Amorphous Soft Magnetic Materials Research Articles

Highly sensitive surface acoustic wave magnetic field sensor based on the loss mechanism

Currently, the surface acoustic wave (SAW) magnetic field sensing technique utilises the SAW velocity/frequency mechanism of magnetoacoustic interaction as an indicator of the magnetic sensitivity mechanism. However, this method has low sensitivity and poor stability. To address this problem, a dynamic magnetoelastic coupling theoretical model is constructed to theoretically simulate the influence of the ΔE effect of magnetically sensitive thin films on SAW propagation attenuation. This study describes a high-sensitivity SAW magnetic field sensing mechanism based on magnetoacoustic attenuation. The simulation results show a clear relationship between the acoustic propagation loss and external magnetic field, indicating a structure-property relationship. An amorphous soft magnetic material (Fe90Co10)78Si12B10 was used as a magnetically sensitive thin film due to its high permeability, low coercivity (Hc), low hysteresis, ease of magnetisation and demagnetisation. SAW magnetosensitive device operating on a frequency of 200 MHz has been experimentally developed using a standard semiconductor photolithography process. A SiO2 layer was deposited on a 36° YX-LiTaO3 substrate as a waveguide, and a (Fe90Co10)78Si12B10 layer was on the top of the propagation area as a magnetosensitive film. The experimental results showed that the acoustic loss change due to the magnetic field variation was 4.63 dB within a magnetic field range of 0 Oe to ±10 Oe, which agreed with the theoretical results. The sensor had a sensitivity of 0.7546 dB Oe−1 within the range of 0–4 Oe and the lower detection limit of magnetic fields was 0.272 Oe, low hysteresis error of 0.54%, multiple repeatability error of 0.13%, excellent repeatability and stability were achieved in the experiments from the developed sensing device.

Analysis of losses in the high-speed PM BLDC motor with open slot stator core made of amorphous soft magnetic material

PurposeThe purpose of this paper is to verify results related to losses in the core of a brushless DC prototype motor, obtained using its computer FE models, by experimental tests on manufactured machines. The paper focuses on the comparison of losses in the core of a machine with a classical stator core made of an iron–silicon material (Fe–Si) and a new one made of a modern METGLAS material.Design/methodology/approachComputer models of the prototype motors were created using FEM. The designed machines were manufactured, and experimental tests were performed. To achieve high frequencies in rotating magnetic fields, motors with a stator to rotor pole ratio of 9/12 were built. Twin rotor approach was applied, as two identical rotors were built along the two geometrically identical stators made of different core materials.FindingsExperimental studies have shown the superiority of the METGLAS material over the classical Fe–Si material. Material parameters were measured directly on the prepared cores as library data used in the simulation may be incorrect due to technological processes during core production, which was also verified. Problems related to twin rotor approach have been identified. Solution to the problem has been suggested. Necessity of 3D FEM modelling was identified.Originality/valueThe main source of originality is that METGLAS material used in the prototype machines was developed and manufactured by the authors themselves. Original approach to core parameter evaluation based on simplified methodology has been suggested. Another original part is a simplified methodology applied to loss measurement during no-load test.

Study on the Sensitivity of Detachable Wear Particle Sensor Based on Iron-Based Amorphous Soft Magnetic Rings

A parallel three-coil wear particle sensor is innovatively proposed with the detachable substrate and magnetic rings. The magnetic rings are designed and fabricated using polydimethylsiloxane (PDMS) and iron-based amorphous soft magnetic material (IASM). The excitation coils surround the magnetic rings, leaving only a 1mm air gap on the inner side (near the flow channel). The magnetic rings are magnetized under the action of the high-frequency alternating magnetic field, which forms an enhanced magnetic field with a high gradient distribution in the detection area. Through numerical simulation and experimental verification, the influence of IASM concentration, radial position and size of wear particles on the sensor output signal are studied. With the increase of IASM concentration, the sensor detection sensitivity rises dramatically. The sensor with 75&#x0025; IASM magnetic rings can effectively detect 60 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> iron particles and 160 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> copper particles in a 10mm flow channel; the detection error rate is less than 15&#x0025; in the actual lubrication circuit, which fully meets the needs of early abnormal wear fault diagnosis of mechanical equipment. Therefore, this method is a promising candidate for developing the large-flow electromagnetic wear particle sensor sensitivity.

