the variation of annealing temperature and time. The initial permeability for the optimum annealed sample has been found 23,064 as compared with 360 for its amorphous counterpart. The initial permeability spectra show dispersion around 100 kHz. Magnetic hysteresis has been investigated by measuring B-H loops at various magnetic fields for different annealing temperature and time. The coercivity and remanence has been found to decrease significantly for optimized annealed condition compared to as-cast state. The core loss of the samples decreases with the annealing time which indicates the good magnetic property of soft magnetic materials.

Development of small, field-portable mass spectrometers has enabled a rapid growth of in-field measurements on mobile platforms. In such in-field measurements, unexpected signal variability has been observed by the authors in portable ion traps with internal electron ionization. The orientation of magnetic fields (such as the Earth's) relative to the ionization electron beam trajectory can significantly alter the electron flux into a quadrupole ion trap, resulting in significant changes in the instrumental sensitivity. Instrument simulations and experiments were performed relative to the earth's magnetic field to assess the importance of (1) nonpoint-source electron sources, (2) vertical versus horizontal electron beam orientation, and (3) secondary magnetic fields created by the instrument itself. Electron lens focus effects were explored by additional simulations, and were paralleled by experiments performed with a mass spectrometer mounted on a rotating platform. Additionally, magnetically permeable metals were used to shield (1) the entire instrument from the Earth's magnetic field, and (2) the electron beam from both the Earth's and instrument's magnetic fields. Both simulation and experimental results suggest the predominant influence on directionally dependent signal variability is the result of the summation of two magnetic vectors. As such, the most effective method for reducing this effect is the shielding of the electron beam from both magnetic vectors, thus improving electron beam alignment and removing any directional dependency. The improved ionizing electron beam alignment also allows for significant improvements in overall instrument sensitivity.

This paper gives an overview on the history and trends of magnetic materials used in electrical machines and motors. The presented materials include silicon–iron, nickel–iron, and cobalt–iron lamination steels, as well as amorphous and nanocrystalline magnetic materials and soft magnetic composites. Development trends and current usage of these selected materials are presented, giving an outlook on the new magnetic material research with regard to electrical machine applications.

AC magnetic properties and core loss behavior of differently prepared Fe-P sheets have been analyzed in this paper. Furthermore, the results have been compared with non-oriented silicon (Si) steel. The coercivity, magnetic flux density, and permeability measurements in dc magnetic field show Fe-P has better soft magnetic properties than Si steel. The ac magnetic behavior of both the samples has been studied in the frequency range from dc to 1 kHz for a range of flux density values. The above studies indicate that crystalline Fe-P alloys can be the replacement of so-called Si steel for low-power device applications.

To enable the realization of weak magnetic field at the level of several nanotesla, a magnetically shielded room (MSR) is required to create a space with residual magnetic field below 1 nT. Since the magnetic field shielded by inner shielding shells is very low, the permeability of shielding materials in this range is measured. As the gaps between ferromagnetic material strips in shielding wall lead to considerable reduction of shielding factor, a new numerical model to evaluate the equivalent permeability of discontinuous shielding layers is proposed and demonstrated experimentally. Based on the equivalent magnetic property in lower and normal magnetic field range, the improved approach to predicting the performance of MSR is obtained.

The influence of magnetic field annealing and Cu content on saturation magnetostriction λ s , effective magnetic anisotropy , and temperature dependence of initial permeability (μ i -T curves) for nanocrystalline Fe 39.4-x Co 40 Nb 2.6 Si 9 B 9 Cu x (x = 0.5, 1, 1.5) alloys was investigated. The λ s and of the alloys were both decreased with Cu content increasing. Magnetic field annealing can obviously reduce λ s , which is due to the rearrangement of random oriented magnetic domain along applied field direction. The increase of is due to the presence of a coherent induced magnetic anisotropy K u under magnetic field annealing, which can be explained in terms of the directional atomic pair ordering theory. In addition, the inverse dependence between μ i and could be changed in the case of magnetic field annealing. In contrast to nonmagnetic field annealing, magnetic field annealing can enhance the room- and high-temperature initial permeability of nanocrystalline Fe 39.4-x Co 40 Nb 2.6 Si 9 B 9 Cu x (x = 0.5, 1, 1.5) alloys; the reason of which was also analyzed.

