Characterization Of Magnetic Materials Research Articles

Quantitative MFL characterization study in hard magnetic material surface topography measurement

Magnetic flux leakage (MFL) characterization of hard magnetic material (HMM) plays a significant role in the service performance and structural health monitoring of magnetic and mechanical parts. Quantitative simulation study and theoretical analysis in HMM surface topography inspection were conducted for the first time. Starting with the background introduction of electromagnetic theories in HMM surface topography inspection, four typical surface models and function relations were built and confirmed quantificationally. By large numbers of quantitative simulations and analysis of different HMM surface topographies, it can be found that both magnetic enhancement region and cavity exist. Furthermore, the self-magnetization effect forms the magnetic enhancement region, and magnetic cavity is mainly caused by the magnetic compression effect. Finally, the fitted function relationships applied to reconstruct the surface parameters with small estimated errors laid a solid theoretical foundation to the quantitative surface topography measurement in practical applications. Thus, an overall measurement theory for ferromagnetic material was built through the supplement of HMM surface topography characterization.

Fabrication and characterization of amphiphilic magnetic water purification materials for efficient PPCPs removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants that have gained increasing attention in recent years. Conventional adsorption materials exhibit poor efficiency in removing PPCPs. In this regard, a series of magnetic particles (Nanda Amphiphilic Materials, NDAMs) was fabricated and characterized in this study. These materials were prepared by special polymerization with different monomer proportions [N-vinyl-2-pyrrolidone (NVP)/divinylbenzene, (DVB)]. Characterization results indicated that NDAM-40 (n(NVP):n(DVB), 6:4) was the most effective and possessed the largest BET surface area (650 m2/g) among the nine prepared NDMAs. NDAM-40 also possessed the highest nitrogen content (1.13%) and the smallest contact angle (71.5°). Seventeen representative PPCPs were chosen to investigate the adsorption performance of NDAM-40. Norit, a commercial activated carbon, was used for comparison. NDAM-40 exhibited faster adsorption rate than Norit. For most PPCPs, the pseudo-second-order rate constants of NDAM-40 were more than five times higher than those of Norit. The amounts (Qe) of most PPCPs adsorbed on NDAM-40 were two to five times higher than those on Norit. NDAM-40 was applicable to water purification because of its definite advantages in terms of removal efficiency and recyclability. The removal efficiency of 17 PPCPs exceeded 80% when using NDAM-40, and only 20%–70% when using Norit.

Structural and impedance spectroscopy characterization of Soft Magnetic Materials

Abstract This work studies the relationship between the structural characteristics and the final magnetic properties of two different iron-based materials: one basic Soft Magnetic Material (SMM) and a Soft Magnetic Composite (SMC). The micrometric size of the starting powder, the pure iron composition of the core and the presence of a phosphate isolating shell in the composite sample were revealed by powder X-ray diffraction, Laser Diffraction and Fourier Transformed Infrared Spectroscopy respectively. Moreover, Scanning Electron Microscopy confirms the range of sizes of the powder samples and their non-perfect spherical shape. Magnetic and Impedance Spectroscopy measurements evidence the effects that the isolating shell has on the effective magnetic permeability and the relaxation frequency at which magnetic losses appear. Results obtained are of great interest from a technological point of view because the frequency range at which each material can effectively operate is measured. Furthermore, different structural aspects (such as particle size or the presence of an isolating shell) are related with the final functional properties. Besides, these results can help in the design of new soft magnets with lower magnetic losses over a wide range of frequencies.

Novel Ultra-Wide Band (10 MHz–26 GHz) Permeability Measurements for Magnetic Films

Magnetic materials are the necessary components of the modern rf components. The demand for higher communication speed such as the upcoming 5G network requires higher operation frequency of rf components. For example, the future spectrum band of mobile network will be extended above 24 GHz [1]. Permeability measurements provide a basis for the design and characterization of magnetic materials and the development of RF devices. However, permeability measurement results and commercially available permeameters have been limited to 9GHz or below [2]–[7]. Conventional broadband permeameters use a vector network analyzer (VNA), and a pick-up coil or an electric short [2], [3], or a broadband transmission line [4], [6] for magnetically exciting the materials under test. Inductance changes are measured at zero magnetic field and at saturation magnetic field through a vector network analyzer for extracting the permeability spectrum. The bandwidth of Pick-up coil is limited to several hundred MHz. Transmission-lines [4]–[6] are widely used for broadband permeameters. However, the transmission-line type permeameters are noisy in the frequency range below 100MHz due to the low inductance. In addition, all these broadband permeameters based on vector network analyzers are expensive, and not reliable in measuring thin films or materials with low permeability because of the low signal to noise ratio (SNR). In this article, we demonstrate a new type of permemeter for ultra-wide band permeability measurements with significantly enhanced signal to noise ratio (SNR), and demonstrate the measurements on a 50nm FeGaB film up to 22GHz and an ultra-thin 2nm NiFe film. This permeameter enables the characterization of the complex permeability between 10MHz-26GHz, as well as many other typical magnetic parameters including linewidth, saturation magnetization, effective anisotropy field, Gilbert damping, and inhomogeneous linewidth broadening. In addition, the new permeability measurement system shows $40 \sim 50$ dB higher SNR over the conventional permeameters.