Experimental Study on Electromagnetic Shielding Characteristics of a Fe-Based Amorphous Soft Magnetic Composite

An Fe-based amorphous soft magnetic composite with flexibility and elasticity was fabricated to shield harmful electromagnetic waves in industrial and military defense applications. Through the combination and structural arrangement of the amorphous soft magnetic sheet and the conductive sheet, the inlet (POE) form of electromagnetic waves was artificially diversified, and shielding performance was measured according to the criteria of MIL-STD-188-125-1 in the range from 1 kHz to 10 GHz, in consideration of the electromagnetic pulse (EMP) protection. As a result, the shielding effectiveness of 80 dB was achieved in a triple “sandwiched” structure by alternately stacking an iron-based amorphous soft magnetic material on top of a flexible conductive sheet at a 90-degree angle, rather than in parallel.

A Study on the Optimization of Metalloid Contents of Fe-Si-B-C Based Amorphous Soft Magnetic Materials Using Artificial Intelligence Method

A Study on the Optimization of Metalloid Contents of Fe-Si-B-C Based Amorphous Soft Magnetic Materials Using Artificial Intelligence Method

The effects of post-processing on longitudinal magnetostriction and core losses of high saturation flux density FeSiBC amorphous alloy ribbons and cores

Fe-based amorphous soft magnetic materials play an attractive role in energy saving and emission reduction due to low core losses. One of the problems is the acoustic noise resulting from magnetostriction during AC magnetization process. In this work, amorphous ribbons with a nominal composition of Fe81.5Si4B14C0.5 (at. %) were produced by planar flow casting and subjected to various postprocessing treatments. The influences of annealing conditions on the longitudinal magnetostriction, acoustic noise and core losses of the ribbons measured at low-field were studied. The effects of bending stress and epoxy impregnation and curing on medium frequency core losses of the alloy cores with different shapes were also investigated. It is shown that larger longitudinal magnetostriction of amorphous ribbons leads to higher acoustic noise emission from amorphous cores. Although the longitudinal magnetostriction was found to be reduced by applying a longitudinal magnetic field during annealing, the core loss was increased. The minimum longitudinal magnetostriction value at 1000 A/m is 7 ppm for ribbon annealed at 350 °C for 90 min. under an applied longitudinal magnetic field, while the lowest core losses at 1.4 T and 50 Hz is 0.213 W/kg for toroidal core annealed at 350 °C for 90 min. under an applied transverse magnetic field. The coupling between longitudinal magnetostriction and bending stress of amorphous ribbon results in an increase in core losses. Furthermore, extra stress was introduced after epoxy impregnation and curing, which also results in an increase in core losses. Thus, low longitudinal magnetostriction is important for stress insensitivity and soft magnetic properties.

Preparation of gas-atomised amorphous soft magnetic powders with high saturated magnetisation above 1.25 T realised by senary Fe73Si9−x B10P5C3Mo x alloys with abnormal glass-forming ability

ABSTRACT Micron-scale powdered amorphous soft magnetic materials are highly pursued for miniaturised and high-efficiency power inductors working at high frequencies due to their excellent soft magnetic properties such as extremely low coercivity and high electrical resistivity originated from the disordered atomic structures and zero magnetocrystalline anisotropy. However, the limited glass-forming ability (GFA) of amorphous soft magnetic alloys has hindered the preparation of amorphous soft magnetic powders through gas atomisation. Here, we present the development of amorphous soft magnetic alloys based on Mo-containing alloys with abnormal GFA, and demonstrate preparation of fully amorphous soft magnetic powders fabricated through the conventional medium-cooling-rate gas atomisation process. Our Mo-containing Fe73Si9 −x B10P5C3Mo x alloy showed fully amorphous state in a ribbon form with thickness up to 179 μm. Gas atomisation performed using the alloy produced fully amorphous powder with diameter up to 75 μm, while possessing high saturation magnetisation of 1.25 T.

