Application Of Magnetic Materials Research Articles

Oblique Incidence Performance of Microwave Absorbers Based on Magnetic Polymer Composites

Recently, there has been an increasing interest in the application of magnetic materials for radar absorbing materials design [1]. Many studies have been carried out to obtain magnetic composite material with high and matching permeability and permittivity [2], because absorbers based on such materials can provide a specified level of RCS reduction and a broad bandwidth with smaller thick-ness[3]-[5]. Many magnetic absorbers (MAs) with promising oblique incidence performance at the desired frequency are based on high permeability and permittivity. However, there is a lack of basic mechanisms about oblique incidence performance for MAs based on electromagnetic (EM) parameters.

Effect of Cu doping on structural and magnetic properties of antiperovskite Mn3Ni(Cu)N thin films

Antiperovskite Mn3Ni(Cu)N thin films with different Cu content were prepared on Si substrate by reactive magnetron sputtering. The effects of Cu addition on the crystal structure, surface morphology and magnetic property of Mn3Ni(Cu)N thin films were investigated. As a result, the preferred orientation is independent to Cu-doping in the Mn3Ni(Cu)N phase, while the addition of Cu induces the lattice expansion for the films, indicating the possibility of controlling the crystal orientation and the substitution of Cu for Ni. Correspondingly, the surface morphologies significantly vary with the Cu-doping. In particular, it is found that increase in Cu content changes the ground state from antiferromagnetic (AFM) to ferrimagnetic (FI) phase and the magnetic transition temperature gradually decreases within the testing temperature ranges, which is mainly attributed to the competition between FI and AFM interactions with increasing Cu-doping content. The present discovery highlights the potential application of magnetic materials.

A novel Fe2O3 rhombohedra/graphene composite as a high stability electrode for lithium-ion batteries

Abstract

Quantitative determination of site-specific magnetic structure in TEM

Determining the magnetic structure of material on a nanometer scale is fundamental for understanding its nano-scale magnetic property and developing nano-scale magnetic devices. Site-specific electron energy-loss magnetic chiral dichroism (site-specific EMCD[1],[2]) method is come up with to get the crystallographic site-specific magnetic information of nanostructures. By constructively using the dynamical diffraction conditions in EMCD experiments, we experimentally achieve the crystallographic site-specific magnetic structure of a nanostructure of NiFe2O4 as an example in transmission electron microscope, with its site-specific magnetic circular dichroism spectra, and its site-specific spin/orbital magnetic moments extracted. The site-specific EMCD method shows its unique capability for solving the crystallographic site-specific magnetic structure on nano-scale, compared with X-ray magnetic circular dichroism and neutron diffraction. This work may benefit the research and application of magnetic materials on a nanometer scale. Acknowledgement: This work is financially supported by National 973 Project of China (2009CB623701) and Chinese National Nature Science Foundation (11374174,51390471 ). This work made use of the resources of the Beijing National Center for Electron Microscopy.

Essence of superparamagnetism in cadmium ferrite induced by various organic fuels via novel solution combustion method

An attempt has been made to enumerate the myriads of successful applications of magnetic materials in nano-regime via low-temperature solution combustion synthesis of cadmium ferrite using different organic fuels such as urea, oxalyl dihydrazide (ODH), glycine and ethylene glycol giving rise to 1D nanorods and monodispersed spherical nanoparticles, thereby exploring their applicability in nanoelectronic devices such as high speed integrated circuits as well as in biomedical field as contrasting agents used in magnetic resonance imaging (MRI) with enhanced magnetization. Thus, with appropriate selection of organic fuel and precursors (metal nitrates), single phase, cubic structured cadmium ferrites have been synthesized as depicted from FTIR spectroscopy and XRD patterns with particle size lying in 12–27nm regime as rendered from TEM micrographs. Magnetic studies in the shadow of Mössbauer studies prelude to the emergence of superparamagnetism with non-saturation of M–H loop and negligibly small values of remanence as well as coercivity at room temperature, hence attributing to its single domain as well as soft magnetic character. Moreover, the room temperature dielectric measurements show dispersion behavior with increasing frequency corresponding to low dielectric losses, hence making them suitable for applications in high-frequency devices. Thus, solution combustion methodology was successfully used as a key step in the synthesis of CdFe2O4 with highly superparamagnetic and soft character, thereby leading to products with different morphologies in nano-regime.