An image processing method for automated evaluation of the area of hysteresis loops

Measuring the magnetic hysteresis loop and energy loss characteristics of magnetic materials helps students to understand the ferromagnetic properties of the materials. In this study, a conventional experiment is combined with automated image processing to learn about the fundamentals of the hysteresis loop by measuring its area. We process a loop image acquired using a digital camera to calculate the area. The results of this easy and instructive experiment are substantially compatible with theory and are more precise than those obtained when using the tedious conventional method of manually evaluating the loop area. The proposed method is discussed as a clear-cut and a fast tool to reproduce the results with pragmatic accuracy.

On the importance of magnetic material characterization for the design of particle accelerator magnets

In this paper, the importance of magnetic material measurements in the framework of the design of magnets for particle accelerator is discussed. In particular, five samples of different ferromagnetic materials are analyzed experimentally and compared with literature results. These materials have been (or will be) used for producing yokes for several normal-conductor magnets at CERN, such as REX-ISOLDE main dipole, ELENA dipole and quadrupole, and SESAME dipole. The comparison with literature shows several disagreements. The main one of them is analyzed in detail in a case study based on finite elements simulation of a quadrupole magnet installed in CERN. This analysis shows that a good knowledge of the yoke initial magnetization curve is important to guarantee a given level of magnet performance, especially concerning its field quality.

“Regular element” global SLAE of the finite element method when simulating electromagnetic processes of electric devices

The article is devoted to mathematical and simulation modeling of electromagnetic processes of electric devices (ED). The development of industry, transport, power facilities, agriculture, and household services, health care leads to creation of electrical devices and systems for various functional purposes. It complicates the design (geometry) of electromagnetic and magnetic systems, improves magnetic and electrical characteristics of ED materials. The development of new software and hardware allows solving mixed (connected) tasks of simulating various physical processes in ED, electrical and electromechanical systems. However, general-purpose software complicates its engineering assimilation and implementation into production. The stage of ED numerical simulation modeling based on the finite element method when their investigating and designing is offered to be reduced and cheapened by changing the process of developing a global system of linear algebraic equations (SLAE) out of the system of elemental equations. The purpose of the work is to develop an algorithm to form global SLAE based on recurrent relations for its coefficients. The study subject is quasi-variable and magneto static vector models of ED electromagnetic processes, electro technical and electromechanical systems. Tasks are: developing of a “regular element”, obtaining recurrent relations for global SLAE coefficients. Research methods are: numerical calculations based on the Galerkin’s projection-grid method along with the finite element method (FEM). Results are: a seven-point “regular element” for a regular triangulation network from triangular finite elements (FE) of arbitrary shape and rectangular triangles has been developed; recurrent relations for global SLAE coefficients have been determined; a possibility of obtaining engineering techniques for investigating ED with minimal computer’s dynamic memory expenses has been shown on the example of calculating a linear induction motor (LIM).

Effect of the surface treatment on the structural, morphological, magnetic and biological properties of MFe2O4 iron spinels (M = Cu, Ni, Co, Mn and Fe)

This research proposes to obtain iron spinels MFe2O4, and their hybrids MFe2O4@SiO2 and MFe2O4@SiO2/chitosan (M = Cu, Ni, Co, Mn e Fe) from the surface modification with (3-aminopropyl)trimethoxysilane agent and functionalization with chitosan, and then evaluate them as to their structure, morphology, magnetism and cytotoxicity, towards obtaining biocompatible hybrids for biological applications. The samples were analyzed by XRD, FTIR, SEM, TEM, magnetic measurements and in vitro cytotoxicity. XRD results showed that all samples presented the formation of the desired spinel major phase, with a crystallite size between 12 and 45 nm. According to the morphology and FTIR spectra of the samples, it was possible to confirm the formation of the hybrids. All samples presented soft magnetic material characteristics, exception given to the iron spinels CoFe2O4, which showed characteristic of hard magnetic material. The best results of cell viability were obtained by the CoFe2O4, MnFe2O4 e Fe3O4 MNPs and their hybrids.

