The electronic structure of Mn_3-xCo_xGa (x = 0.56) film, which is a candidate material for a half-metallic ferrimagnet, has been investigated by employing soft X-ray absorption spectroscopy (XAS), soft X-ray magnetic dichroism (XMCD), and photoemission spectroscopy (PES). According to Mn and Co 2p XAS measurements, Mn ions are divalent and have covalent bonding, while most of the substituted Co ions are in metallic states. The Co 2p XMCD spectrum of Mn_3-xCo_xGa (x = 0.56) film is very similar to that of Co metal, supporting the finding of Co 2p XAS. Finite XMCD signals are found in both Co and Mn 2p XMCD spectra, but the intensity of the Mn 2p XMCD is much weaker than that of Co 2p XMCD. XMCD measurements reveal that the substituted Co ions in Mn_3-xCo_xGa (x = 0.56) form ferromagnetic metallic clusters and induce weak polarization in Mn ions. Hence, this study suggests that ferromagnetic metallic Co clusters play an important role in determining the magnetic properties of Mn_3-xCo_xGa (x = 0.56) films.

In this paper, the magnetic field of the domestic induction cooktop is measured according to the IEC standard and the values are compared with exposure limits in the international EMF (Electromagnetic Field) safety guidelines. Also, the equivalent coil of the induction cooktop is derived based on the measured magnetic field distribution using the magnetic dipole moment equation. The magnetic field by the equivalent coil is greater than the measured values at all distances considered and the conservative exposure assessment of the basic restrictions is possible. Next, the current density induced in the human model by the equivalent coil is calculated using the simulation software at various distances for the exposure assessment of the EMF basic restrictions. The exposure index of the induced current density with respect to the exposure limit in the ICNIRP (International Commission on Non-Ionizing Radiation Protection) 1998 guideline was less than 0.369 for all the cases considered.

This paper presents the design and analysis of a Voice Coil Motor (VCM) for vehicle Eco-Pedal system. To prevent the excessive gas consumption for f uel-efficient vehicle the e lectric actuator produces a counter force to the vehicle’s pedal to be pressed stiffly. Major performances of the VCM are required such as a high force density and a low detent force. The VCM requires a 3D finite element analysis, on the other hand, the VCM has an axial symmetry structure, so it is possible to use a equivalent 2D axisymetric analysis. In this paper, the analysis and design technique of the VCM thrust is based on the 2D axisymetric analysis and the design and analysis results are verified with experimental results.

In this paper, a torque damage equation due to the insulation aging of stator windings is proposed to predict the lifetime of a permanent magnet synchronous motor for operating temperature and use time. An insulation resistance equation for the motor is induced to replicate the winding deterioration of a stator under the given operating condition, and then an influence of insulation aging on torque performance of the motor is analyzed by means of an electromagnetic simulation tool. Based on numerical results, a torque damage equation is deduced to establish the relationship between insulation aging and torque deterioration according to the operating temperature and time of the motor. Finally, it is applied to an interior permanent magnet synchronous motor, and the lifetime limit of the motor is estimated for a certain operating temperature.

We study ferromagnetic resonance (FMR) properties of topological insulator Bi₂Se₃ and ferromagnet NiFe (permalloy) multilayer structures. We found that Bi₂Se₃/NiFe shows two times larger magnetic damping than that of single NiFe, which indicates strong spin pumping exists in the interface between Bi₂Se₃ and NiFe. Also, 1 nm thick MgO layer was inserted into between Bi₂Se₃ and NiFe, where spin-pumping is expected to be suppressed. Bi₂Se₃/MgO/NiFe shows same amount of spin-pumping effect as observed in Bi₂Se₃/NiFe, while thin MgO layer can be beneficial for suppressing the formation of magnetic dead layer. These results show that 1 nm thick MgO can be utilized as a good spacer layer without a loss of spin-pumping in the multilayer structures with topological insulator.

SWE-SMs (Slipring-less Winding Excited Synchronous Machines) have low price and sturdy rotor structure, and there are ongoing researches to use them for the drive units of EVs (electric vehicles) and e-Mobility. In this paper, the multi-objective optimization of an SWE-SM is investigated in order to improve its torque characteristics. The torque and back EMF (electromotive force) of an SWE-SM are calculated and analyzed using finite element simulations and Arkkio’s method considering nonlinear B-H curve of the core. In order to increase the average torque and decrease the cogging torque at the same time, the multi-objective optimization of SWE-SM is performed using the weighted sum method. Various ratios of the weighting factors of the multi-objective function are tested and the optimal solutions are analyzed to check the uniformity of the Pareto optimal points. The results show that the average torque and the cogging torque of an SWE-SM can be optimized effectively by adjusting the ratio of the weighting factors according to the preference set by the designer.

This paper presents an electromagnetic analysis technique for an interior permanent magnet synchronous machine (IPMSM) based on the improved subdomain method. Analytical solutions are derived by considering the permeability of the bridge, back yoke, and pole-piece regions of the rotor and slot-opening and slot structure in the stator. Based on analytical solutions, electromagnetic performances such as flux density, flux linkage, back-EMF and electromagnetic torque are calculated. The validity and improvement of the proposed method are verified through comparison with the finite element results. The proposed analysis method can be used in various ways, such as electromagnetic characteristic analysis, initial design, and optimal design by considering the saturation characteristic of the iron core.

In this study, we experimentally observed the domain wall creep motions under the magnetic field in the ferromagnetic Co/Ni/Co magnetic wires with or without antiferromagnetic IrMn layer, respectively, using a magento-optical Kerr microscope system capable of real-time magnetic domain observation. As a result of the observation, it was found that the strength of the magnetic field required to move the magnetic domain wall was larger in the sample with the IrMn layer than the sample without the IrMn layer, and also, it was increased as the wire width decreased. In addition, we found that the magnetic domain wall speed characteristics according to the strength of the magnetic field in the two samples were well explained by the thermally activated model assuming the domain wall creep motion.

Magnetic hyperthermia, which is possible in local therapy, using magnetic nanoparticles (MNPs) and alternating magnetic field (AMF), is a cancer therapy among various treatments. In general, hyperthermia therapy is a type of treatment in which a cancer cell is exposed to high temperatures exceeding 42 ℃ to kill the cancer cell. This method is relatively lower side effects when compared to surgical surgery, radiation therapy, and chemotherapy. In this paper, we introduced a hyperthermia mechanism using MNPs, the relationship between the mechanisms and MNPs, and methods for magnetic hyperthermia. Typically, hyperthermia is divided into three parts: local, regional, and whole-body. In recent studies, actively targeted and controlled hyperthermia technology, which can use all three methods, has been reported.