Nanostructured Magnetic Materials for Applications in Electrical Machines

The aim of this survey is to design a low energy production wind generator for home or small industrial use, with short blades or different structure. Magnetic materials such as strontium hexaferrites and Nd-Fe-B composites are used in form of plastic bonded magnetic powder or laminas in the rotor and amorphous material or silicon steel in the stator. The envisaged machines are switched reluctance and permanent magnet, while preferable structure is this of vertical axis. Before the construction, both inside and outside rotor design machines, also toroidal stators can be tested, using finite element method and simulation programs such as ANSYS, COMSOL. Several parameters are examined, such as torque, magnetic field orientation and strength, magnet topology, output, etc, in order to achieve low cogging force along with high power. The results are to be compared with currently manufactured machines characteristics so as to decide for the efficiency of further investment.

Effective Application of Magnetic Material Based on Metamaterial Absorber

We simulate, fabricate and measure a microwave absorber by introducing metamaterial design method to magnetic material. The proposed absorber is composed of periodic copper wire array, magnetic material coated on copper wires, a foam substrate and a bottom metal plane. The results show a nearly perfect absorption peak around 8.7GHz (simulated) and 7.6GHz (measured). Even though the electric and magnetic field distribution indicate that the absorption is a typical metamaterial absorption, the power loss is neither Ohmic nor dielectric loss but magnetic loss, which is different from typical metamaterial absorber. The skillful introduction of the magnetic loss improves the absorption performance, including the absorption bandwidth and intensity. The designed absorber shows an effective application of the magnetic material, which is only 1/60000 volume proportion of the total absorber. Dependences of the absorption on frequency and the coating volume of the magnetic material manifest that the coated magnetic material can adjust the absorption peak position and intensity. The absorber can be an attractive candidate of electromagnetic wave absorber.

Ultra-High-Frequency Behavior of BaFe$_{12}$O$_{19}$ Hexaferrite for LTCC Substrates

M-type barium hexaferrite (BaFe12O19) is investigated with an aim of using with low temperature co-fired ceramic (LTCC) substrate material. The as-calcined powders from combustion synthesis at neutral and acidic precursor solutions are used, which exhibit excellent properties of low coercive field values (up to 1350 Oe) and high magnetization (up to 60 emu/g). With an appropriate amount of Bi2O3 as sintering aid, high density ferrites have been realized at LTCC processing temperatures. The sintered ferrites possess bulk resistivity in excess of 109 Ω·cm, indicating their suitability for high-frequency applications. Complex magnetic permeability and magnetic loss factors are studied up to 1 GHz frequency. Complex permeability between 1.2 to 2.2 and magnetic loss tangent between 0.05-0.5 have been realized for the sintered ferrites. The influence of Bi2O3 content on resistivity and high-frequency magnetic properties is discussed. It is observed that the sample prepared by employing neutral pH during combustion preparation and calcined at 1200°C for 12 h shows low coercivity of 1350 Oe. After sintering at 900°C with 2 wt% Bi2O3, the sample shows better results with permeability of 1.5-1.7, magnetic loss tangent below 0.3 up to 700 MHz frequency and a high resonance frequency of 140 and 715 MHz in VHF and UHF band, respectively. Since the synthesis conditions provide better control over basic magnetic properties, the use of combustion synthesized BaFe12O19 material augers well for magnetic materials applications in LTCC technology.

Yttrium Iron Garnet: Properties and Applications Review

Due to a fast progress in the development of communication systems, the dielectric and magnetic ceramics (ferrites) have become attractive to be used in devices. Although the ferrites of the spinel type were the first material to be used in the microwave range, garnets have smaller dielectric losses and, therefore, are chosen for many applications. High demands for modern electric applications in magnetic materials results in new techniques and products being permanently studied and researched, with a consequent appearance of new solutions for a wide applications series. This work presents the study of the ferrimagnetic composite, constituted by Y3Fe5O12 (YIG) and Gd3Fe5O12 (GdIG) phases, through solid state synthetic route and submitted to high-energy mechanical milling. Additionally, experiments were made in order to evaluate the electric and magnetic behavior of the composites at radio frequency and microwave range and then later suggest an adequate technological application. The composites were efficient as ferrite resonator antennas (FRAs) and microstrip antennas (thick films deposited on metalized surface alumina substrate by screen-printing technique), in the microwave frequency range. The experiments with FRAs showed satisfactory results due to the control of the antennas radiation characteristics and their tuning by the use of an external magnetic field. The composite resonators studied in this work can be important to the development of a third generation (3G) wideband antennas to cell phones and other wireless products.

Application of magnetic materials in analysis on Chinese herb medicines

China is the cradle of Chinese herb medicines,with rich plant resources. However, traditional processing methods have many disadvantages, such as high comsumption of organic solvent, long extraction time and high loss of effective constituents. For the purpose of rational use of Chinese herb medicines and accurate analysis on their constituents,the sample pre-treatment method with magnetic nanoparticles as the carrier brought new opportunities in recent years. after consulting literatures,the essay summarizes traditional extraction methods of Chinese herb medicines, characteristics of magnetic materials and their application in the analysis on Chinese herb medicines.

