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This work reports the pore‐filling of porous silicon (PSi) and the loading of silicon nanotubes (SiNTs) with Pt‐Fe nanoparticles (NPs) and the corresponding different magnetic behavior of the two composite systems. The fabrication of magnetic hard/soft nanostructures is in demand for the purpose of achieving both a high energy product as well as the replacement of rare earth permanent magnets. Pt‐Fe templated by PSi shows a higher coercivity and remanence than SiNTs/Pt‐Fe and thus a higher hard magnetic performance, the difference between coercivities being about 57%. Considering that the Pt‐Fe deposits employ different molar ratios of Pt to Fe the coercivities vary in a range of 5% in the case of both template types. Comparing Pt‐Fe loaded samples with Co‐loaded samples in all cases, an increase of the coercivity and the remanence is observed for Pt‐Fe, whereas in the case of PSi as template material the increase is significantly stronger (about twice as much) than in the case of SiNTs samples. Furthermore, the samples are investigated at high temperatures up to 950 K to determine the Curie temperature of the systems. [ABSTRACT FROM AUTHOR]

A series of ZnCr2−xHoxSe4 microcrystalline spinels (where x = 0.05, 0.075, and 0.10) containing holmium ions in octahedral coordination were obtained by sintering of adequate reactants at high temperatures. The obtained doped materials were characterized by X-ray diffraction, Scanning Electron Microscopy, UV–Vis–NIR, molecular field approximation, and XPS spectroscopies. Their thermal properties were also investigated. The doping of the ZnCr2S4 matrix with paramagnetic Ho3+ ions with a content of not more than 0.1 and a screened 4f shell revealed a significant effect of orbital and Landau diamagnetism, a strong reduction in short-range ferromagnetic interactions, and a broadening and shift of the peak of the first critical field by simultaneous stabilization of the sharp peak in the second critical field. These results correlate well with FPLO calculations, which show that Cr sites have magnetic moments of 3.19 µB and Ho sites have significantly larger ones with a value of 3.95 µB. Zn has a negligible magnetic polarization of 0.02 µB, and Se induces a polarization of approximately −0.12 µB. [ABSTRACT FROM AUTHOR]

Alkaline-cerium silicate glasses based on the 30CaO-20MgO-5P2O5-45SiO2 (mol%) + CeO2 system were successfully prepared by the melt-quenching route. Cerium dioxide was added as 0.0 g (G1), 0.5 g (G1), 1.5 g (G3), 3 g (G4), and g 5 (G5) over a 100% glass batch. The prepared glasses were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and vibrating-sample magnetometry. The efficiency of the prepared glass as γ-ray protection was evaluated. The amorphous nature of the designed materials was observed for all samples by XRD analysis. The FTIR results confirmed that the bands appearing for G1–G5 represented the main properties of the tetrahedral silicate network SiO4, as silica was the major constituent of the amorphous samples. Values of optical energy band gap (Eg) changed from 3.561 eV to 2.552 eV in the direct transition, while for the indirect transition, the Eg reduced from 3.183 eV to 2.292 eV. The Urbach energy (EU) values ranged from 0.265 eV to 0.205 eV. The refractive index (n) of the investigated glasses improved from 1.253 to 1.572. The energy of the single oscillator (Eo) reduced from 3.988 eV for the G1 sample to 2.915 eV for the G5 sample. The saturation magnetization (Ms) values for the G1, G3, and G5 samples were 0.33414, 0.40572, and 0.49505 emu/g, respectively. The coercivity (Hci) ranged from 36.669 G to 53.321 G, while the remanence magnetization (Mr) ranged from 3.356 to 6.325 (emu/g) E−3. The hysteresis area showed a range of 32.687 to 46.325 (erg/g) at ± 20 kOe. The G5 sample possessed the lowest EBF and EABF values among all investigated glasses. These results validate the suitability of the examined G1–G5 glasses for use in the fields of optical and γ-ray shielding. [ABSTRACT FROM AUTHOR]

Abstract This work reports the pore‐filling of porous silicon (PSi) and the loading of silicon nanotubes (SiNTs) with Pt‐Fe nanoparticles (NPs) and the corresponding different magnetic behavior of the two composite systems. The fabrication of magnetic hard/soft nanostructures is in demand for the purpose of achieving both a high energy product as well as the replacement of rare earth permanent magnets. Pt‐Fe templated by PSi shows a higher coercivity and remanence than SiNTs/Pt‐Fe and thus a higher hard magnetic performance, the difference between coercivities being about 57%. Considering that the Pt‐Fe deposits employ different molar ratios of Pt to Fe the coercivities vary in a range of 5% in the case of both template types. Comparing Pt‐Fe loaded samples with Co‐loaded samples in all cases, an increase of the coercivity and the remanence is observed for Pt‐Fe, whereas in the case of PSi as template material the increase is significantly stronger (about twice as much) than in the case of SiNTs samples. Furthermore, the samples are investigated at high temperatures up to 950 K to determine the Curie temperature of the systems.

With the increasing complexity of power electronics converters, magnetic components like inductors, transformers in different configurations, etc., play important roles in shaping a power controller to meet its desired performance effectively and efficiently. Now, coupled inductors have emerged as one important category of magnetic components that can improve the performance of several types of power controllers used in different domains. They are used to improve the control response, reduce ripple content of output control variables, improve efficiency, enhance power density, etc. This review paper deals with coupled inductors in two ways. Firstly, it details the application prospects as well as design requirements for different applications of coupled inductors. Later, it deals with the design and practical validation of one coupled inductor essentially required for one complex application where the leakage inductance of each winding should be minimal. This review has analyzed that the magnetic circuit design would play a dominant role where both the soft magnetic material and winding layout would be extremely important. While designing a practical coupled inductor, this review article has further analyzed that a core material with low loss density, high saturation flux density and interleaved winding would make the ideal magnetic circuit. The proposed magnetic circuit has been thoroughly validated in a parametric-sensitive power controller for alternating current tungsten inert gas (AC TIG) welding.