Magnetic Sio2-Fe3O4 Nanocomposites as Carriers of Ibuprofen for Controlled Release Applications

Abstract In the present paper, we report the preparation and characterization of magnetic silica nanostructured materials that were used as ibuprofen drug molecule carriers. This work was aimed at obtaining drug release systems sensitive to a magnetic field to be directed to target sites. The preparation of the silica nanostructuredmaterials started with the synthesis of magnetite (Fe3O4) nanoparticles that were added subsequently during the hydrolysis and condensation of tetraethyl-orthosilicate (TEOS) to obtain SiO2-Fe3O4 nanocomposites. The ibuprofen molecules were added simultaneously with magnetite nanoparticles. The in vitro ibuprofen release profiles were analyzed, showing a typical controlled release for all materials studied. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning microscopy (SEM), thermogravimetric analysis (TGA), N2 adsorption-desorption isotherms; magnetic studies were also performed. The obtained materials showed low superparamagnetic values, and saturation behavior was also observed. It was demonstrated that ibuprofen does not affect the magnetic behavior of magnetite, indicating its possible use in medical applications.

In-vivo biomagnetic characterisation of the American cockroach

We present a quantitative method, utilising a highly sensitive quantum sensor, that extends applicability of magnetorelaxometry to biological samples at physiological temperature. The observed magnetic fields allow for non-invasive determination of physical properties of magnetic materials and their surrounding environment inside the specimen. The method is applied to American cockroaches and reveals magnetic deposits with strikingly different behaviour in alive and dead insects. We discuss consequences of this finding to cockroach magneto-reception. To our knowledge, this work represents the first characterisation of the magnetisation dynamics in live insects and helps to connect results from behavioural experiments on insects in magnetic fields with characterisation of magnetic materials in their corpses.

Investigations on microstructure, electrical and magnetic properties of copper spinel ferrite with WO3 addition for applications in the humidity sensors

In the present study we report the structural, electrical, magnetic and humidity characteristics of copper ferrite with different percent on tungsten trioxide addition. The aim of this study was to obtain more stable and sensitive active materials for humidity sensors. In order to highlight the influence of tungsten on the structural, electrical and magnetic properties, the ferrite samples were fabricated via sol-gel self-combustion method and sintered for 30 min at 1000 °C with percent between 0 and 20% tungsten trioxide additions. The X-ray diffraction investigations showed the copper ferrite phase composition. The scanning electron microscopy revealed the influence of the substitution on characteristics of the crystallites and the profilometry showed the surface topography of samples. The investigation was focused on the variation of permittivity and electrical conductivity, in relation with tungsten trioxide addition, frequency and humidity. We have also, investigated the relevant magnetic characteristics of the copper ferrite material by highlighting the influence of tungsten trioxide addition on to Curie temperature and the permeability frequency characteristics. The data suggests that the copper ferrite with tungsten trioxide addition can be used as active material for humidity sensors.

Physics-Based Co-Simulation Platform With Analytical and Experimental Verification for Bidirectional IPT System in EV Applications

Inductive power transfer (IPT) technology has been approved to be convenient and reliable interface for charging and discharging the electric vehicles (EVs). Precise model for such system can help designers and researchers to anticipate, optimize, and evaluate its behavior amid the development. Thus, this paper presents a physics-based co-simulation platform for the bidirectional IPT system (BIPTS) in EVs’ applications. The platform is established through the coupling between finite element and circuit analysis. The power electronic converters and controllers are developed in Simulink ; and the power pads are modeled in Magnet environment. The two parts are lined together through the compatible Simulink plug-in tool. In addition, a state-space dynamic mathematical model for the same BIPTS is derived and implemented in MATLAB environment. A 1.2 kW BIPTS is analyzed under different dynamics by both models and the results are compared. The effect of the nonlinearities and the magnetic material characteristics on the BIPTS's performance is assessed, in terms of errors and harmonics analysis. The analysis considered both the full and light loading operating conditions in the system. Finally, a small-scale prototype for a BIPTS is built, tested, and compared with the co-simulation results for verification purposes. The proposed co-simulation could provide accurate prediction for the system's dynamics, during both charging and discharging operation. The scheme is generic and can be easily expanded to different pad structures, compensation networks, and converter topologies.

