Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.1-5
The Half-metallic Properties of (001) and (110) Surfaces of CsSe from the First-principles
We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of CsSe in cesium chloride and zinc-blende structures by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. From the calculated local density of states, we found that all the surfaces preserve the half-metallicity of the bulk structures. The surfaces with a greater polarity have stronger ferromagnetic properties when terminated with Se atoms; the non-polar surfaces do not change their electronic or magnetic properties considerably as compared with the bulk structures.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.6-11
Periodicity Dependence of Magnetic Anisotropy and Magnetization of FeCo Heterostructure
The magnetic anisotropy energy (MAE) and the saturation magnetization Bs of (110) FenCon heterostructures with n = 1, 2, and 3 are investigated in first-principles within the density functional theory by using the precise full-potential linearized augmented plane wave (FLAPW) method. We compare the results employing two different exchange correlation potentials, that is, the local density approximation (LDA) and the generalized gradient approximation (GGA), and include the spin-orbit coupling interaction of the valence states in the second variational way. The MAE is found to be enhanced significantly compared to those of bulk Fe and Co and the magnetic easy axis is in-plane in agreement with experiment. Also the MAE exhibits the in-plane angle dependence with a two-fold anisotropy showing that the [1Ī0] direction is the most favored spin direction. We found that as the periodicity increases, (i) the saturation magnetization Bs decreases due to the reduced magnetic moment of Fe far from the interface, (ii) the strength of in-plane preference of spin direction increases yielding enhancement of MAE, and (iii) the volume anisotropy coefficient decreases because the volume increase outdo the MAE enhancement.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.12-19
Effects of Precipitate Element Addition on Microstructure and Magnetic Properties in Magnetostrictive Fe83Ga17 alloy
The <100> oriented Fe83Ga17 alloys with various contents of NbC or B were prepared by directionally solidification method at the growth rate of 720 mm·h−1. With a small amount of precipitates, the columnar grains grew with cellular mode during directional solidification process, while like-dendrite mode of grains growth was observed in the alloys with higher contents of 0.5 at% due to the dragging effect of precipitates on the boundaries. The NbC precipitates disperse both inside grains and along the boundaries of Fe83Ga17 alloys with NbC addition, and the Fe2B secondary phase particles preferentially distribute along the grain boundaries in B-doped alloys. Precipitates could affect grain growth and improved the <100> orientation during directional solidification process. Small amount of precipitate element addition slightly increased the magnetostrictive strain, and a high value of 335 ppm under pre-stress of 15 MPa was achieved in the alloys with 0.1 at% NbC. Despite the fact that the effect on magnetic induction density of small amount of precipitates could be negligible, the coercivity markedly increased with addition of precipitate element for Fe83Ga17 alloy due to the retarded domain motion resulted by precipitates.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.20-24
Magnetic Properties of
Magnetic properties of bio-magnetic molecule ferritin have been investigated. Two ferritin samples were synthesized under different magnetic fields, 0 and 9.4 T, respectively. This work is focused on the influence of magnetic field on biomineralization process. While magnetization vs. temperature (M-T) data of both samples measured at 1000 Oe are almost identical except for low temperature region (T < 6 K), magnetization vs. field (M-H) data show noticeable difference. From an analysis of M-H data by using a modified Langevin function, we could extract the saturation magnetization
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.25-28
Effect of Deformation Temperature on Crystal Texture Formation in Hot Deformed Nanocrystalline SmCo5 Permanent Magnets
In the present study, bulk anisotropic nanocrystalline SmCo5 magnets were prepared by hot deformation. The effect of deformation temperature on the texture and magnetic properties are presented, based on which the mechanism of plastic deformation and texture formation during the hot deformation process is discussed. Our analyses reveal that deformation temperature is one of the most important parameters that determine the texture of SmCo5 grains. We suggest that diffusion creep plastic deformation occurs during hot deformation, which is very sensitive to the energy gain provided by an increase in temperature.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.29-34
Magnetic Properties and Impedance Spectroscopic Studies of Multiferroic Bi1-