This paper deals with the electromagnetic characterization of a laminated toroidal ferromagnetic core made through additive manufacturing, specifically using the laser powder bed fusion process. The continuing demand for increasingly efficient, lightweight, and higher performance electric machines is creating huge challenges in the design and realization of new electric motor solutions. The constant improvements in additive manufacturing technologies have prompted researchers to investigate the possibility of adopting these production techniques for the manufacture of high-value electric motors. For these reasons, this paper investigates the ferromagnetic characteristics of an additively manufactured core made with FeSi6.5 powder. The BH curve and the specific iron losses of the processed material have been measured so that they can be compared with a commercial lamination, and have the possibility of carrying out more precise finite element simulations. [ABSTRACT FROM AUTHOR]

Micromagnets have wide applications in MEMS and micromotors but there are still miniaturization limitations in current microfabrication processes for permanent magnets. A novel damage-free ultrashort pulsed laser machining process to manufacture complex shapes of Sm2Co17 micromagnets is proposed in this work. Laser process permits to further miniaturize the size of the resulting micromagnets achieving very small micromagnets. This can be achieved as micromagnets are submerged in a refrigerant fluid which is especially beneficial for magnets that are materials very sensitive to high temperature. The heat effect of laser cutting on the hard magnetic materials is drastically reduced thanks to the fluid. The detailed description of the manufacturing process is hereby presented. Results of several machining processes like milling and cutting and the magnetic characterization of the resulting micromagnets are shown. Complex segment shapes, with 65-μm thickness made in high-quality Sm2Co17 material, with good accuracy are achieved. It is demonstrated that no permanent degradation of the magnetic properties appears after laser machining. [ABSTRACT FROM AUTHOR]

A series of ZnCr2−xHoxSe4 microcrystalline spinels (where x = 0.05, 0.075, and 0.10) containing holmium ions in octahedral coordination were obtained by sintering of adequate reactants at high temperatures. The obtained doped materials were characterized by X-ray diffraction, Scanning Electron Microscopy, UV–Vis–NIR, molecular field approximation, and XPS spectroscopies. Their thermal properties were also investigated. The doping of the ZnCr2S4 matrix with paramagnetic Ho3+ ions with a content of not more than 0.1 and a screened 4f shell revealed a significant effect of orbital and Landau diamagnetism, a strong reduction in short-range ferromagnetic interactions, and a broadening and shift of the peak of the first critical field by simultaneous stabilization of the sharp peak in the second critical field. These results correlate well with FPLO calculations, which show that Cr sites have magnetic moments of 3.19 µB and Ho sites have significantly larger ones with a value of 3.95 µB. Zn has a negligible magnetic polarization of 0.02 µB, and Se induces a polarization of approximately −0.12 µB.

Ni0.5Co0.5Fe2O4 nanoparticulate powders were synthesized using coprecipitation and sol-gel methods. The crystalline structure of the nanocompounds was determined through X-ray diffraction analysis. The chemical composition of the synthesized nanopowders was analyzed using infrared spectroscopy measurements. The size, morphology, and aggregation of the nanoparticles were determined from electron microscopy images. The magnetic properties of the nanocompounds were studied through magnetization measurements as a function of temperature and applied magnetic field. The synthesized powders consist of aggregates of nanoparticles with mean particle sizes of 24 nm and 43 nm, with those synthesized using the coprecipitation method being smaller. The compounds exhibited a single crystalline phase corresponding to the cubic spinel structure, with a unit cell parameter of approximately 8.35 Å and an inversion parameter with values of 0.94 and 0.95. The synthesized Ni-Co mixed ferrites presented an ordered magnetic behavior below 320 K, with the nanoparticles being in the blocked magnetic regime.

Magnetic separation has wide-ranging applications in both mineral processing and recycling industries. Nevertheless, its conventional utilization often overlooks the interplay between mineral and particle characteristics and their impact on operational conditions, ultimately influencing the efficacy of the separation process. This work describes a methodology able to achieve the comprehensive characterization and classification of Waste Electrical and Electronic Equipment (WEEE) slag. The primary objective is to establish a meaningful connection between the distinct properties of slag phases and their influence on the separation process. Our methodology consists of several stages. Firstly, the WEEE slag is sieved into distinct size classes, followed by classification into magnetic susceptibility classes by using the Frantz Isodynamic separator. To quantify the magnetic susceptibility of each class, we used a magnetic susceptibility balance, and to identify paramagnetic and ferromagnetic fractions and phases within these magnetic susceptibility classes, we conducted vibrating-sample magnetometer measurements. Finally, to establish a meaningful link between the magnetic characterization, mineralogical, and particle-level details, Mineral Liberation Analysis was conducted for each magnetic susceptibility class. This in-depth analysis, encompassing both particle properties and magnetic susceptibility classes, provides a better understanding of the separation behavior of different phases and can help to enrich phases with a specific range of magnetic susceptibility values. This knowledge advances progress towards the development of predictive separation models that are capable of bridging the gap between theoretical understanding and practical application in the field of magnetic separation. [ABSTRACT FROM AUTHOR]

