It was recently predicted that alkali-metal-based half-Heusler compounds have robust half-metallicity with wide band gaps (1.60-2.38 eV), and the half-metallicity is retained at surface and under severe strain. In this study, we investigate the half-metallicity and electronic structure of the LiCrSb/InSb hybrid system to reveal real applicability of an alkali-metal-based half-Heusler compound to spintronics using first-principles calculations. Half-metallicity at the interface is well retained, and a proximate effect opens a gap in the minority spin band of the InSb layer with band gaps of 0.55-0.65 eV. The whole LiCrSb/InSb hybrid system prefers magnetization parallel to the plane.

The magnetostriction effect is a unique phenomenon observed in magnetic materials due to applied stress. The permeability μ of the magnetic material increases or decreases depending on the sign of the magnetostriction coefficient λ based on the direction of the applied stress. For example, nickel has a negative λ, whereas iron has a positive λ for the same tensile (+) or compressive (-) stresses. However, the magnetostriction effect is reported to disturb the functionality of some spintronic applications, such as magnetic sensors and actuators, under the influence of an external magnetic field. Therefore, suppression of the magnetostriction effect is a challenge in developing flexible spintronic devices. In this study, the magnetostriction effect of the Ni_xFe_1-x thin films was investigated under different stress conditions. The composition of the thin film was manipulated by varying the deposition thickness of nickel and Ni₈Fe₂ targets using a co-sputtering system. Magnetization reversal behaviors of the Ni_xFe_1-x thin films were observed under the influence of an external magnetic field by using a vibrating sample magnetometer (VSM), before and after the application of bending stress. The negative magnetostriction effect of nickel was decreased by increasing the iron composition in the thin film, owing to the opposite sign of the magnetostriction coefficient. Finally, an extremely low magnetostriction was achieved at x = 0.8. The results of this study suggest that the magnetostriction effect can be controlled by varying the composition of the thin films and a sufficiently small magnetostriction effect can be observed at the permalloy composition between nickel and iron.

The effect of electrostatic and magnetic vector potentials pattern on electrical properties and the tunneling magnetoresistance in graphene junction with periodic magnetic vector potentials are theoretically investigated using the transfer matrix method. The magnetic structure on graphene can control the direction of the magnetizations which correspond to the parallel and anti-parallel (AP) configurations. In AP magnetic structures with the applied gate voltage pattern, U_A (U₁ = U₂), the shift of the conductance-peak position as a function of Fermi energy. The peak corresponds to resonant tunneling, where the incidence energy of the tunneling electron equals the confinement energy, and the conductance peak decrease approximately linearly with increasing electrostatic potential. The peak position occurs at E_F = 0.5U where it is shifted to higher Fermi energy with higher gate potential, but for the case of U_B (U₁ = -U₂), the peak height is reduced rapidly, and the width increase as gate potential increases. Because of the periodic magnetic field with zero spatial average in the antiparallel structure, we found that the minimum conductivity decreases with increasing magnetic energy. They show suppression of Klein tunneling which occurs in the zero-conductance plateaus and leads to the robust magnetoresistance plateau and large positive magnetoresistance appears below magnetic energy. For the case of U_A and E_F more than magnetic energy, we found that the quasi-linear magnetoresistance feature is applied by an electric field instead of the usual magnetically driven magnetoresistance.

From the system-level design perspective, a robust design optimization method for a permanent magnetic motor is proposed to enhance the dynamic performance of a drive system while maintaining its steady performance. To achieve the goal, an elaborate numerical model for the whole drive system is first constructed by incorporating a control circuit simulator into a finite element analysis tool, and then the influence of motor parameter variations on transient system responses is investigated by means of the method of Taguchi experimental planning. A conventionally customized motor is optimized by the univariate dimension reduction method to ensure the robustness of system performances against manufacturing tolerances. Finally, a comparative performance analysis between two motor drive systems is provided to demonstrate the validity of the proposed method.

For the common technical applications of permanent magnets such as cylindrical and rectangular permanent magnets, the formula of the holding force, which is based on the idea of equivalent current source and associated with Lorentz force, is fine modified with introducing two parameters, the chamfer size of the magnet and the thickness of the outer protective film. Furthermore, the model is verified by external experimental data. The accuracy of our proposed model has been significantly improved compared to the base model, with an average improvement of 6.3 %. With external data, the average error of the refined model is within 6 %. Compared to other currently available online calculators, our calculation model offers superior calculation accuracy.

This paper first presents a general two-dimension (2D) harmonic analytical solution for the magnetic field of electric machines in the Cartesian coordinates. In this solution, the relative permeance is directly considered in Laplace and Poisson’s equations, and the particular solutions in Cartesian coordinates are solved. By applying the complex Fourier separation method, with the boundary and interface conditions, the magnetic field in the inhomogeneous region is solved from system equations. Numerical examples validate the presented method and the obtained results have a satisfactory agreement with the finite element analysis. The proposed model in this paper has a significant value for modelling electric machines, such as linear permanent magnet (PM) machines and axial flux PM machines.