Nd-doped BiFeO3 materials were synthesized via a sol–gel method. The crystal structure, magnetic properties, and complex impedance spectroscopy of multiferroic Bi
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.35-39
Amorphous Cr-Ti Texture-inducing Layer Underlying (002) Textured bcc-Cr alloy Seed Layer for FePt-C Based Heat-assisted Magnetic Recording Media
Cr100-xTix amorphous texture-inducing layers (TIL) were investigated to realize highly (002) oriented L10 FePt-C granular films through hetero-epitaxial growth on the (002) textured bcc-Cr80Mn20 seed layer (bcc-SL). As-deposited TILs showed the amorphous phase in Ti content of 30 ≤
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.40-45
Nickel Substitution Effects on Nano-sized Co, Mn and MnZn Ferrites Synthesized by Sol-gel Method
Nickel substituted nano-sized ferrite powders, Co1-xNixFe2O4, Mn1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 (0.0 ≤ x ≤ 0.2), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in Co1-xNixFe2O4 ferrite but increased for the Mn1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites. For the Co1-xNixFe2O4 and Mn1-xNixFe2O4 (0.0 ≤ x ≤ 0.2) ferrite powders, the Mössbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe3+ ions. However, the Mössbauer spectrum of Mn0.8Zn0.1Ni0.1Fe2O4 consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the Mössbauer spectra could be used to determine the cation distribution equation, and we also explain the variation in the Mössbauer parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the Co1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites but increased in the Mn1-xNixFe2O4 ferrite with nickel substitution. The coercivity decreased in the Co1-xNixFe2O4 and Mn1-2xZnxNixFe2O4 ferrites but increased in the Mn1-xNixFe2O4 ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.46-50
Photocatalytic Degradation of Oxytetracycline Using Co-precipitation Method Prepared Fe2O3/TiO2 Nanocomposite
Fe2O3/TiO2 nanocomposite were successfully synthesized by co-precipitation method using Fe (NO3)3·9H2O and Ti (SO4)2 as raw materials. Structural and textural features of the mixed oxide samples were characterized by X-ray diffractometer, field emission scanning electron microscopy and energy-dispersive X-ray. The effects of initial concentration of oxytetracycline (OTC), different competitive ions and organics on the photocatalytic degradation rate of OTC by the Fe2O3/TiO2 nanocomposite were analyzed under UV and visible light irradiation. The results indicate that the optimized initial concentration of OTC was 50 mg/L to achieve the best photocatalytic efficiency. Cu2+, NH4+, C3H8O and EDTA in the aqueous suspension were found to suppress the degradation rate of OTC, whereas the effect of NO3− and H2C2O4 can be ignored.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.51-56
Effect of Grain Boundary Modification on the Microstructure and Magnetic Properties of HDDR–treated Nd–Fe–B Powders
The microstructure and magnetic properties of HDDR–treated powders after grain boundary diffusion process (GBDP) with Nd–Cu alloy at different temperatures have been studied. The variation of GBDP temperature had multifaceted influences on the HDDR–treated powders involving the microstructure, phase composition and magnetic performance. An enhanced coercivity of 16.9 kOe was obtained after GBDP at 700 ℃, due to the modified grain boundary with fine and continuous Nd–rich phase. However, GBDP at lower or higher temperature resulted in poor magnetic properties because of insufficient microstructural modification. Especially, the residual hydrogen induced phenomenon during GBDP strongly depended on the GBDP temperature.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.57-60
Detection of Corrosion and Wall Thinning in Carbon Steel Pipe Covered With Insulation Using Pulsed Eddy Current
Non Destructive Testing (NDT) methods that are capable of detecting the wall thinning and defects through insulation and cladding sheets are necessary. In this study we developed a Pulsed Eddy Current (PEC) system to detect wall thinning of ferro magnetic steel pipes covered with 95 mm thick fiber glass thermal insulator and shielded with aluminum plate of thickness 0.4 mm. In order to confirm the thickness change due to wall thinning, two different sensors, a hall sensor and a search coil sensor were used as a detecting element. In both the cases, the experimental data indicates a considerable change in the detected pulse corresponding to the change in sample thickness. The thickness of the tube was made to change such as 2.5 mm, 5 mm and 8 mm from the inner surface to simulate wall thinning. Fast Fourier Transform (FFT) was calculated using window approach and the results were summarized which shows a clear identification of thickness change in the test specimen by comparing the magnitude spectra.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.61-64
Preparation and Electromagnetic Properties of an Electromagnetic Wave Absorber