Efficient adsorption and desorption of Cu2+ by a novel acid-resistant magnetic weak acid resin

A novel magnetic weak acid resin NDMC-1 was prepared in the presence of methyl acrylate (MA), divinylbenzene (DVB) and titanate coupling agent (TCA) coated g-Fe2O3 particles. To evaluate the adsorption of Cu 2+ on the obtained resin NDMC-1, another two magnetic resins NDMC-0 (the precursor of NDMC-1 without hydrolyzation) and NDMO-1 (the synthesized weak acid resin using oleic acid coated g-Fe2O3) were chosen for comparison. The results showed that the carboxyl groups were formed after hydrolyzation, and NDMC-1 exhibited a greater adsorption capacity to Cu 2+ . The desorption experiment demonstrated that the desorption ratio at pH 2 (95.14%) was greatly higher than pH 3 (25.97%). Moreover, the magnetic resin NDMC-1 was proved to be stable at pH 2, extending the application of magnetic materials which were always considered to be acid-nonresistant. # 2012 Ai Min Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Application of Magnetic Material in Magneto Suction Cupule of Crane

In order to realize safety, saving energy and material in the design and manufacture of the magneto suction cupule of crane, This text discussed how to select the permanent magnetic material and soft magnetic material, how to design the magnetic circuit and the method of magnetization and demagnetization and so on. It is emphasized on the structure of magneto suction cupule of crane made of AlNiCo and NdFeB permanent magnetic material or the combination of the two kinds of material, the application of RLC circuit in magnetizing and demagnetizing with pulse current to realize the light weight and low cost for the magneto suction cupule of crane.

ChemInform Abstract: Preparation, Characterization and Potential Application of Magnetic Materials as Sorbents for the Removal of Contaminants

AbstractReview: 69 refs.

Electrical Manipulation and Measurement of Spin Properties of Quantum Spin Hall Edge States

We study the effects of a gate-controlled Rashba spin-orbit coupling to quantum spin Hall edge states in HgTe quantum wells. A uniform Rashba coupling can be employed in tuning the spin orientation of the edge states while preserving the time-reversal symmetry. We introduce a sample geometry where the Rashba coupling can be used in probing helicity by purely electrical means without requiring spin detection, application of magnetic materials or magnetic fields. In the considered setup a tilt of the spin orientation with respect to the normal of the sample leads to a reduction in the two-terminal conductance with current-voltage characteristics and temperature dependence typical of Luttinger liquid constrictions.

Application of magnetic material in the determination of polycyclic aromatic hydrocarbons in tree leaves by high performance liquid chromatography

Carbon coated Fe3O4 magnetic particles (Fe3O4/C) were synthesized by hydrothermal reaction, and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and transmission electron microscopy (TEM). The material is applied to microwave-assisted extraction for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) from tree leaves. Magnetic solid-phase extraction (MSPE) parameters including elution solvents, amount of sorbents and enrichment time are optimized together with microwave extraction time, power, extraction solvents and the ratio of liquid to solid. Under the optimal conditions, the developed method provides spiked recoveries of 77.7–103.8% with RSDs of less than 4.0%, and limits of detection (LOD) of 0.5–2.0 ng g−1. PAHs in tree leaves are successfully determined.

Corrosion of Fe-Based Nanocrystalline Alloys with Soft Magnetic Properties

Abstract Iron-based nanocrystalline alloys have attracted increasing attention due to their good soft magnetic properties for industrial applications. These alloys combine low magnetic loss, high saturation magnetic flux density, low coercive force, and high permeability, which are important in soft magnetic materials applications. Corrosion not only decreases the service life of soft magnetic materials, creating the need for system replacement, but can also damage the soft magnetic properties of these alloys. This behavior can lead to serious consequences in several applications, e.g., when solenoid valves or magnetic sensors are used for controlling combustible fluids or pressure vessels. Therefore, in the past few years, considerable interest has focused on the effect of microstructure and composition on the corrosion of iron-based amorphous and nanocrystalline alloys and on the effect of corrosion on the magnetic properties of these materials. This paper describes the main families of nanocrystalline Fe-based alloys with soft magnetic properties and discusses their magnetic properties and applications. In addition, the effect of partial crystallization on corrosion resistance is examined, including a critical discussion about the mechanisms reported in the literature. Other points analyzed here are the relationship between nanocrystalline alloy corrosion and composition, the effect of main alloying elements such as Nb, Zr, and No, the effect of corrosion on the magnetic properties of nanocrystalline alloys, and trends for future investigations. The aim of this paper is to review the current body of knowledge about the corrosion of nanocrystalline Fe-based alloys with soft magnetic properties and to highlight the importance of corrosion on the behavior of nanocrystalline soft magnetic materials.