In this study, Bi 0.9 Pb 0.1 Fe 1-x Ti x O 3 (0.05 ≤ x ≤ 0.20) multiferroic ceramics were prepared through solid-state reaction. The influence of Pb, Ti partial substitutions on the dielectric and magnetic properties of BiFeO 3 multiferroic ceramics was investigated and discussed in detail. X-ray diffractions confirm rhombohedral perovskite phase formation (R 3 c space group). Scanning electron microscopy (SEM) was employed to investigate the morphology, revealing a cuboidal microstructure with bimodal distribution of grain sizes. Magnetic studies were carried out and the results reveal a slight enhancement of saturation magnetization with Ti concentration increasing. The present data indicates that Bi 0.9 Pb 0.1 Fe 1-x Ti x O 3 can be used as multifunctional material in different magnetoelectric applications. [ABSTRACT FROM AUTHOR]

Abstract The lack of data is a hindrance to the experimental determination of magnetic cores characteristics. This work presents a non-invasive and field-applicable methodology for electromagnetic devices characterization. Based on fundamental equations of electromagnetism and routine tests, the methodology was applied to obtain, at low frequency: the core loss separation, the hysteresis loop and its BH curve of a three-phase dry core-type transformer. The required equipment and the procedures to do the characterization are presented and discussed. The results were compared with experimental data obtained from tests that were carried out on the same material using a Single Sheet Tester device. The results show a difference in losses of 4.9% for hysteresis, 1.5% for dynamic, and 3.3% for total losses. In the no-load test comparison there was a difference of 4% for dynamics and 1.8% in total losses. The proposed methodology can be applied to different magnetic core types as well as to single-phase transformers and reactors.

Airborne particulate matter is a serious threat to human health, especially in fast-growing cities. In this study, we carried out a magnetic and elemental study on tree leaves used as passive captors and urban dust from various sites in the city of Santiago, Chile, to assess the reliability of magnetic and elemental measurements to characterize particulate matter pollution from vehicular origin. We found that the magnetic susceptibility and saturation isothermal remanent magnetization measured on urban tree leaves is a good proxy for tracing anthropogenic metallic particles and allow controlling the exposure time for particulate matter collection, in agreement with other studies carried out in large cities. Similar measurements on urban soil can be influenced by particles of detritic (natural) origin, and therefore, magnetic measurements on tree leaves can help to identify hotspots where fine particles are more abundant. Elemental particle-induced X-ray emission analysis of tree leaves showed the presence of a number of elements associated with vehicular emissions, in particular Cu, Zn, Fe, K and S which are present at every site, and As, Se, V, Ni, Sr, Zr, Mo and Pb identified at some sites. We observed a correlation between magnetic parameters and the concentrations of S and Br as well as Cu to a smaller extent. Moreover, this study shows the importance of selecting carefully the tree species as well as the location of trees in order to optimize phytoremediation. [ABSTRACT FROM AUTHOR]

The lack of data is a hindrance to the experimental determination of magnetic cores characteristics. This work presents a non-invasive and field-applicable methodology for electromagnetic devices characterization. Based on fundamental equations of electromagnetism and routine tests, the methodology was applied to obtain, at low frequency: the core loss separation, the hysteresis loop and its BH curve of a three-phase dry core-type transformer. The required equipment and the procedures to do the characterization are presented and discussed. The results were compared with experimental data obtained from tests that were carried out on the same material using a Single Sheet Tester device. The results show a difference in losses of 4.9% for hysteresis, 1.5% for dynamic, and 3.3% for total losses. In the no-load test comparison there was a difference of 4% for dynamics and 1.8% in total losses. The proposed methodology can be applied to different magnetic core types as well as to single-phase transformers and reactors. [ABSTRACT FROM AUTHOR]

Solid-state wafers are indispensable components in material science as substrates for epitaxial homo- or heterostructures or carriers for two-dimensional materials. However, reliable determination of magnetic properties of nanomaterials in volume magnetometry is frequently affected by unexpectedly rich magnetism of these substrates, including significant magnetic anisotropy. Here, we describe a simplified experimental routine of magnetic anisotropy assessment, which we exemplify and validate for epi-ready sapphire wafers from various sources. Both the strength and the sign of magnetic anisotropy are obtained from carefully designed temperature-dependent measurements, which mitigate all known pitfalls of volume SQUID magnetometry and are substantially faster than traditional approaches. Our measurements indicate that in all the samples, two types of net paramagnetic contributions coexist with diamagnetism. The first one can be as strong as 10% of the base diamagnetism of sapphire [−3.7(1) × 10−7 emu/gOe], and when exceeds 2%, it exhibits pronounced magnetic anisotropy, with the easy axis oriented perpendicularly to the face of c-plane wafers. The other is much weaker, but exhibits a ferromagnetic-like appearance. These findings form an important message that nonstandard magnetism of common substrates can significantly influence the results of precise magnetometry of nanoscale materials and that its existence must be taken for granted by both industry and academia. [ABSTRACT FROM AUTHOR]

Magnetic separation has wide-ranging applications in both mineral processing and recycling industries. Nevertheless, its conventional utilization often overlooks the interplay between mineral and particle characteristics and their impact on operational conditions, ultimately influencing the efficacy of the separation process. This work describes a methodology able to achieve the comprehensive characterization and classification of Waste Electrical and Electronic Equipment (WEEE) slag. The primary objective is to establish a meaningful connection between the distinct properties of slag phases and their influence on the separation process. Our methodology consists of several stages. Firstly, the WEEE slag is sieved into distinct size classes, followed by classification into magnetic susceptibility classes by using the Frantz Isodynamic separator. To quantify the magnetic susceptibility of each class, we used a magnetic susceptibility balance, and to identify paramagnetic and ferromagnetic fractions and phases within these magnetic susceptibility classes, we conducted vibrating-sample magnetometer measurements. Finally, to establish a meaningful link between the magnetic characterization, mineralogical, and particle-level details, Mineral Liberation Analysis was conducted for each magnetic susceptibility class. This in-depth analysis, encompassing both particle properties and magnetic susceptibility classes, provides a better understanding of the separation behavior of different phases and can help to enrich phases with a specific range of magnetic susceptibility values. This knowledge advances progress towards the development of predictive separation models that are capable of bridging the gap between theoretical understanding and practical application in the field of magnetic separation.