Effects of compaction and annealing process on the magnetic properties and microstructures of molybdenum permalloy (MP) powder cores have been investigated. MP compacts, with density as high as 92% of the theoretical value, were obtained under 1800 MPa compaction pressure. The MP powder cores show an enhanced effective magnetic permeability of 160 after post-annealing at 690 °C, which is attributed to the relief of internal stress rather than the phase transformation evidenced by the XRD analysis. However, higher annealing temperature destroys the insulating layer, resulting in the drop of the electrical resistivity, the effective magnetic permeability as well as the frequency stability. The results show that the samples compacted at 1800 MPa and annealed at 690 °C exhibit excellent magnetic properties, with core loss of 780 mw/cm 3 (100 kHz, 100 mT) and effective magnetic permeability of 160 whose frequency stability is up to 1 MHz.

In this paper, we focus on preparation and investigation of magnetic and dielectric properties of multicomponent particles with core-shell structure comprising of low-anisotropy MnZn ferrite (core) and polyaniline containing nanoparticles of noble metals (shell). The main advantage of such hybrid magnetic materials is that their electromagnetic properties can be effectively controlled by synthesis conditions. Developed materials can find their potential application as magnetic fillers in the preparation of electromagnetic wave absorbers, where high permeability, high magnetic loss, and optimum ratio between the permeability and permittivity are of high importance.

The effect of magnitude of tensile stresses (σ) applied to the (Fe0.7Co0.3)88Hf2W2Mo2Zr1B4Cu1 alloy with refractory-metal additions during its nanocrystallization at 620°C for 20 min on the magnetic properties, structure, and thermal stability of the alloy is studied. It has been found that, during the nanocrystallization of the alloy under the effect of tensile stresses of 6–250 MPa, longitudinal magnetic anisotropy with an easy magnetization axis parallel to the long size of ribbon is induced in the alloy. The thermal stability of magnetic properties of the alloy under study has been shown to be determined by the thermal stability of induced magnetic anisotropy and to depend on the magnitude of tensile stresses applied during nanocrystallizing annealing (NA). The better thermal stability of magnetic properties has been observed for the alloy subjected to NA at σ = 170 MPa. After annealing at 570°C for 25 h, the magnetic properties of the alloy are unchanged.

Magnetic anisotropy plays an important role in the behavior of a fluxgate core. It is desired to have an anisotropy orthogonal to the direction of the excitation field to move from one saturated state to the opposite saturated state without abrupt change of magnetization. In this paper, we present a method for electroplating a Permalloy film in the shape of a racetrack core with built-in anisotropy. The core is electroplated under bending and later released so that the resulting stress on the film generates the anisotropy. We show how the BH loop of the film changes as we increase the bending radius. Moreover, we demonstrate that electroplating under bending extends the frequency range before the inductance drops. Therefore, the fluxgates based on such cores can be used for higher frequencies (at the expense of lower sensitivity given by lower permeability).

In this study, a simple approach combining nanoporous templates with sputter deposition to obtain nano-sized permalloy structures is presented. The grain evolution and the corresponding magnetic anisotropy of permalloy films grown on the nanoporous anodized aluminum oxide (AAO) substrates with different deposition time were investigated. A grain evolution from a needle-like structure to a 2-D network was observed. As a consequence, the magnetization reversal of the permalloy films varied with the grain evolution. The magnetic domains of the permalloy films were pinned dominantly by the needle-like grain structure at the beginning; then, as the deposition time got longer, the domain sizes were constrained mainly by the underlying AAO network.

The effect of cobalt doping on permeability spectra of nickel ferrites with excess iron ( Ni0.743-xMn0.057CoxFe2.20O4, x=0-0.027) has been studied. With increasing amounts of Co-doping, the static permeability μi decreases at first, then increases to the local maximum at Co substitution of x = 0.018, and finally decreases again. The permeability spectra go through a modification of relaxation-resonance-relaxation dispersions. The samples with Co substitution of x = 0.018 and 0.021 have the static permeability of ~13, resonance frequency of 400 MHz, and sufficiently low magnetic loss tangents, over 1-250 MHz, make them promising candidates for high frequency applications.

Large permeability, low core loss, and high-saturation magnetization are the important parameters for the applications of soft magnetic materials in high-frequency power electronics. By introducing Cr as oxygen-retardant agent in FeHfB melt-spun ribbons and annealing samples in an ultralow partial oxygen pressure environment, we have successfully prevented oxidation of Fe in forming FeCrHfO composites with exchange coupled Fe nanograins. A coercivity of 0.56 Oe and a saturation magnetic flux density of 1.33 T have been achieved in exchange coupled samples. The samples show a high permeability of 250 at 10 MHz.

Electromagnetic Interference (EMI) Shielding material containing a blend of multi walled carbon nano tube (MWCNT) and mumetal has been prepared and their electromagnetic shielding capabilities were characterised through XRD, SEM, EDAX, etc. The shielding effectiveness (SE) was measured using vector network analyser in X-band frequency range (8-12 GHz).