Influence of Annealing Temperature on the Crystallization Kinetics of Fe82Si8B10 Amorphous Ribbon

Amorphous soft magnetic materials have significant potential applications in specialist power transformers and in inductive devices. With the composition of Fe82Si8B10, 82% of the transition metals Fe and about 18% of metalloid or glass-former elements like B and Si are strongly magnetic at room temperature and offer dynamic opportunities for engineering applications. The crystallization kinetics has been studied by differential thermal analysis (DTA). The sample was annealed in a controlled way in the temperature range of 350-450°C at constant annealing time one hour. The kinetics of primary crystallization α-Fe(Si) phase and secondary crystallization Fe2B phase was studied as affected due to temperature. The sample annealed at 350oC temperature is almost unchanged which is still lower than that of primary crystallization temperature but the same condition when sample annealed at 450°C completely shows that the primary crystallization α-Fe(Si) phase has vanished and crystallization event took place to a good extent.&#x0D; Journal of Engineering Science 11(1), 2020, 107-112

Compositional Design of Soft Magnetic High Entropy Alloys by Minimizing Magnetostriction Coefficient in (Fe0.3Co0.5Ni0.2)100−x(Al1/3Si2/3)x System

Developing cost-effective soft magnetic alloys with excellent mechanical properties is very important to energy-saving industries. This study investigated the magnetic and mechanical properties of a series of (Fe0.3Co0.5Ni0.2)100−x(Al1/3Si2/3)x high-entropy alloys (HEAs) (x = 0, 5, 10, 15, and 25) at room temperature. The Fe0.3Co0.5Ni0.2 base alloy composition was chosen since it has very the smallest saturation magnetostriction coefficient. It was found that the (Fe0.3Co0.5Ni0.2)95(Al1/3Si2/3)5 alloy maintains a simple face-centered cubic (FCC) solid solution structure in the states of as-cast, cold-rolled, and after annealing at 1000 °C. The alloy after annealing exhibits a tensile yield strength of 235 MPa, ultimate tensile strength of 572 MPa, an elongation of 38%, a saturation magnetization (Ms) of 1.49 T, and a coercivity of 96 A/m. The alloy not only demonstrates an optimal combination of soft magnetic and mechanical properties, it also shows advantages of easy fabrication and processing and high thermal stability over silicon steel and amorphous soft magnetic materials. Therefore, the alloy of (Fe0.3Co0.5Ni0.2)95(Al1/3Si2/3)5 holds good potential as next-generation soft magnets for wide-range industrial applications.

Impedance Change Ratio and Sensitivity of Micromachined Single-Layer Thin Film Magneto-Impedance Sensor

Thin-film techniques are important in the miniaturization of electronic devices. We studied a thin-film magneto-impedance element made with Co-based amorphous soft magnetic material and developed a highly sensitive magnetic field sensor with high spatial resolution. Thin films are several micrometers thick, and show significant impedance changes as frequencies change from the megahertz to the gigahertz region. Multilayer systems are often used to achieve a large impedance change, but they typically require a complex thin-film structure and a length of several millimeters. Our thin-film sensors have lengths between 30 µm and 1 mm in a simple monolayer configuration and successfully overcome the demagnetizing field. The impedance change ratio was 300% for a 1 mm long element at 1 GHz and between 20–30% at 1 GHz for a miniaturized element of 30 µm. The sensors had a maximum sensitivity of 33.4%/Oe.

Amorphous Soft Magnetic Core for the Stator of the High-Speed PMBLDC Motor With Half-Open Slots

Several papers have appeared in recent years on the application of the amorphous soft magnetic materials in the stators of the electric motors. In our previous work, we demonstrated that the replacement of a slotless stator from the FeSi electrical steel with the stator from an amorphous alloy Metglas 2605 SA1 in a high-speed permanent magnet brushless direct current (PMBLDC) motor resulted in a substantial decrease of power losses in this stator, even by three times at the rotary frequency of 70 000 r/min. This paper was concentrated on the development of the cores for stators with half-open slots, which are technologically more difficult to produce than the slotless cores. The cores were made by cutting out suitable amount of $25~\mu \text{m}$ -thick rings from the FeSiB amorphous ribbon by a laser technique, followed by stacking up the rings and their consolidation, and suitable heat treatment of the compressed stacks. Next, the measurements of the magnetic properties of the sample cores with half-open slots were made using the Remacomp C-1200 hysteresisgraph and the Lakeshore 450 Gaussmeter. Based on the results of measurements, the sample cores of different heights (17.5 and 10 mm) were selected for application in a stator of the prototype high-speed PMBLDC motor, 800 W in rated power and with a maximum rotary speed of 60 000 r/min. The preliminary performance tests with this prototype motor showed that after 1 h of uninterrupted operation, the temperature of a motor housing did not exceed 60 °C. It was also found that the operating efficiency of the PMBLDC motor incorporating a stator with half-open slots, made from an amorphous material, was almost 90% over a wide range of torques (from 40 to 140 mN $\cdot \text{m}$ ).