In this study, we report the as-prepared MgO-doped BaFe12O19, which was prepared by calcination technique and high-energy ball milling process, as an electromagnetic wave absorber. The phase analysis of BaFe12O19 and the as-prepared MgO-doped BaFe12O19 was detected utilizing X-ray Diffractometer (XRD). The microstructure was characterized using Scanning Electron Microscope (SEM). By means of the transmission/reflection coaxial line method, the electromagnetic properties and microwave absorbing properties of the as-prepared electromagnetic wave absorber were studied. It is found that the electromagnetic wave absorber has a minimum reflection loss value of –41 dB at 4.27 GHz with a matching thickness of 2.6 mm. The experiment results revealed that the as-prepared electromagnetic wave absorber could find potential applications in many military as well as commercial industries.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.65-71
Novel Design and Research for a High-retaining-force, Bi-directional, Electromagnetic Valve Actuator with Double-layer Permanent Magnets
To increase the retaining force, a novel design for a concentric, bi-directional, electromagnetic valve actuator that contains double-layer permanent magnets is presented in this paper. To analyze the retaining-force change caused by the magnets, an equivalent magnetic circuit (EMC) model is established, while the EMC circuit of a double-layer permanent-magnet valve actuator (DLMVA) is also designed. Based on a 3D finite element method (FEM), the calculation model is built for the optimization of the key DLMVA parameters, and the valve-actuator optimization results are adopted for the improvement of the DLMVA design. A prototype actuator is manufactured, and the corresponding test results show that the actuator satisfies the requirements of a high retaining force under a volume limitation; furthermore, the design of the permanent magnets in the DLMVA allow for the attainment of both a high initial output force and a retaining force of more than 100 N.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.72-77
Optimal Design for Thrust Ripple Reduction of Stationary Distributed-Armature System
Although the initial cost of permanent-magnet linear synchronous motors is high owing to the installation of armatures over the full length of the transportation lines, linear motors are useful for transportation systems because of their high speed, acceleration, and deceleration. For these reasons, research into reducing the cost of linear motors is necessary, and a stationary distributed-armature system has been suggested for installing armatures in sections where acceleration and deceleration of the mover are required. However, each armature has ends that significantly increase the cogging force, resulting in the increase in the thrust ripple of the mover. Therefore, in order to improve the thrust ripple of the system, the present study aims to provide auxiliary teeth on both ends of the armature to achieve an optimal design through an analysis of the contribution ratio with respect to factors regarding the design of the experiment and the objective function.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.78-82
Effect of Slot Opening on the Cogging Torque of Fractional-Slot Concentrated Winding Permanent Magnet Brushless DC Motor
Cogging torque will affect the performance of a permanent magnet Brushless DC Motor (BLDCM), thus the reduction of cogging torque is key for BLDCM optimization. In this paper, the phase shifting of cogging torque for a fractional-slot concentrated winding BLDCM is analyzed using the Maxwell tensor method. Moreover, a 9-slot 10-pole concentrated winding BLDCM driven by ideal square waveform is studied with the finite element method (FEM). An effective method to reduce the cogging torque is obtained by adjusting the slot opening. In addition, the influences of different slot openings on back electromotive force (back-EMF), air gap flux density and flux linkage are investigated and experimentally validated using the prototype BLDCM.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.83-93
Multilevel Inverters Power Topologies and Voltage Quality: A Literature Review
Due to their performances and inherent benefits, especially in medium-voltage and high-power applications, multilevel inverters have received an increasing attention in real world industrial applications. The present paper deals with a review of the main multilevel inverter topologies as well their most common derived and hybrid structures quoted in previous research works. It also encompasses an investigation on voltage harmonic elimination and THD estimation. For that reason, the paper summarizes the most relevant modulation techniques used so far to enhance the output voltage quality. Theoretical formulas evoked in the literature, for calculating the output voltage THD upper and lower bounds are reported and verified by adequate simulations.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.94-101
Analysis of an Interior Permanent-Magnet Machines with an Axial Overhang Structure based on Lumped Magnetic Circuit Model
