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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.

High magnetic field was introduced to improve the saturation magnetostriction of cast Fe81Ga19 alloy during annealing process. The effects of high magnetic field on the microstructure, magnetic domain structure and magnetostrictive properties were investigated in this paper. Results indicated that high magnetic field could transfer Ga atom from precipitation to parent phase. High magnetic field also enhanced [1 0 0] direction orientation of FeGa alloy. The saturation magnetostriction for Fe81Ga19 alloy annealed at 10 T increased by about five times compared to one without high magnetic field. The improvement in saturation magnetostriction is attributed to the enhanced [1 0 0] orientation and Ga diffusion under high magnetic field during annealing process.

This paper focuses on improving the permeability of Fe-Si-B based amorphous magnetic powder cores by addition of micron-sized ferromagnetic crystalline metal particles (Permalloy). The effects of Permalloy content, size and the amount of insulation on magnetic properties and density were investigated. The results showed that the Fe based amorphous powder cores prepared with 15 wt.% Permalloy (

The structural, magnetic, and transport properties of the Mn2Ni1.8In0.2 alloy have been presented. It was observed to form in tetragonal structure. Multiple magnetic phase transitions have been detected in magnetization data over the temperature range from 2 to 350 K. From the resistivity, ac susceptibility, and heat capacity data, the superconducting transition are observed at T = 5.6 K. The alloy is considered to be one of the potential candidates from the Mn-rich alloys, which has shown both magnetic and superconducting properties, which can be useful from application point of view.

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.

Nanowire/Permalloy (Ni 80 Fe 20 ) composite films were fabricated by combined electrospinning and sputtering. The magnetic properties of the composite films are isotropic in-plane. Stripe domains were characterized by magnetic force microscopy and vector-network-analyzer ferromagnetic resonance. Compared with pure Permalloy films with distinct stripe domains, the composite films have weaker stripe domains but better soft magnetic properties. The coercivity and dynamic anisotropy fields are 47 Oe and 73 Oe, respectively, for pure Permalloy, decreasing to 23 Oe and 67 Oe, respectively, for the Fe-Ni nanowire/Permalloy composite film. Composite films provide new insight on the improvement of the soft magnetic properties of magnetic films.

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.

Contactless current monitoring can play a vital role in electric power distribution side for applications such as power theft control. Operating current can be monitored by contactless magnetic field sensors around the lines. Magnetic flux concentrators (MFCs) are placed to concentrate the magnetic field generated by the current carrying conductor and amplify the magnetic field signals to the magnetic sensors in close vicinity. In this study, three sensors and three MFCs are placed to measure the magnetic field produced by three-phase HV side of the distribution system. Sensors are placed at a distance of 1.2 m from the conductors outside the induction zone. But magnetic fields are weak at this distance. If there is a small change in current through conductors, the resultant magnetic field will also be changed small and at a distance where magnetic fields are already weak, a small change in a magnetic field is difficult for the sensors to be detected. To amplify the weak magnetic field Rectangular shaped Mu metal material base MFCs are designed while the concentration effect can vary by changing the length of MFCs.

Mu-metal shields are widely used in atomic devices, but their magnetic noise related to loss is the key performance limit. The magnetic noise can be calculated by using complex permeability and the magnetic field intensity in the shield. In this study, Bertotti loss separation is used for the first time to accurately calculate the changes of complex permeability due to the hysteresis loss in different frequencies and magnetic field intensities, and we further consider the change in magnetic field intensity due to the induced eddy current, which also increases the accuracy of the magnetic noise calculation. For extremely low frequencies below 20 Hz, the improved noise simulation model differs from the measured results by less than 11%. If the loss separation is not considered, the difference between the measured value and the simulated value would be as high as 54%. The high agreement between the calculation and the experimental results proves the accuracy of the proposed method. Our method can be used in the design and optimization of low-noise magnetic shields to improve the sensitivity of atomic 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.

Behavior of spin waves was investigated in patterned Mu-metal thin film both theoretically and experimentally. The Mu-metal(111) thinfilms with 7 nm thickness were grown by thermal evaporation technique in high vacuum condition. X-ray diffraction measurements showed that the film has a highly FCC crystalline structure. Saturation magnetization and coercive field values of sample obtained from vibrating sample magnetometer are around 500 emu/cm3 and 10 Oe respectively at room temperature. The patterns were square shaped and size of squares were changed between 40–80 µm. Theoretical model and computer program were developed for analyzing the FMR spectra. There is no magnetic anisotropy for in-plane and out-of-plane geometry by both theoretical and experimental investigations. Magnetostatic modes were observed for out-of-plane geometry and these modes were highly compatible with outputs of simulation model.

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.