In space magnetic exploration missions, the measurements obtained from the magnetic sensors mounted on a spacecraft are often influenced by the spacecraft's own magnetic interference. Therefore, to ensure precise magnetic exploration, it is imperative to conduct a thorough magnetic characterization of the spacecraft. Conducting the magnetic characterization of spacecraft within a magnetic shielded room (MSR) can mitigate the influence of environmental noise on the characterization process, thereby minimizing uncertainty and enhancing modeling accuracy. However, the utilization of high-permeability materials (such as permalloy) in the MSR introduces a disparity in magnetic characteristics between the spacecraft inside and outside the MSR. According to the method of images, the magnetic field generated by the spacecraft inside the MSR is the superposition of the magnetic fields produced by the spacecraft and that produced by several images of itself. Therefore, this may lead to an ambiguity problem, where spacecrafts with different magnetic characteristics and their corresponding images can generate identical magnetic field distribution in the MSR. To address the aforementioned issues, this paper proposes a novel method for magnetic characterization that integrates both the magnetic field vector data within the MSR and the magnetic field gradient data outside the MSR generated by the spacecraft, allowing for the elimination of the ambiguity problem without introducing environmental magnetic noise interference. As a result, it obtains a unique model for precisely representing the spacecraft's magnetic characteristics in terms of the spherical harmonic coefficients. [ABSTRACT FROM AUTHOR]

In electrical machines, laminated steels are commonly adopted as soft magnetic materials, while for permanent magnets, sintered ferrites and NdFeB are the most common solutions. On the other hand, the growing demand for volume reduction with the increment of efficiency leads to the necessity of exploring other magnetic materials able to face the challenge better than the traditional ones. Bonded magnets have been used to replace sintered magnets, obtaining a better use of space and particular magnetic properties. Instead, for the magnetic circuit, Soft Magnetic Composites (SMC) allow realizing very complex magnetic design (3D path for flux) with iron loss reduction at medium-high frequencies, especially for the eddy currents loss contribution. On the other hand, SMC materials have such drawbacks as low mechanical properties and high hysteresis losses. For this reason, in this work, different studies considering several variables have been carried out. SMCs were produced through a moulding process; inorganic and organic layers to cover ferromagnetic particles were used, adopting different coating processes. Particular tests have been performed for a quicker and more indicative overview of the materials obtained. The single sheet tester (SST) is easier than traditional toroidal methods; on the other hand, the multiplicity of variables affects the SMC materials and their process. For this reason, coercivity and conductibility tests permit rapid measurement and provide a direct classification of the produced SMCs, providing the main information needed to select suitable materials. Results highlighted that choosing the more appropriate SMC material is possible after using these simple preliminary tests. After these tests, it was possible to argue that with 0.2 wt% of phenolic resin as the organic layer (and compaction pressure of 800 MPa), it is possible to produce a good SMC. On the other hand, the SMC with 0.2 wt% of epoxy resin (and compaction pressure of 800 MPa) gives a minor coercivity value. Additionally, despite the SMC with the inorganic layer, 0.2 wt% of nano-ferrites showing the best coercivity values (specifically for vacuum treatment at 600 °C), their resistivity was unsatisfactory. [ABSTRACT FROM AUTHOR]

In this article, an experimental procedure is presented to handle magnetic measurements under uniaxial tensile stress reaching the plastic domain. The main advantage of the proposed procedure is that it does not require an additional magnetic core to close the magnetic flux path through the studied sample. The flux flows only in the sample, and no parasitic air gaps are introduced, thus avoiding the use of the H-coil to evaluate the magnetic field, which is often very sensitive and not easy to calibrate. A specimen of nonoriented FeSi (1.3%) sheet (M330-35A) is characterized under uniaxial tensile stress. To validate the proposed procedure, a comparison with the single sheet tester procedure is carried out. The results obtained by the two procedures are in good agreement. Moreover, to illustrate the possibilities offered by the proposed procedure, we confirm some results obtained in the literature. We show that the positive plastic strain leads to a significant degradation of magnetic behavior. An applied tensile stress on a virgin (unstrained) sample leads to a degradation of the magnetic behavior. However, on a pre-strained sample, an applied tensile stress results in reducing the deterioration caused by the plastic strain until a stress value called optimum is attained. Above this threshold, the magnetic behavior re-deteriorates progressively.

We have developed a vector network analyzer ferromagnetic resonance (VNA‐FMR) spectrometer with field modulation detection. This system provides broadband coverage and very high sensitivity to resolve the FMR signal on a ultra‐thin (∼ 1 nm thick) magnetic film. This paper first presents the detail of the VNA‐FMR spectrometer built in this work, including its operation principle and design guideline, and second various magnetic properties obtained by the VNA‐FMR measurement results. [ABSTRACT FROM AUTHOR]

During electrical machine manufacturing, the process may induce plastic mechanical strains, especially in the magnetic core. However, magnetic properties are highly sensitive to the material mechanical state. Thus, the performances of electrical machines, which also rely on the magnetic material properties, are often deteriorated. This article proposes an approach to reduce the impact of the forming process on the magnetic core performances by creating high localized heterogeneous deformations instead of having a low homogeneous deformation distributed on the whole structure. A NO (non-oriented) FeSi (1.3%) electrical steel (M330-35A) is characterized after uniaxial tensile test. Samples are deformed either in heterogeneous or in homogeneous ways while keeping the same global deformation. Experimental measurements show that, for the same displacement value, the heterogeneous configuration, with localized strain, deteriorates less the global magnetic properties than the homogeneous configuration. These results are supported by a magneto-mechanical modeling approach that predicts accurately the physical behavior of the test samples. [ABSTRACT FROM AUTHOR]