Soft magnetic properties and giant magnetoimpedance effect in thermally annealed amorphous Co68Fe4Cr3Si15B10 alloy ribbons

Giant magnetoimpedance (GMI) effect in amorphous soft magnetic materials has been intensively investigated owing to its promising technological applications. The GMI effect can be improved when an amorphous ferromagnetic material is subjected to proper heat treatments. In present work, in order to further improve the GMI effect in amorphous Co68Fe4Cr3Si15B10 ribbons, thermal annealing is employed to optimize the GMI effect of amorphous Co68Fe4Cr3Si15B10 ribbons. Magnetic measurements show that the soft magnetic properties of ribbons were affected significantly by thermal annealing. The saturation flux density of ribbons increases with increasing annealing temperature. Optimized annealing temperature of about 400°C gives lowest coercivity, highest permeability and electric conductivity. The frequency dependence of GMI effect in annealed Co68Fe4Cr3Si15B10 ribbons is discussed in details. The maximum GMI value of about 220% and sensitivity of about 106%/Oe were achieved at the driven frequency of 3MHz in the ribbon annealed at 400°C. It is clear that the enhanced maximum GMI ratio and sensitivity for the sample annealed is caused by its increased saturated flux density, permeability, electrical conductivity and reduced coercivity.

Prediction of the Energy Losses in Soft Magnetic Alloys Based on the Magnetic Objects Theory in the Case of the Uniform Magnetic Flux Penetration

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

Amorphous Soft Magnetic Materials for the Stator of a Novel High-Speed PMBLDC Motor

This paper presents results of a research work related to the development of the production technology of the amorphous cores designed for application in permanent magnet brushless direct current (PMBLDC) motors. The cores were made from the Metglas 2605 SA1 amorphous ribbon, from which rings of the specific external and internal diameters were cut using a laser technique. Next, the rings were stacked up so as to form a core of a required height, subjected later to the consolidation by pressing, followed by an appropriate heat treatment. Finally, the cores were coated with an epoxy resin to protect them against delamination and used as stators in a prototype high-speed electric motor, 1 kW in rated power and 70 000 rpm in a rotary speed. The motor incorporating these amorphous cores was subjected to the performance tests, which confirmed their proper operation and satisfactory mechanical characteristics and efficiency. It was found that power losses in the stators from the amorphous material were considerably smaller than those in the conventional stators from the silicon steel, and they did not exceed 7 W. Therefore, an application of the amorphous soft magnetic materials in the high-speed PMBLDC motors may contribute to eliminating the need of using additional cooling systems in these motors.

Magnetization distribution of magnetic vortex of amorphous FeSiB investigated by electron holography and computer simulation

The three-dimensional spin structure of the magnetic vortex of FeSiB, an amorphous soft magnetic material, was investigated by holography observation and computer simulation. Magnetization distribution in the neighborhood of the vortex center was estimated from the phase distribution obtained by holography observation. To confirm this magnetization distribution, sample-tilting experiments were performed: when the sample was tilted with respect to the electron beam direction, the phase-image center was found to shift along the tilting axis. Finite-element computer simulation was carried out to estimate the amount of shifts of the phase-image center in the sample tilting from the experimental magnetization distributions in the no sample-tilting conditions. We found that the simulated shifts of the phase-image center were in good agreement with those in the sample-tilting experiment, thus confirming the magnetization distribution near the vortex center obtained by holography observation.

Diagnostics of structural condition of amorphous and nanocrystalline soft magnetic materials

Different structural states—microcrystalline, submicrocrystalline, nanocrystalline (with a set of grain sizes each), and amorphous—of soft magnetic materials are considered. It is analyzed how the structural state of Fe5Co70Si15B10, Fe60Co20Si5B15, Co81.5Mo9.5Zr9, and Fe73.5 − xCoxCu1Nb3Si13.5B9 amorphous alloys (x = 0, 10, 20, 30 at %) influences their magnetic characteristics in different nanocrystallization conditions. It is found that peculiarities of the fine structure and the grain size in the alloys under study correlate with their magnetic parameters and informative parameters of the Barkhausen effect.