Characterisation of soft magnetic materials by measurement: Evaluation of uncertainties up to 1.8 T and 9 kHz

Magnetic measurements are indispensable for the characterization of soft magnetic material used e.g. in electrical machines. Characteristic values are used as quality control during production and for the parametrization of material models. Uncertainties and errors in the measurements are reflected directly in the parameters of the material models. This can result in over-dimensioning and inaccuracies in simulations for the design of electrical machines. Therefore, existing influencing factors in the characterization of soft magnetic materials are named and their resulting uncertainties contributions studied. The analysis of the resulting uncertainty contributions can serve the operator as additional selection criteria for different measuring sensors. The investigation is performed for measurements within and outside the currently prescribed standard, using a Single sheet tester and its impact on the identification of iron loss parameter is studied.

Phenomenological description of a spin chain system with geometrical frustration of couplings

The phenomenological model, using which we can in a relatively simple way calculate many magnetic, thermodynamic and dynamic characteristics of the spin chain material with the geometrical frustration of spin-spin couplings is proposed. The results of theoretical calculations well reproduce observed details of the low-temperature behavior of the magnetization, magnetic susceptibility, specific heat, magneto-acoustic characteristics, and some dynamical properties. In particular, the model permits to explain the double peak structure of the temperature dependencies of the magnetic susceptibility, specific heat, and the renormalization of the sound velocity, and can explain several features of the ESR frequency-field diagram.

Iron Loss Characteristics Evaluation Using a High-Frequency GaN Inverter Excitation

Recently, novel magnetic materials have been developed for high-efficiency and high power density electric motors. In addition, next-generation semiconductor devices, like silicon carbide (SiC) or gallium nitride (GaN), have been introduced for power converters due to their high-frequency operation. Therefore, high-frequency operation of new magnetic materials is possible when they are driven by GaN or SiC inverters. Nevertheless, iron loss characterization of magnetic materials when they are excited by high-frequency signals have not been conducted yet. This paper introduces the iron losses characterization of a magnetic material at high carrier frequency excitation using a GANFET inverter. This characterization was carried out by the experimental evaluation of iron losses at carrier frequencies from 5 to 500 kHz at different deadtimes. As a result of the measurements, iron losses seem to have a trend to increase at high carrier frequencies and large deadtimes. In addition, filtering is introduced and it seems to be an effective technique for reducing iron losses.

Fabrication, characterization and comparison of composite magnetic materials for high efficiency integrated voltage regulators with embedded magnetic core micro-inductors

High-efficiency integrated voltage regulators (IVRs) require the integration of power inductors, which have low loss and reduced size at very high frequency. The use of a magnetic material core can reduce significantly the inductor area and simultaneously increase the inductance. This paper focuses on the fabrication, characterization and modeling of nickel zinc (NiZn) ferrite and carbonyl iron powder (CIP)-epoxy magnetic composite materials, which are used as the magnetic core materials of embedded inductors in a printed wiring board (PWB) for a system in package (SIP) based buck type IVR. The fabricated composite materials and process are fully compatible with FR4 epoxy resin prepreg and laminate. For 85% weight loading of the magnetic powder (around 100 MHz at room temperature), the composite materials show a relative permeability of 7.5–8.1 for the NiZn ferrite composite and 5.2–5.6 for the CIP composite and a loss tangent value of 0.24–0.28 for the NiZn ferrite composite and 0.09–0.1 for the CIP-composite. The room temperature saturation flux density values are 0.1351 T and 0.5280 T for the NiZn ferrite and the CIP composites, respectively. The frequency dispersion parameters of the magnetic composites are modeled using a simplified Lorentz and Landau–Lifshitz–Gilbert equation for a Debye type relaxation. Embedded magnetic core solenoid inductors were designed based on the composite materials for the output filter of a high-efficiency SIP based buck type IVR. Evaluation of a SIP based buck type IVR with the designed inductors shows that it can reach peak efficiencies of 91.7% at 11 MHz for the NiZn ferrite-composite, 91.6% at 14 MHz for CIP-composite and 87.5% (NiZn ferrite-composite) and 87.3% (CIP-composite) efficiency at 100 MHz for a 1.7 V:1.05 V conversion. For a direct 5 V:1 V conversion using a stacked topology, a peak efficiency of 82% at 10 MHz and 72% efficiency at 100 MHz can be achieved for both materials.