Solid-state wafers are indispensable components in material science as substrates for epitaxial homo- or heterostructures or carriers for two-dimensional materials. However, reliable determination of magnetic properties of nanomaterials in volume magnetometry is frequently affected by unexpectedly rich magnetism of these substrates, including significant magnetic anisotropy. Here, we describe a simplified experimental routine of magnetic anisotropy assessment, which we exemplify and validate for epi-ready sapphire wafers from various sources. Both the strength and the sign of magnetic anisotropy are obtained from carefully designed temperature-dependent measurements, which mitigate all known pitfalls of volume SQUID magnetometry and are substantially faster than traditional approaches. Our measurements indicate that in all the samples, two types of net paramagnetic contributions coexist with diamagnetism. The first one can be as strong as 10% of the base diamagnetism of sapphire [−3.7(1) × 10−7 emu/gOe], and when exceeds 2%, it exhibits pronounced magnetic anisotropy, with the easy axis oriented perpendicularly to the face of c-plane wafers. The other is much weaker, but exhibits a ferromagnetic-like appearance. These findings form an important message that nonstandard magnetism of common substrates can significantly influence the results of precise magnetometry of nanoscale materials and that its existence must be taken for granted by both industry and academia.

Accurate and early estimation of the thermal stability factor of a memory array is essential for the development of modern non-volatile magnetic storage devices. We propose an evaluation method for effective array-level thermal stability factors (Δeff) via magnetic characterization of patterned magnetic tunnel junction (MTJ) arrays. These patterned arrays do not require traditional electrical contacts and circuitry that are usually needed for Δeff evaluation. Using vibrating sample magnetometer (VSM) at elevated temperatures and under applied fields, we demonstrate that these MTJ arrays exhibit a moment change trend that fits the Néel–Brown model and are able to extract the respective Δeff. The domain-wall-mediated reversal model is used to obtain zero-field Δeff. Using this method, we have optimized MTJ film stacks based on fast array-level feedback and validated high data retention of Δeff ~ 46 at 260 °C from fully integrated MTJ bit arrays. [ABSTRACT FROM AUTHOR]

In electrical machines, laminated steels are commonly adopted as soft magnetic materials, while for permanent magnets, sintered ferrites and NdFeB are the most common solutions. On the other hand, the growing demand for volume reduction with the increment of efficiency leads to the necessity of exploring other magnetic materials able to face the challenge better than the traditional ones. Bonded magnets have been used to replace sintered magnets, obtaining a better use of space and particular magnetic properties. Instead, for the magnetic circuit, Soft Magnetic Composites (SMC) allow realizing very complex magnetic design (3D path for flux) with iron loss reduction at medium-high frequencies, especially for the eddy currents loss contribution. On the other hand, SMC materials have such drawbacks as low mechanical properties and high hysteresis losses. For this reason, in this work, different studies considering several variables have been carried out. SMCs were produced through a moulding process; inorganic and organic layers to cover ferromagnetic particles were used, adopting different coating processes. Particular tests have been performed for a quicker and more indicative overview of the materials obtained. The single sheet tester (SST) is easier than traditional toroidal methods; on the other hand, the multiplicity of variables affects the SMC materials and their process. For this reason, coercivity and conductibility tests permit rapid measurement and provide a direct classification of the produced SMCs, providing the main information needed to select suitable materials. Results highlighted that choosing the more appropriate SMC material is possible after using these simple preliminary tests. After these tests, it was possible to argue that with 0.2 wt% of phenolic resin as the organic layer (and compaction pressure of 800 MPa), it is possible to produce a good SMC. On the other hand, the SMC with 0.2 wt% of epoxy resin (and compaction pressure of 800 MPa) gives a minor coercivity value. Additionally, despite the SMC with the inorganic layer, 0.2 wt% of nano-ferrites showing the best coercivity values (specifically for vacuum treatment at 600 °C), their resistivity was unsatisfactory.

Nickel/nickel oxide-carbon magnetic fibers were prepared by Solution Blow Spinning (SBS) of polyvinyl alcohol (PVA) and Ni-nitrate. As-spun fibers with relative Ni nitrate/PVA concentrations of 30 wt% and 60 wt% were calcined at 550 °C in argon flux. The samples characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and DC magnetic measurements. TEM images show a carbon matrix containing sphere-like nanoparticles with diameters in the range of 4–45 nm. The magnetic assessment shows the presence of superparamagnetic small particles with blocking temperatures between 14 and 22 K, and large particles that are thermally blocked at 300 K. The low magnetization signal, with saturation magnetization in the range of 7–10 emu/g, is due to dead magnetic layers at the surface of nanoparticles. • Solution blow spun nickel-nickel oxide/carbon composite fibers. • Effect of the Ni nitrate/PVA concentration on the magnetic properties and particle size. • Superparamagnetic signal with blocking temperatures between 14 and 22 K. [ABSTRACT FROM AUTHOR]