Magnetic cores produced by laminating alternating magnetic/nonmagnetic layers have been shown to eliminate closure domains by linking flux vertically between magnetic layers at the edge of the film. Closure domains, which do not contribute significantly to the permeability, are undesired in patterned magnetic cores for transformers since they reduce the inductance. The inductance of narrow magnetic core transformers was found to drop with increasing frequency. Kerr images of these cores reveal partial closure domains at the edges, which explain the inductance behavior. Edge domain effects are explained based upon energy models of laminated Permalloy strips.

Magnetic and dielectric properties of rubber composites are controlled by using two kinds of high-permeability metal particles with different electrical conductivity (Sendust, Permalloy), and their effect on microwave absorbance has been investigated, focusing on the quasi-microwave frequency band (0.8-2 GHz). Noise absorbing sheets are composite materials of magnetic flake particles of high aspect ratio dispersed in polymer matrix with various filler amount of 80-90 wt.%. The frequency dispersion and magnitude of complex permeability is almost the same for Sendust and Permalloy composite specimens. However, the complex permittivity of the Permalloy composite (, ) is much greater than that of Sendust composite (, ). Due to the large dielectric permittivity of Permalloy composite, the absorbing band is shifted to lower frequency region. However, the investigation of impedance matching reveals that the magnetic permeability is still small to satisfy the zero-reflected condition at the quasi-microwave frequency band, resulting in a small microwave absorbance lower than 10 dB.

The microwave permeability of flake-shaped particles is investigated using a shorted microstrip setup. Several characterizations using two distinct field configurations, with and without the presence of a static field, are performed to provide information about the magnetization dynamics of this new material. A first insight is provided through the framework of Kittel's resonance, but additional features are also found and discussed.

In an integrated power microinductor, the size and shape of the magnetic material will have a relationship to the permeability and inductance of the device. To demonstrate these effects, a set of inductors with closed Ni45Fe55 films were fabricated having similar structures but different footprint sizes and aspect ratios (ARs). Magnetic and electrical characterization was performed on the devices to determine magnetic properties, and in both measurements the same relationship between film shape and magnetic anisotropy is observed. Micromagnetic shape anisotropy simulations were used to predict this behavior and correlate with the experimentally determined parameters. The AR of the film is determined to have a strong influence on the anisotropy and permeability of the magnetic film via shape demagnetization effects which is shown to be a significant variation from the as-deposited magnetic material parameters.

The exchange bias of the soft ferromagnet mu-metal, Ni77Fe14Cu5Mo4, with the metallic antiferromagnet Fe50Mn50 has been studied as a function of ferromagnet thickness and buffer layer material. Mu-metal exhibits classic exchange bias behavior: the exchange bias (HEB) and coercive fields scale inversely with the ferromagnet's thickness, with HEB varying as the cosine of the in-plane applied field angle. While the exchange bias, coercivity, and exchange energy are greatest when the buffer layer material is (111) oriented Cu, amorphous Ta buffers allow the mu-metal to retain more of its soft magnetic character. The ability to preserve soft ferromagnetic behavior in an exchange biased heterostructure may be useful for low field sensing and other device applications., 9 pages, 6 figures

This paper describes a magnetic field powered pressure sensor, which comprises a coil array and a magnetic composite membrane. The composite membrane is made by embedding a ribbon of the amorphous soft magnetic alloy Vitrovac®, in a 17 mm × 25 mm × 1.5 mm Polydimethylsiloxane (PDMS) layer. PDMS is chosen for its low Young's modulus and the amorphous alloy for its high permeability. The membrane is suspended 1.5 mm above a 17×19 array of microfabricated planar coils. The coils are fabricated by patterning a 620 nm thick gold layer. Each coil occupies an area of 36000 μm2 and consists of 14 turns. The sensor is tested by subjecting it to pressure and simultaneously exciting it by a 24 A/m, 100 kHz magnetic field. A pressure change from 0 kPa to 5.1 kPa, results in a 5400 ppm change in the voltage output.

Several applications adopt electromagnetic sensors, that base their principle on the presence of magnets realized with specific magnetic materials that show a rather high remanence, but low coercivity. This work concerns the production, analysis and characterization of hybrid composite materials, with the use of metal powders, which aim to reach those specific properties. In order to obtain the best coercivity and remanence characteristics various "recipes" have been used with different percentages of soft and hard magnetic materials, bonded together by a plastic binder. The goal was to find out the interdependence between the magnetic powder composition and the characteristics of the final material. Soft magnetic material (special Fe powder) has been used to obtain a low coercivity value, while hard materials were primarily used for maintaining a good induction remanence; by increasing the soft proportion a higher magnetic permeability has been also obtained. All the selected materials have been characterized and then tested; in order to verify the validity of the proposed materials two practical tests have been performed. Special magnets have been realized for a comparison with original ones (AlNiCo and ferrite) for two experimental cases: the first is consisting in an encoder realized through a toothed wheel, the second regards the special system used for the electric guitars.