Fabrication, structural and magnetic characterization of thin microwires with novel composition Cu 70(Co 70Fe 5Si 10B 15) 30

We report on fabrication, structural and magnetic characterization of Cu 70(Co 70Fe 5Si 10B 15) 30 microwires with total diameter of 28.2 μm and metallic nucleus diameter of 15.2 μm produced by the Taylor-Ulitovski method containing 30% of alloy composition commonly used amorphous soft magnetic material and 70% Cu. The structure consists of crystalline Cu, and mixture of ferromagnetic phases. The as-prepared Cu 70(Co 70Fe 5Si 10B 15) 30 microwires present coercivity of about 85 Oe at room temperature. Temperature dependence of coercivity is measured. Significant increase of coercivity till 135 Oe is observed at about 50 K. Magnetization measured under applied magnetic field (FC) and without magnetic field (ZFC) exhibit significant difference attributed to the inhomogeneity of as-prepared samples consisting of crystalline paramagnetic Cu matrix with ferromagnetic entities. MR related with existence of ferromagnetic grains in paramagnetic Cu matrix has been observed. This MR increases with decreasing temperature (up to 1.6% at 5 K).

Symmetric magnetic tunnel junctions with amorphous soft magnetic materials as electrodes

Results concerning the influence of the additions of Ni and Ni–Si on the TMR response, saturating magnetic field and thermal stability of symmetric FeMn/FM/Al 2O 3/FM/FeMn MTJs, with FM=(Fe 0.58Co 0.25B 0.17) 100− x M x (M=Ni, Ni–Si), are presented. The magnetoresistance ratio for the symmetric Si/SiO 2/Ta(5)/Ni 80Fe 20(5)/Fe 50Mn 50(8)/FeCoBNiSi(3.5)/Al 2O 3(1)/FeCoBNiSi(5)/Fe 50Mn 50(8)/Ta(5) MTJ structure was changed with about 9% in 20 G magnetic field, leading to a sensitivity of about 0.45%/G. This structure exhibits a field window of about 10 G and low values for the tunneling resistance of about 120 Ω and the thermal coefficient of resistance of about +60 ppm/°C.

Sensor system for early detection of heart valve bioprostheses failure

Heart valve bioprostheses usually do not need anticoagulation; however, they are threatened by an increasing time risk of degeneration. The aim of this work is to find a magnetic sensor, which could be integrated in a bioprosthesis, monitoring the prosthesis in such a way that allows to confidently forecast the failure. Several models of magnetic sensors have been tested in a hydrodynamic setup specifically manufactured, where the heart pressure, frequency and cardiac flow were simulated. Small pieces of amorphous soft magnetic material were stuck to the cusps of a bioprosthesis, and through a carefully designed electronic system, the movement of the cusps is detected at the same time that the image of the working valve is captured by a digital camera. The small pieces placed in the valve are under an external applied field of few kHz, and the magnetization signal of the pieces is acquired by means of two series connected coils. The movement of the pieces, at a cardiac simulated rhythm, induces a modulation in the amplitude of the signal detected in the secondary coils, with the same frequency as the valve movement. The modulated signal is analysed with a system consisting of an amplifier and a synchronous demodulator. The analysis of the electronic signal together with the image allows characterizing the signal changes when the valve begins to fail, preventing the bioprosthesis functional failure.

Magnetic Sensor for Early Detection of Heart Valve Bioprostheses Failure

(Received: xx Xxxx xxxx.Accepted: xx Xxxx xxxx) Heart valve bioprostheses usually do not need anticoagulation; however they are threatened by an increasing with time risk of degeneration. The aim of this work is to find a magnetic sensor, which could be integrated in a bioprosthesis, monitoring the prosthesis in such a way that allows to confidently forecast the failure. Several models of magnetic sensors have been tested in a hydrodynamic setup specifically manufactured, where the heart pressure, frequency, and cardiac flow were simulated. Small pieces of amorphous soft magnetic material were stuck to the cusps of a bioprosthesis, and through a carefully designed electronic system, the movement of the cusps is detected at the same time that the image of the working valve is captured by a digital camera. The small pieces placed in the valve are under an external applied field of few Khz, and the magnetization signal of the pieces is acquired by means of two series connected coils. The movement of the pieces, at a cardiac simulated rhythm, induces a modulation in the amplitude of the signal detected in the secondary coils, with the same frequency as the valve movement. The modulated signal is analysed with a system consisting of an amplifier and a synchronous demodulator. The analysis of the electronic signal together with the image allows characterizing the signal changes when the valve begins to fail, preventing the bioprosthesis functional failure.