Materials with spinel structures have the general stoichiometric formula AB 2 O 4. Their constituent elements A and B determine specific properties, some of important technological interest, particularly related to magnetic behavior. In the present study Aluminum–Iron, single-phase spinel, rarely found in nature, has been synthesized via combustion reaction. The presence and amount of urea as combustion source has been varied in order to verify its influence on the microstructure and magnetic properties of the product material. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the synthesized powders. The microstructural analysis indicated that the sample synthesized without urea as fuel corresponds to iron and aluminum oxides, but mostly amorphous, with low intensity X-ray diffraction peaks corresponding to Hematite particles. The samples produced with urea displayed in their X-ray diffractogram well defined peaks allowing to index the crystallographic planes of the constitutive phases: spinel and magnetite. Among these, the sample synthesized with stoichiometric amount of urea indicate being constituted by single-phase FeAl 2 O 4 spinel. However, the samples synthesized with excess and deficiency of urea showed, besides the production of the desired spinel, the formation of Fe 3 O 4 have occurred. Magnetic measurements indicate that samples synthesized with urea behave as a ferromagnetic material, while samples produced without urea exhibits paramagnetic behavior. [ABSTRACT FROM AUTHOR]

We report the microscopic, magnetic and rheological properties of magnetorheological elastomers (MRE) with carbonyl iron magnetic particles (CIP) dispersed into silicone in the concentration range 5–30% volume content. The samples have been fabricated under the action of a magnetic field (anisotropic A-MRE) or without it (isotropic I-MRE). For the A-MRE samples and at low particle concentration, the anisotropy is evident in the microstructure and the magnetic properties. However and at high particle concentration, the microstructural and magnetic anisotropy is much less noticeable and makes difficult to distinguish between isotropic and anisotropic state. The rheological characterization shows changes in the storage modulus G′ when CIP content is from 5 to 30% volume and I-MRE (72% change) and A-MRE (70% change) character of the samples. However, this influence is remarkable in the loss modulus G″ with big changes when considering CIP content from 5 to 30% volume and I-MRE (114% change) and A-MRE (142% change). We have also determined that the anisotropic samples with high particle content present the maximum magnetorheological effect of about 31% at low frequency (1–2 Hz). [ABSTRACT FROM AUTHOR]

In this article, the energy balance equation in the original Jiles–Atherton model is revisited. In particular, the assumption that the energy stored in a lossy material is equal to that stored in a lossless material is removed. This modification results in more accurate prediction of $B$ – $H$ trajectories. A new approach to characterize material parameters based on resonant response is also set forth. Extensive experimental validation is provided and model parameters for several common materials are given. [ABSTRACT FROM AUTHOR]

In the present work, the α-Fe2O3/RGO nanocomposite is synthesized by one-pot solvothermal technique. The structural analysis is accomplished using X-ray diffraction and Raman spectroscopy. Temperature and field-dependent magnetic investigation of α-Fe2O3/RGO nanocomposite has been carried out from 350 to 10 K. The transition of magnetic states in α-Fe2O3/RGO hybrid with changing temperature is discussed based on average anisotropy energy and coupling interactions. The ZFC-FC curves are also analyzed to explore the system further. [ABSTRACT FROM AUTHOR]

Indoor localization using magnetic and inertial sensors has shown its effectiveness due to the pervasiveness of magnetic fields and independence from external infrastructure. However, when massive crowdsourced data are obtained in mass-market applications, new issues occur and degrade the magnetic matching (MM) performance. To alleviate these issues, an orientation-aided stochastic MM method is presented. First, orientation-aided magnetic fingerprints are applied to effectively improve fingerprint fidelity when massive data are used. Second, this paper characterizes crowdsourced magnetic fingerprints and reveals that the stochastic magnetic components may have different histograms, such as the symmetric, left-skewed, bimodal, and irregular ones. Based on such outcome, Gaussian distribution and histogram model based stochastic MM methods are presented to mitigate the degradation from stochastic magnetic components, which have not been involved in the existing MM methods such as nearest neighbor and dynamic time warping. Compared to the deterministic MM methods, this research provides a deeper insight into the use of magnetic fingerprints and more accurate MM and MM/dead-reckoning integrated localization solutions. [ABSTRACT FROM AUTHOR]

Core-shell and multilayered nanoparticles based on magnetite core with different metallic spacing and over-layers are prepared in one pot synthesis and characterized. The spacer layers were made from Au, Cu or Ag precursors. The nanoparticles were fabricated by a modified chemical seed based method. The obtained nanoparticles were examined by X-ray diffraction, Energy-dispersive X-ray spectroscopy, Transmission Electron Microscopy, Differential Scanning Calorimetry and Infrared spectroscopy. Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy and Magnetometry. Magnetization and Mössbauer measurements show that the presence of the metallic layers influences the magnetic state of the particles. XRD and EDX confirm layered structures of nanoparticles. Proposed synthesis allows for fabrication of layered particles with controlled morphology and register properties changes which are related to the nature of each subsequent layer. [ABSTRACT FROM AUTHOR]

Polycrystalline Bi2Fe4O9 nanoparticles were successfully prepared by a hydrothermal assisted sol-gel method. X-ray diffraction (XRD) data, Fourier transform infrared (FTIR) spectra, and Raman spectra reveal that Bi2Fe4O9 nanoparticles has orthorhombic mullite structure without other impurities such as Bi2O3, Fe3O4, BiFeO3, Fe2O3. Scanning electron microscopy (SEM) shows that the synthesized polycrystalline Bi2Fe4O9 particles have regular spherical shape and the average particle size of 50 nm. Optical properties of the Bi2Fe4O9 nanoparticles were studied by UV–Vis absorption spectroscopy, and the bandgap energy (Eg) value is found to be 1.75 eV. Magnetic characterization shows that the Bi2Fe4O9 nanoparticles exhibit a paramagnetic behavior at 300 K and undergo an antiferromagnetic transition at 190 K. Ferroelectric hysteresis loops with rounded corners at room temperature at 50 Hz are observed for the Bi2Fe4O9 nanoparticles due to the large electrical leakage. Photocatalytic experiments indicate that the Bi2Fe4O9 nanoparticles exhibit excellent photocatalytic activity and stability in degradation of methylene blue (MB) and methyl red (MR) dyes under visible light irradiation. [ABSTRACT FROM AUTHOR]