Study and characterization of soft magnetic materials for beam intensity monitors at CERN

At CERN, the circulating beam current measurement is provided by two types of transformers, the DC Current Transformer (DCCT) and the Fast Beam Current Transformer (FBCT). Each transformer is built based on toroidal cores made from a magnetic material. Depending on the type of measurement to be performed these cores require different magnetic characteristics for parameters such as permeability, coercivity and the shape of the magnetization curve. In order to study the effect of changes in these parameters on the current transformers, several interesting raw materials based on their as-cast properties were selected. The materials have been characterised to determine a suitable annealing processes to tailor their properties. As-cast properties such as the permeability, coercivity and Barkhausen noise have also been measured to enable the study of the effect of thermal treatment in the microstructure of the alloys, and the correlation of this with the change in the magnetic properties. The comparison of the measured properties have narrowed down the best materials for further study.

Determination of Original Nondegraded and Fully Degraded Magnetic Characteristics of Material Subjected to Laser Cutting

The degrading effect of laser cutting on steel sheet material, and thus on the material's magnetic characteristics, is much less understood than that of mechanical cutting. Furthermore, the degrading influence on the magnetic properties is still difficult to determine. This paper focuses on the modeling of the degrading influence of laser cutting on the magnetic properties of electrical steel sheets. As the degradation depth and the degradation profile are still difficult to define, a method is needed, which takes the effect of laser cutting into account, but without the need of knowing the degradation profile exactly. This paper shows that a method that does not require any information on the physical phenomena that are introduced by the cutting process and that has already been verified for mechanically cut samples can also be applied to laser-cut samples, although the deterioration mechanisms and the resulting degradation profile and depths differ. Magnetic characteristics are identified for two different material zones and subsequently inserted into a finite-element model, which accounts for arbitrary geometries. The simulation results for the influence of laser cutting on the magnetic characteristics of the stator lamination stacks are verified by measurements, including three different materials and frequencies.

First report on soapnut extract-mediated synthesis of sulphur-substituted nanoscale NdFeB permanent magnets and their characterization

Biosynthesis of nanoscale materials has its own advantages over other physical and chemical methods. Using soapnut extract as reducing and stabilizing agent for the synthesis of inorganic nanoscale materials is novel and has not been exploited to its potential so far. Herein, we report for the first time on the effects of sulphur substitution on soapnut extract-mediated synthesis of nanoscale NdFeB (S-NdFeB) permanent magnetic powders (Nd 15%, Fe 77.5%, B 7.5% and S with molar ratios: 0.1, 0.2, 0.3, 0.4, and 0.5). To synthesize, a 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the as-prepared nanoscale S-NdFeB magnetic materials was done using the techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS for size and zeta potential measurements) and vibrating sample magnetometer (VSM)–hysteresis loop studies. The results revealed that particles were highly stable (with a negative zeta potential of 25.7 mV) with irregular and spherical shape (with measured hydrodynamic diameter 6.7 and 63.5 nm). The tetragonal structures of the formed powders were revealed by XRD micrographs. Hysteresis loop studies clearly indicate the effect of S concentration on the enhanced magnetization of the materials.

Measurement of dielectric and magnetic properties of materials by means of a TDR probe: a preliminary theoretical investigation in the frequency domain

ABSTRACTThis paper is focused on the measurement of both dielectric and magnetic characteristics of a penetrable material at radio frequency through a time‐domain reflectometry probe. The goal is to prove that a time‐domain reflectometry probe can offer the possibility to discriminate the dielectric permittivity from the magnetic permeability of the material. This is due to the fact that the time‐domain reflectometry datum depends both on the propagation velocity of the electromagnetic waves in the probed medium and on the intrinsic impedance of the probe. However, the possibility to attain such a clear discrimination is bound by the condition that the reflection coefficient is measured (or calculated) along the probe at the air–soil interface in the frequency domain. Generally, time‐domain reflectometry probes measure the total (incident plus reflected) field in the time domain, and subsequently, the datum is needed to meet the condition that such claimed purpose is not just the Fourier transform of a datum collected by means of a common time‐domain reflectometry probe. Rather, either a devoted hardware should be implemented or a very accurate knowledge of the incident field should be guaranteed in order to separate the reflected wave from the incident one. In this preliminary work, our study has been restricted to a theoretical investigation in the frequency domain. In particular, our focus is set on the lossless case, and the attention is devoted to the issue of possible multiple solutions to demonstrate that this obstacle can be overcome by making the frequency step narrower or, alternatively, by narrowing the length step of the probe. Simulation results based on a bifilar transmission line model are shown.