This paper shows a new magnetic field analysis of an interior permanent magnet (IPM) machines with an axial overhang structure wherein the rotor axial length exceeds that of the stator. The rotor overhang used to increase torque density of the radial flux machine is difficult to analyze because of extra consideration of axial direction, and thus it is general for machine designer to take 3-D finite element analysis (FEA) capable of considering both radial and axial complicated geometry in the machine. However, it requires too much computing time for preliminary design especially for optimization process. Therefore, in this paper a 2-D analytic method using a lumped magnetic circuit model (LMCM) is proposed to overcome the problem. For the analysis of overhang effect, the magnetic circuit is separated and solved from overhang and non-overhang regions respectively. For the validation of proposed concept, 3-D finite element analysis (FEA) is performed. From the analysis results, it is shown that our new proposed method presents good performance in terms of calculating electromotive force (EMF) and torque within a short time. Therefore, the proposed model can be useful in design of IPM with an overhang structure.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.102-109
New Experimental Investigation of Magnetic and Electric Fields in the Vicinity of High-Voltage Power Lines
In this paper, the theoretical and experimental characteristics of magnetic and electric fields in the vicinity of high voltage lines are investigated. To realize these measurements and calculations, we have developed some equations for two overhead power line configurations of 150 kV (single circuit, double circuit), based on Biot-savart law, image and Maxwell theories, in order to calculate the magnetic and electric fields. The measurements were done to a maximum distance from the tower of 50 m, at a height of 1m from the ground. These experiments take into consideration the real situations of the power lines and associated equipment. The experimental results obtained are near to that of the Biot-Savart theoretical results for a far distance from the tower; and for a distance close to the power line, the results from the image theory are in good agreement with the experimental results.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.110-114
Parametric Analysis of Tubular-Type Linear Magnetic Couplings with Halbach Array Magnetized Permanent Magnet by Using Analytical Force Calculation
Magnetic couplings are widely used in various industrial applications because they can transmit magnetic force without any mechanical contact. In addition, linear couplings have many advantages. For example, they do not need to convert rotary motion to linear motion. This paper shows an analytical analysis of tubular type linear magnetic couplings (TLMCs) with a Halbach array magnetized permanent magnet (PM). An analytical method for magnetic fields owing to PMs is performed by using magnetic vector potential as well as Poisson and Laplace equations. Then, the magnetic force is calculated by using the Maxwell stress tensor. The analytical analysis results were compared with finite element method (FEM) results. In addition, we predicted the magnetic force characteristic according to design parameters such as the iron core thickness, inner PM thickness to -outer PM thickness ratio, PM segment ratio of the axial magnetized PM segment and radial magnetized PM segment, and various pole numbers.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.115-124
Effects of Contrast Agent Concentration on the Signal Intensity and Turbo Factor of TSE and Slice-selective IR in T1-weighted Contrast Imaging
The present study analyzes T1 TSE and T1 slice sel. IR (dark_fluid) signal strength according to the degree of gadolinium contrast agent dilution and analyzes the turbo factors with regard to changes in the maximum and overall signal strength to study correlations between changes and signal-to-noise ratios (SNRs) and compare peak-to-peak SNR (PSNR) enhancement in order to improve the quality of T1-weighted images. Enhancement TR (600 msec) evaluated to determine the T1 TSE turbo factor and obtain the maximum signal strength, T1WI were used sequentially to experiment with turbo factors_1–4. T1 slice sel. IR (dark–fluid) was used to sequentially test turbo factors_2–5 but not turbo factor_1 at a TR (1500 msec) and compare data at an increase in T1 of 900 msec. The T1 TSE was reduced according to the contrast agent concentration. Phantom signal strength increased, whereas turbo factors_1–4 exhibited maximum signal strength at a concentration of 3 mmol, followed by a gradual decrease. In the turbo factors_2–5, the signal strength increased sharply to maximum signal strength at 0.7 mmol, followed by a reduction. T1 TSE had a greater maximum signal strength than did T1 slice sel. IR (dark_fluid). A comparison of SNR found that T1 TSE imaging was superior (33.3 dB) in turbo factor_1 and T1 slice sel. IR (dark_fluid) was highest (33.9 dB) at turbo factor_5. A PSNR comparison analysis was not sufficient to distinguish between the images obtained with both techniques at 30 dB or higher under all experimental conditions.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.125-132