An experimental approach is proposed to study the influence of the punching on the magnetic behavior of a stator core strips. Specimens of a non-oriented M330-A35 punched lamination sheet are picked up from a real manufacturing process. The proposed approach is based on the use of two types of specimens; one is a closed magnetic circuit while the second one is split into two parts. Magnetic measurements are performed on both types and compared with those made on specimens cut by WEDM which has a lower impact on the magnetic behavior. The specific purpose of this paper is to investigate the impact of punching in presence of an air gap that exists in electrical machines between rotor and stator. Therefore a dedicated device, optimized by FEM simulations, is developed in order to account accurately the air gap. [ABSTRACT FROM AUTHOR]

Pyrite and greigite were identified in the wood of two ancient shipwrecks using an original multi-technique analytical approach. Structural characterization methods such as environmental scanning electron microscopy, micro-Raman spectroscopy and X-ray diffraction were combined with magnetic measurement methods, such as magnetic susceptibility measurements and isothermal remanent magnetization acquisition curves. This is the first time that magnetic measurement methods are used in the field of cultural heritage to study wet organic archaeological materials. They proved to be particularly suitable to detect with a very high sensitivity ferromagnetic s.l. mineral phases inside waterlogged wooden samples, i.e. in the bulk. The occurrence of iron sulfides in archaeological shipwrecks extracted from waterlogged environments is usually attributed to microbiologically influenced corrosion of iron fasteners. This study demonstrates that the nature of the identified iron sulfides is consistent with a step-by-step in situ anoxic oxidation process of mackinawite. • Waterlogged wood-iron assemblies are affected by iron fasteners corrosion influenced by sulfides • Greigite an pyrite were detected in the wood of two ancient archaeological shipwrecks through an original methodological approach • Greigite was characterized by magnetic measurements methods • The nature of iron sulfides present in archaeological shipwrecks is related to the duration of the burial in anoxic conditions and of the exposure to sulfides • Waterlogged archaeological wood-iron assemblies testify of the iron sulfides evolution from the precursor corrosion product mackinawite. [ABSTRACT FROM AUTHOR]

Flexible radar-absorbing materials have great application significance in stealth technology. In this paper, a novel radar-absorbing material based on ferromagnetic nickel micron-fibers with 38–40 mm length and 10–12 µm diameter was successfully prepared through bundle-fiber drawing and electrochemical treatment. The characterization of morphology, chemical composition, magnetic and mechanical properties, including tensile strength, bending rigidity and friction, of the prepared ferromagnetic nickel micron-fiber is investigated. The results showed that compared with conventional radar absorbers, ferromagnetic nickel micron-fibers have many advantages in their appearance and magnetic performance. The total ferromagnetic metal fraction of Ni and Fe was above 90%. Irregular cross-section and large aspect ratio of 3800 of the fiber enabled the magnetic hysteresis loss and absorbing performance to be increased obviously. Its saturation magnetization Ms was 116 emu/g with coercivity Hc of 5.8 × 103A/m, initial permeability of 2036 H/m and Curie temperature of 996 K, confirming the fiber performed a relatively strong magnetic absorbing effect and high temperature stability. The tensile and friction properties of ferromagnetic nickel micron-fiber were also analyzed to evaluate the spinnability. [ABSTRACT FROM AUTHOR]

Abstract The Loncopué Trough is a Pliocene to Quaternary extensional basin developed over the hinterland area of the Southern Central Andes. This basin is bounded by two neotectonic extensional fault systems delimiting a narrow topographic low. Previous studies have mostly focused on structural and geochemical aspects of this feature. However, geophysical surveys, aimed to unravel deep structure beneath a thick-younger than 5 My volcanic coverage, are scarce and based their interpretations on low resolution data sets. In this study, we collected new aeromagnetic data with the objective of characterizing the magnetic properties of the crust in the Loncopué Through and nearby zones. Additionally, we analyze the spatial relation between geological structures, volcanic fields and magnetic data. In order to highlight the boundaries of the magnetic sources and calculate the basement depth, we applied derivative techniques and the source parameter imaging. Also, we estimated an effective susceptibility model using the Magnetization Vector Inversion method, which takes into account the combined effects of remanence and induced magnetization. To determine the thermal structure of the area, we calculated the Curie depth points through the spectral analysis technique. From the analysis of magnetic data we were able to characterize the main structures and lineaments associated with this retroarc extensional trough. Notably, only the Loncopué eastern fault system seems to be a crustal-scale tectonic feature, while E-W-, ENE- and ESE-trending lineaments are interpreted as relatively minor structures segmenting the basement. Finally, our susceptibility model, together with the analysis of the Curie point, revealed potential magmatic/hydrothermal reservoirs in the Copahue volcano, and the Codihue and Cajón de Almanza regions that could be connected at depth forming a regional magmatic body. Highlights • We study the Loncopué trough a Pliocene to Quaternary extensional basin. • We analyze aeromagnetic data and we apply different processing tech-niques. • We calculate an effective susceptibility model by an inversion method. • The results show the existence of previously unknown magmatic/hydrothermal reservoirs. • This is compatible with slab tearing hypotheses and plume upwelling. [ABSTRACT FROM AUTHOR]