The approach of this research paper is to find out the effect of the temperature on the strength of electricity, magnetism and the electromagnet. Magnets, electromagnets and electricity we are using in our day to day life. And every time these things are dealing with the temperature. This experiment we have conducted to find out that with increase in temperature or with decrease in temperature, will the properties of material (Magnet, Electromagnet and Electricity) will increases or decreases. Or there is chances that their properties value will be constant. To find this, we have used strong magnet made of neodymium, electricity and set of strong electromagnet. Also for cooling the magnet refrigerator and a heating component is used. A wire is used of known resistance. There was lot of change in properties of all these materials after the experimentation.

This study proposes an effective method in the arrangement of layers of high permeability materials for shielding power frequency magnetic field. The side of a neutral ground reactor was blocked with one or two layers of grain-oriented electrical steel (GO), nonoriented electrical steel (NGO), and permalloy (PC). In a weak magnetic field, PC showed the highest shielding performance, whereas GO was the best in a strong magnetic field. NGO had a lower shielding performance than GO, but was better than PC in a very strong magnetic field. When shielding with two layers directly adjacent to each other, the performance level of GO/PC combination (GO is closer to the field source) was between that of GO/GO and PC/PC combinations. When the two layers were slightly separated, on the other hand, GO/PC was most effective in a wide range of magnetic fields. These results are due to the shunt effect of high permeability materials and change of rank of permeability with magnetic field strength between different magnetic materials. Closely adjacent layers act as one body under the regime of shunt mechanism of magnetic shielding. Once the layers are separated, the GO sheet effectively reduces the strong magnetic field first, and then the PC sheet effectively shields the weakened field.

Permalloy is used in a magnetically shielded room to inhibit the penetration of external magnetic field, etc. The flux density in permalloy used in the shielded room is of the order of a few mT or lower. In order to examine the performance of such a shielded room, the dc magnetic properties at low flux density is necessary. In this paper, we developed a measurement method of dc (5 mHz) magnetic properties of permalloy under such a low flux density. It is shown that the dc magnetic properties could be measured more than 4 mT by paying the attention to the degaussing of specimen and applying the correction of drift and offset of measurement system.

Methods of improving functional characteristics of soft magnetic anisotropic materials based on the Fe-3% Si alloy and of amorphous ribbons of the Fe81Si7B12 and Fe81Si4B13C2 alloys have been considered. An efficient method of combined local laser treatment and high-frequency thermomagnetic treatment has been developed. These methods provide an optimization of the magnetic domain structure, a twofold-threefold enhancement of magnetic permeability, a significant reduction of magnetic losses (by 25–30%) and of the coercive force (by 30–40%) of soft magnetic anisotropic materials. A physical method and means for controlling efficiency of the local laser treatment of moving bands of electrotechnical materials have been developed.

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.

In this study, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1-mm-thick metal sheets of mu-metal, grain-oriented electrical steel, and nonoriented electrical steel were prepared from commercial alloy sheets through cold rolling and followed high temperature annealing. For magnetic fields generated by three-phase electric currents, mu-metal was the best in shielding performance when magnetic field at the shield point is about 90 ? T, yielding an excellent shielding factor lower than 0.1 in the vicinity of the shield. Above 490 ? T, however, silicon steels were better than mu-metal. Double-layer shielding with grain-oriented silicon steel (inner) and mu-metal (outer) resulted in an excellent shielding factor up to 490 ?T. These results are due to change in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. For magnetic fields by single-phase electric current, on the other hand, a magnetic shield rather increased magnetic field or had no practical effect on shielding performance. This result is explained by superposition of original field vectors and secondary field vectors created by eddy currents within the materials.

It is shown that the substitution of Co for Fe in the amorphous Fe73.5Cu1Nb3Si13.5B9 alloy leads to the change in the type of magnetic anisotropy induced in the alloy as a result of a thermomechanical treatment at 520°C. The type of the induced magnetic anisotropy determines the functional characteristics of these alloys as soft magnetic materials. With the content of Co in the alloy equal to 10 at % Co, there is induced a magnetic anisotropy with the direction of the easy axis across the ribbon axis (transverse induced magnetic anisotropy), just as in the alloy without Co. Upon the introduction of 20–30 at % Co into the alloy, the induced magnetic anisotropy becomes longitudinal, with the easy-axis direction along the ribbon axis. The thermal stability of the magnetic properties of the alloys with induced magnetic anisotropy has been investigated.