Pyrolysis synthesis of magnetic [formula omitted]- and [formula omitted]-MnO 2 nanostructures and the polymorph discrimination

The concentration of the Mn(NO 3) 2 solution has significant influence on the morphologies and the phases of the MnO 2 products. A large number of ε - MnO 2 nanowires were prepared via a simple pyrolysis under lower reaction concentration. The nanowires have lengths up to tens of micrometers and diameters in the range of 20–100 nm. The β - MnO 2 nanobundles and nanoflowers were prepared by increasing the concentration of Mn(NO 3) 2 solution. The superparamagnetism of ε - MnO 2 nanowires and paramagnetism of β - MnO 2 nanoflowers indicate their potential applications in magnetic materials.

Two Related Gadolinium Aquo Carbonate 2-D and 3-D Structures and Their Thermal, Spectroscopic, and Paramagnetic Properties

We report two new extended inorganic materials based on gadolinium. The first, [Gd(CO(3))(2)H(2)O][NH(4)], consists of negatively charged 2-D sheets of gadolinium carbonate with one coordinated water molecule and an ammonium cation between the layers. The coordinated water and one carbonate extend into the interlayer space, connecting the layers via an extensive hydrogen bonding network which includes the ammonium ions. The second, a closely related yet more condensed framework structure, [Gd(2)(CO(3))(3)NH(3)H(2)O], is formed at a higher hydrothermal temperature and was characterized by single crystal X-ray diffraction data collected at a synchrotron. This second structure contains layers that are isostructural to the first, bridged together by carbonate, and coordinated by water and ammonia. The properties of these materials were studied by thermogravimetric analysis-mass spectrometry, photoluminescence, electron paramagnetic resonance, and Raman and infrared spectroscopy. The 2-D [Gd(CO(3))(2)H(2)O][NH(4)] is stable to about 175 degrees C, though water and ammonium loss continues through the entire thermogravimetric analysis trace. The 3-D material remains intact until about 325 degrees C. Both structures exhibit broad luminescence bands in the near-ultraviolet region centered at 354 nm. Electron paramagnetic resonance and magnetic susceptibility show spin-spin coupling between adjacent gadolinium atoms in both structures and confirm that they are paramagnetic. These materials show interesting photoluminescent and paramagnetic properties that could possibly be exploited for chemical sensing or magnetic materials applications.

The Design of a Half-bridge Series-resonant Type Heating System for Magnetic Nanoparticle Thermotherapy

Application of magnetic materials for hyperthermia of biological tissue has been known, in principle, for more than four decades. Many empirical works were done in order to conflrm a therapeutic efiect on several types of tumors by performing experiments with animals or using cancerous cell cultures. The main idea of magnetic nanoparticle (MNP) thermotherapy is to utilize 7- to 50-nm diameter of ferric oxide (Fe3O4) particles which are heated up to 42 - C under AC magnetic fleld for cancer therapy applications. In order to achieve the goal of killing cancer cells using the AC magnetic fleld, we designed a heating system to generate magnetic fleld which can be focused and frequency adjustable. This study adopts the half-bridge series-resonant type circuit as the core scheme of the heating system, and utilizes the frequency-adjustable design to conduct the heating experiment. The experiment results show that the designed coil and the heating system can warm up the magnetic nanoparticle 6 - C in 32 minutes.

Preparation and magnetic properties of Fe/Si/C/N ceramics derived from a polymeric precursor

AbstractIron‐containing polysilazanes (PSZI) were prepared by the amine displacement reaction along with heat‐induced vinyl crosslinking reactions between Fe[N(SiMe2Vi)2]3 (Vi = CHCH2) and polysilazane containing SiVi (PVSZ). The PSZIs were converted into magnetic ceramics by the pyrolysis in N2. The ceramics produced were investigated by X‐ray diffraction, transmission electron microscope and vibrating sample magnetometer at room temperature. It was indicated that α‐Fe is the only magnetic crystalline embedded in the amorphous Si/C/N‐based matrix from 500 to 900°C. Moreover, the sample prepared at 500°C showed few hysteresis at room temperature, consistent with the behavior of superparamagnetic particles, which was confirmed by the zero‐field‐cooled and field‐cooled magnetization measurement. Additionally, the results indicated that the magnetic properties of the ceramics could be tuned by controlling the content of iron and the pyrolysis temperature. This flexibility may be advantageous for some particular magnetic materials applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007