This paper presents a method for calculating the iron loss of the stator core of an electric motor owing to the stress generated by shrink fit tolerance in the production process. Shrink fit is used to fix the frame and stator core, shaft, and rotor core in a motor, and the corresponding condition varies depending on the material. Three finite element analysis steps were performed to reduce the iron loss owing to stress during shrinking of a frame and stator core. In step 1, the shrink fit process was applied to a frame and stator core, considering the manufacturing tolerances through three-dimensional modeling. Thermal-structure finite element analysis was performed to apply the same conditions as those in the shrink fit process. The shrink fit was expanded by applying heat to the frame, followed by natural cooling to calculate the contact stress between the frame and the stator core. In step 2, the same contact stress as that in step 1 was derived using structural analysis through two-dimensional modeling of the frame and stator core without tolerances. The contact stress was calculated by applying the equivalent thermal expansion coefficient of the frame, and it was confirmed that the manufacturing tolerance and maximum stress intensity are linearly related. In step 3, electromagnetic analysis was performed at the rated operating point of the 2.2-kW induction motor using the model obtained in step 2. The magnetic flux density distribution of the stator core was derived via electromagnetic analysis and the iron loss, including the stress distribution, realized in step 2. The iron losses obtained under different conditions, including the stress of the stator core owing to the shrink fit tolerance, were compared, and the effectiveness of the shrink fit tolerance required to achieve a motor with high efficiency was evaluated.

In order to solve the leakage problem of the engineering mechanical hydraulic cylinder, a magnetorheological fluid (MRF) seal structure with a multistage source is designed. The magnetic f ield in the gap of the sealing structure is analyzed by ANSYS finite element analysis method, the influence about the number of magnetic sources and the length of pole teeth on the pressure capability of the MRF seal is studied, and the results are analyzed. The results show that the suitable number of magnetic sources is 10; The length of the pole teeth with the best magnetic concentrating effect is 0.7 mm. Then, the influence of the MRF injection volume, reciprocating speed, reciprocating distance and holding pressure time of the hydraulic cylinder on the MRF sealing pressure capability is studied. The experimental results show that the maximum pressure capacity can be achieved when the MRF injection volume is 12 ml. With the increase of reciprocating speed, the pressure capability of the MRF seal decreases obviously. With the increase of reciprocating distance and holding time, the sealing pressure capability has no obvious change. Through the finite element analysis and experimental study of the MRF seal, it is of great significance to develop a device with high sealing performance suitable for the hydraulic cylinders.

Ni-substituted Z-type hexaferrites with the chemical formula Sr₃Co_2-xNi_xFe₂₄O₄₁ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared by solid-state reaction processes. XRD analysis revealed that nearly a single Z-type hexaferrite phase could be obtained for the samples with Ni substitution x ≤ 0.5 when the samples were twice calcined at 1160 and 1235 ℃, respectively, in air. The complex permittivity (ε', ε") and permeability (μ', μ") spectra (100 MHz ≤ f ≤ 18 GHz) and electromagnetic (EM) wave absorption properties were studied on Sr₃Co_2-xNi_xFe₂₄O₄₁ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) powder-epoxy (10 wt%) composites. The permeability spectra continuously shifted to a lower frequency with an increase in x, owing to the decrease in the magnetocrystalline anisotropy. The peak frequency of μ" gradually decreased from 3.2 GHz to 2.0 GHz, and in turn, it shifted the corresponding EM absorption frequency range. The frequency corresponding to the minimum RL peak point also decreased from 3.3 GHz to 2.3 GH with an increase in x from 0 to 0.5. All the samples exhibited the lowest reflection loss of < -40 dB at the optimized frequency and thickness. The study shows that Ni substitution is very effective for the delicate tuning of electromagnetic absorption frequency in S-band (2-4 GHz).

Amorphous (Fe_xCo_1-x)₈₅B₅Zr_yNb_10-y (x = 0.6, 0.7, 0.8, or 0.9 and y = 7 or 8 at.%) ribbons were fabricated by the melt-spinning technique, and their thermal and magnetic properties were investigated. The results showed that all alloys had a fully amorphous structure, and the substitution of Zr for Nb resulted in high thermal stability and high saturation flux density (B_s) with fairly low coercivity (H_c < 21 A/m). Moreover, by varying the Fe/Co ratio, the optimum ratio with the highest B_s and low H_c was determined. As the Fe/Co ratio changed from 6:4 to 9:1, H_c decreased from approximately 20 to 9 A/m, and B_s also decreased gradually. A saturation flux density of 1.33 T was achieved with a coercivity of 9 A/m after optimization.