Buffer-Optimized High Gradient Magnetic Separation
High gradient magnetic separation (HGMS) is the most commonly used magnetic cell separation technique in biomedical science. However, parameters determining target cell capture efficiencies in HGMS are still not well understood. This limitation leads to loss of information and resources. The present study develops a bead-capture theory to predict capture efficiencies in HGMS. The theory is tested with CD3- and CD14-positive cells in combination with paramagnetic beads of different sizes and a generic immunomagnetic separation system. Data depict a linear relationship between normalized capture efficiency and the bead concentration. In addition, it is shown that key biological functions of target cells are not affected for all bead sizes and concentrations used. In summary, linear bead-capture theory predicts capture efficiency (
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.133-140
The Effects of Nonmagnetic Bolus on Contralateral Breast Skin Dose during Tangential Breast Irradiation Therapy
In this study the contralateral breast skin dose was decreased. It was to apply the results to the clinical study after analysis of different radiation dose amounts to contralateral breast with nonmagnetic bolus and without nonmagnetic bolus. A Rando phantom was computed tomography (CT) simulated, five treatment plans were generated: open tangents, open field in field, wedge 15, wedge 30, and intensity-modulated radiotherapy (IMRT) plan with 50.4 Gy to cover sufficient breast tissue. Contralateral breast skin dose was measured at 8 points using a glass dosimeter. The average contralateral breast dose using nonmagnetic bolus showed better excellence in decreasing the absorbed dose in the order of 168 ± 11.1 cGy, 131 ± 10.2 cGy (29%), 112 ± 9.7 cGy (49%), and 102 ± 9.5 cGy (64%) than changing the treatment plan. This study focused on decreasing the effect of scattered dose by use of a nonmagnetic bolus on the contralateral breast during radiotherapy in breast cancer patients and an intriguingly significant decrease was observed parallel to the opposed beam.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.141-147
The Effect of Rotating Magnetic Field on Enterotoxin Genes Expression in Staphylococcus Aureus Strains
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.148-152
Evaluation of Modified Turbo Spin Echo Technique Compared with Double Inversion Recovery Technique in Acquisition of Black Blood Brain Vessel Image
The main goal was to evaluate effectiveness of a modified TSE sequence compared with DIR (double inversion recovery) sequence in acquisition of fast flow brain vessel images using signal void effect. 32 healthy volunteers (10 men and 22 women; mean age of 31 years; ranging between 28-43 years) who underwent black blood DIR sequence (group A) and the modified TSE sequence (group B) were enrolled in our study. Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) of the internal carotid arteries’ lumen were compared in T1 and T2 weighted images for both group A and B. The images obtained from group B showed lower SNR values in internal carotid artery than the group A in both of the T1 and T2 weighted images (11.49% and 13.66% respectively). While the CNR values were higher in the group B than the group A in both of the T1 and T2 weighted images (8.69% and 7.55 % respectively). The qualitative score of all categories were not significantly different between the two groups. Furthermore approximately 49% of the total scan time was reduced from group B. Our study is to shorten the scanning time and minimize the inconveniences of the patients in acquisition of the black blood images of brain by using the signal void effect in the modified TSE technique while keeping the diagnostic value of the test.
Journal of Magnetics, 31 Mar 2016, Vol.21 , No.1, pp.153-158
Non Darcy Mixed Convection Flow of Magnetic Fluid over a Permeable Stretching Sheet with Ohmic Dissipation
This paper aims to discuss the Non Darcy boundary layer flow of non-conducting viscous fluid with magnetic ferroparticles over a permeable linearly stretching surface with ohmic dissipation and mixed convective heat transfer. A magnetic dipole is applied “a” distance below the surface of stretching sheet. The governing equations are modeled. Similarity transformation is used to convert the system of partial differential equations to a system of non-linear but ordinary differential equations. The ODEs are solved numerically. The effects of sundry parameters on the flow properties like velocity, pressure, skin-friction coefficient and Nusselt number are presented. It is deduced the frictional resistance of Lorentz force decreases with stronger electric field and the trend reverses for temperature. Skin friction coefficient increase with increase in ferromagnetic interaction parameter. Whereas, Nusselt number decrease.