Near-field noise suppression and conduction losses in a multilayered, amorphous, Co-Zr-Nb thin film with uniaxial anisotropy were simulated and measured with a microstrip line. A 16 dB magnetic near-field shielding effectiveness at 1.1 GHz and a maximum conduction loss around 2.1 GHz were obtained. Eddy-current and ferromagnetic-resonance (FMR) losses were considered as major contributors to near-field noise suppression around 1 GHz. These losses were numerically analyzed by controlling film resistivity and frequency-dependent complex permeability. The degree of shielding effectiveness was significantly controlled by the eddy-current loss. The frequency of the maximum near-field suppression was dominated by the FMR frequency.

In this letter, microwave and magnetostatic measurements of single- and multilayer Permalloy films are made to find physical reasons causing the decrease of the microwave permeability of the films with increase in film thickness. The permeability is measured in the frequency range of 0.1–10 GHz by a coaxial technique. From the measured permeability, a contribution to the effective field from the magnetoelastic effect is determined. The decrease of microwave permeability in thick films is shown to arise mainly due to the perpendicular magnetic anisotropy rather than from the effect of eddy currents, as is frequently suggested. It is also shown that both these effects are reduced in multilayer films comprising alternating magnetic and dielectric layers. Therefore, such films are promising materials for developing magnets that possess high permeability at high frequencies.

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.

The magnetotransport and magnetic properties of Ni 80 Fe 20 , (Ni 80 Fe 20 ) 50 Co 50 and (Ni 80 Fe 20 ) 50 Ag 50 thin films prepared by the thermal evaporation method are presented. Effect of magnetic (Co) and non-magnetic (Ag) elements addition on magnetoresistance, saturation field, coercivity and sensitivity to the magnetic field of permalloy films were described. Structure and magnetic properties of thin film alloys demonstrated a strong dependence from annealing temperature. Also was shown that structure of all types can be used as sensitive elements of magnetic sensors for low magnetic field detecting.

In this work, iron-based soft magnetic composites coated with the amorphous SiO2 layer have been fabricated by utilizing tetraethoxysilane in the reverse microemulsion method, and then the effects of addition amount of SiO2 and annealing temperature on the magnetic properties were investigated. The results show that the surface of iron powders contains a thin amorphous SiO2 insulation layer, which effectively decreases the magnetic loss of synthesized magnets. The magnetic loss of coated samples decreased by 87.8% as compared with that of uncoated samples at 150 kHz. Magnetic measurements show that the sample with 1.25 wt% SiO2 has an acceptable real part and minimum imaginary part of permeability in comparison with other samples. Also, the annealing treatment increased the initial permeability, the maximum permeability and the magnetic induction and decreased the coercivity with increasing temperature in the range 300–600 °C. The results of the loss separation imply that the annealed SMCs have a higher hysteresis loss coefficient (k2) and lower eddy current loss coefficient (k3) as compared with the pure iron compacts after the same heat treatment due to the preservation of the SiO2 layer.

Electrodeposited multilayer-film electromagnetic shields are very promising for protecting various devices due to high shielding efficiency and the possibility of depositing on complex-shaped objects. In this communication, we present the results of measurements of the shielding efficiency of such shields. The shields represent alternating layers of materials with high magnetic permeability (Ni-Fe) and high conductivity (Cu). The maximum number of double layers is 45. It is shown that the shielding efficiency in the weak magnetic fields (0.1–0.2 mT) is 8–10; at higher magnetic field strengths (1.5–2.5 mT), it reaches 80–100. It is shown that the shielding factor increases with the number of layers in the shield at the same thickness of a soft magnetic material. A permalloy shield at the same amount of a soft magnetic material has an efficiency lower by a factor of 3–15 depending on the magnetic field strength.

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.

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.

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.

The amplitude of magnetic permeability and electromagnetic losses are the basis of application of Fe-Ga alloy. Different magnetic hysteresis curves of Fe-Ga alloy are measured using AMH-1M-S dynamic testing system under different conditions, which are the same saturated magnetic field and the same maximum saturation flux density under different frequencies. The complex magnetic permeability, medium energy storage and magnetic losses are analyzed. Electromagnetic loss increases and energy storage of material reduces with increasing of frequency. Hysteresis loss increases linearly with increasing of frequency, the eddy current loss increases dramatically, and the residual loss increases rapidly. The experimental results of this paper can provide guidance for the design of high frequency Fe-Ga ultrasonic transducers.

We present two key results in this work related to magnetic shielding. First, milliscale single layer magnetic shields were fabricated on 3D printed polymer molds and achieved shielding factors in excess of 4500. Second, microscale multilayer shields of alternating 10 μm layers of Permalloy and copper were microfabricated onto silicon using batch fabrication processes and characterized. While conventional electromagnetic interference (EMI) shielding simply requires a conductor for shielding by image charges, dC magnetic shielding requires high permeability material to provide a low reluctance path, redirecting magnetic fields around its volume. Leveraging our expertise in electroplating thick, high permeability (maximum μ r > 8000) Permalloy over sharp topologies, we have demonstrated two processes of producing conformal electroplated shielding. The size, shape flexibility, and shielding factor of these structures enable compact integration of magnetic devices for magnetic microelectronics and atomic, molecular, and optical (AMO) microsystems.