The MnAl ferromagnetic phase has great potential for industrial applications as one of a family of non-rare-earth permanent magnets due to its large magnetocrystalline anisotropy, high magnetization, high Curie temperature, low cost, and relatively easy processing. This research exploited an induction casting furnace protected by an Ar atmosphere to prepare the τ-MnAl magnetic phase. Considering the appropriate compositions, pure (Mn54Al46, known as MnAl), 2 wt. % (MnAl98-Cu2), and 5 wt. % (MnAl95-Cu5) Cu-added MnAl samples were alloyed. The microhardness and bulk density of the melted ingots increased from pure to 2 wt. % Cu alloys accompanied by a slight decrease in 5 wt. % Cu-added sample. XRD and SEM confirmed the formation of the τ, γ, and β phases in all three sets of initially melted ingots. At the same time, it was revealed that the addition of Cu could facilitate the formation of the ferromagnetic τ-MnAl phase in both doped samples. The research results showed that adding copper stabilizes the τ phase directly and affects the magnetic properties of the MnAl samples, resulting in an increase in the coercivity and remanence. The HC of the Mn54Al46 and the five percent-copper-added samples changed from 250 to 500 Oe, respectively. While the saturation magnetization remained nearly unchanged, the remanence showed an uptrend and increased remarkably from 5.40 emu/g (pure) to 11.62 emu/g (for 5 wt. % Cu). The results of this study show that adding Cu could be beneficial in promoting the magnetic properties of pure MnAl. However, more systematic studies are needed to adjust the proper amount of Cu, especially for final heat-treated samples. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles combine unique magnetic properties that can be used in a variety of biomedical applications for therapy and diagnostics. These applications place high demands on the magnetic properties of nanoparticles. Thus, research, development, and quality assurance of magnetic nanoparticles requires powerful analytical methods that are capable of detecting relevant structural and, above all, magnetic parameters. By directly coupling nanoparticle synthesis with magnetic detectors, relevant nanoparticle properties can be obtained and evaluated, and adjustments can be made to the manufacturing process in real time. This work presents a sensitive and fast magnetic detector for online characterization of magnetic nanoparticles during their continuous micromixer synthesis. The detector is based on the measurement of the nonlinear dynamic magnetic response of magnetic nanoparticles exposed to an oscillating excitation at a frequency of 25 kHz, a technique also known as magnetic particle spectroscopy. Our results underline the excellent suitability of the developed magnetic online detection for coupling with magnetic nanoparticle synthesis based on the micromixer approach. The proven practicability and reliability of the detector for process monitoring forms the basis for further application fields, e.g., as a monitoring tool for chromatographic separation processes.

We present the evolution of magnetic anisotropy obtained from the magnetization curve of (Fe0.76Si0.09B0.10P0.05)97.5Nb2.0Cu0.5 amorphous and nanocrystalline alloy produced by a gas atomization process. The material obtained by this process is a powder exhibiting amorphous character in the as-atomized state. Heat treatment at 480 °C provokes structural relaxation, while annealing the powder at 530 °C for 30 and 60 min develops a fine nanocrystalline structure. Magnetic anisotropy distribution is explained by considering dipolar effects and the modified random anisotropy model.

Polymer bonded permanent magnets find significant applications in a multitude of electrical and electronic devices. In this study, magnetic particle-loaded epoxy resin formulations were developed for in-situ polymerization and material jetting based additive manufacturing processes. Fundamental material and process issues like particle settling at room temperature and elevated temperature curing, rheology control and geometric stability of the magnetic polymer during the thermal curing process are addressed. Control of particle settling, modifications in rheological behavior and geometric stability were accomplished using an additive that enabled the modification of the formulation behavior at different process conditions. The magnetic particle size and additive loading were found to influence the rheological properties significantly. The synergistic effect of the additive enabled the developing of composites with engineered magnetic filler loading. Morphological characterization using scanning electron microscopy revealed a homogenous particle distribution in composites. It was observed that the influence of temperature was profound on the coercive field and remanent magnetization of the magnetic composites. The characterization of magnetic polymers and composites using rheometry, scanning electron microscopy, X-ray diffraction and superconducting quantum interference device (SQUID) magnetometry analysis enabled the correlating of the behavior observed in different stages of the manufacturing processes. Furthermore, this fundamental research facilitates a pathway to construct robust materials and processes to develop magnetic composites with engineered properties.

The interest around the adoption of Soft Magnetic Composite materials (SMC) in the realization of electric machines, or parts of electric machines, is continuously increasing. The main reason lies on the opportunity to realize magnetic circuits following a 3D design procedure, which is not allowed with the adoption of the traditional lamination sheets. This is not the only reason, as a lot of research is being carried out on the losses distribution in the magnetic material, particularly as function of the frequency. In this paper different iron powders have been analyzed to investigate the impact of the granulometry on the SMC performance; in particular the grain size and the oxygen content have been considered variable parameters. The materials, prepared, compacted and tested in our laboratories, have been characterized to obtain the magnetic characteristic and information about the iron losses.

Co 1-x Zn x Fe 2 O 4 (0.08 ≤ x ≤ 0.56) powders prepared by a sol-gel auto-combustion method have been investigated through the combined use of structural and dc/ac-magnetization measurements under a wide range of applied magnetic field values. EDS spectra are performed to evaluate the samples chemical composition, whereas the X-ray diffraction measurements indicate the formation of the typical nanocrystalline mixed cubic spinel structure and allow to determine the cationic distribution as well as the lattice parameter and the oxygen position as function of Zn content. Magnetic characterization improves the knowledge about the correlation between the structural properties and magnetic behavior. The magnetization curves show a hysteretic behavior at room temperature and they are analyzed as function of Zn content taking in account the Yafet-Kittel’s model. The replacement of non-zero magnetic moment Co 2+ ions with zero magnetic moment Zn 2+ ions induces a gradual reduction of magnetocrystalline anisotropy and a lowering of the magnetic coercivity. The energy lost in a static and alternating magnetic field (frequency of 69 kHz) at selected vertex field values for the studied samples has been calculated in order to evaluate their prospective usage to operate in different field conditions. [ABSTRACT FROM AUTHOR]