In many countries, the demand for motors has rapidly increased. For equipment automation and energy reduction, motors are efficient machines and play an important role in alleviating the current energy crisis. However, rotary machines have been studied instead of linear machines. Furthermore, tubular linear induction motors (TLIMs) have been developed for use in industry, but the characteristics of these machines have not been analyzed. In this study, using the finite element methodology (FEM), a TLIM was examined using the ratio of conductor thickness and back iron. The design of experiment (DOE) and response surface methodology were used to obtain this result. The TLIM is modeled to obtain thrust force in the steady state. Furthermore, conductor and back iron thickness are efficiently assigned using the DOE. The central composite design introduced in this study is used in various DOE methods. As a result, the conductor and back iron thickness ratio is obtained at an optimum value. This ratio can be used to design the TLIM for low voltages.

Binary alloy nanowires of Fe₃Co₇ system are synthesized in the highly ordered porous anodic aluminum oxide (PAA) templates by AC frequency (5, 50, 120, and 200 Hz) conversion electrodeposition method. High resolution field emission transmission electron microscope (HRTEM) and Lorenz TEM (LTEM) were used to study the morphology and the magnetic domain structure of the Fe₃Co₇ alloy nanowires, respectively. Magnetic measurements showed that the M-H curves presented a discontinuity in a restricted magnetic field, but with high squareness (about 90 %). Quantitative local measurements of the magnetic properties of the nanowires are explored by differential phase contrast (DPC) imaging. The magnetic properties, however, were significantly affected by the AC frequency, which is correlated with the specific magnetic structure formation of Bloch line. We reported herein a detailed investigation on Fe₃Co₇ alloy nanowires and their magnetic properties.

Magnetic hysteresis curves of cobalt ferrites with a fraction of cobalt being replaced by magnesium (Mg_xCo_1-xFe₂O₄) were investigated by vibrating sample magnetometry (VSM). The specimens with x ≤ 0.2 were prepared as thin films on silicon substrates by using a sol-gel deposition process. The VSM result revealed that the saturation magnetizations (M_S) of the Mg-substituted specimens were higher than that of CoFe₂O₄. The result of Raman spectral analysis suggested that the Mg-substituted specimens had higher tetrahedral Co²⁺ density in the spinel lattice compared to CoFe₂O₄. The increase in MS for Mg_xCo_1-xFe₂O₄ is ascribed to two reasons, the increase in tetrahedral Co²⁺ density and significant Mg²⁺ occupation in the tetrahedral sites.

The aim of this study was to investigate difference in brain metabolites between smokers and non-smokers in the brain insular region related to addiction for men in their twenties. Differences in brain connectivity between the two groups were also determined. A total of 20 males volunteers (10 smokers and 10 nonsmokers) were enrolled for this study. Magnetic resonance spectroscopy (MRS) was performed using a 3.0 Tesla MRI scanner. MRS data of left/right insular brain areas were acquired via point-resolved spectroscopy. A total of 3,096 functional magnetic resonance imaging (fMRI) images were obtained under axial conditions in 2D mode. Non-smokers showed significant differences in glycerophosphorylcholine, total choline, free creatine, and total creatine between left and right insular cortical regions. Differences in concentrations of metabolites in the islet cortex between smokers and non-smokers were higher in the left islet region than in the right insular region of non-smokers. Concentrations of tCr metabolites in the left insular area of non-smokers were higher than those of smokers. In addition, smokers showed higher connectivity in the right gyrus and occipital fusiform regions than non-smokers, whereas non-smokers had stronger connectivity between the left insular cortex area and the frontal role right than smokers. This study is meaningful in that it provides a new strategy using fMRI as well as MRS to identify differences in metabolism between smokers and non-smokers in a specific age group.

Newborns and premature infants generally undergo brain MRI tests under sedation and anesthesia. Sedation or anesthesia has a risk of side effects and may be contraindicated in newborns or premature infants with congenital diseases. Therefore, this study tested subjects by applying a self-sleep induction method. This study compared and analyzed a group (Group A), which tested 42 subjects using a sedation method (used chloral hydrate or Midazolam) for the brain MRI examination, and a group (Group B), which tested 84 subjects under self-sleep induction by applying a wrapping after feeding technique using a vacuum splint (MedVac). For image analysis, this study conducted SNR analysis between the two groups, calculated Cohen's Kappa coefficient to test the agreement between observers, and analyzed the examination time to evaluate the efficiency of the examination. The results of image analysis (SPSS independent sample t-test) were evaluated as T1 (p=0.101) and T2 (p=0.319), and the inter-observer agreement test (p=0.075) and statistical analysis of test time (p=0.160) were also statistically significant. There was no difference. Brain MRI through sleep induction is considered a safe and efficient test method.