We report the experimental observation of the domain wall creep motion in the ferromagnetic CoNi multilayers interfacing with antiferromagnetic IrMn layer, using a magento-optical Kerr microscope system capable of direct observation of domain change. From the magnetic domain images observed in real time, it can be seen that as the IrMn thickness increases from 0 Å to 25 Å, the strength of the magnetic field required to move the magnetic domain wall gradually increases, due to an increase in coercivity due to the exchange bias effect at the interface. In addition, it was found that the magnetic domain wall velocity characteristics according to the magnetic field in all samples were well explained by the thermal activated model assuming the domain wall creep motion.

Alloys of rare earth metal and transition metal with ThMn₁₂ structure are expected to have high saturation magnetization and high magnetic anisotropy. Despite its advantages, it has not been commercialized because of its metastability. GdFe₁₂ is a material having ThMn₁₂ structure. Therefore, it is expected to be difficult to stabilize GdFe₁₂ in bulk form. In this study, GdFe₁₂ was fabricated in the form of epitaxial thin films to stabilize the phase. The films were grown epitaxially from 500 ℃ to 200 ℃. From the results of x-ray diffraction and x-ray absorption, it was confirmed that a (330) GdFe₁₂ thin films were grown. The epitaxial GdFe₁₂ thin film had a saturation magnetization (M_s) = 1130 emu/cm³ and coercivity = 712 Oe at a deposition temperature of 400 ℃.

Recently, pure Ni powder, used as conductive powder material for semiconductor test sockets, has disadvantage of decreasing the life cycle of test sockets because of its low hardness (Hv = 100). This study was carried out composition design of the Ni-(0.1~30)wt%X binary alloys and the Ni-3wt%Fe-0.3wt%X ternary alloys, ingot manufacturing, heat treatment, polishing, microstructure observation and characteristic evaluation to develop new Fe-based Electric Conductivity alloy with excellent hardness to replace pure nickel powder. As a result, although the Ni-5wt%Co(Fe) binary alloys with Co and Fe elements is more conductive and magnetic than other alloys, in order to improve hardness, it was found that the adding B and C element is more effective. Meanwhile, it was found that the electrical resistance of alloys depended on Matthiessen's rules and mixing rules, the magnetism of alloys is enhanced in proportion to the increase addition of Co and Fe elements. Furthermore, the hardness was found that the presence of solid solution (or intermetallic compound) according to the chemical composition of the alloy, and the precipitation hardening caused by heat treatment were combined.

We analyzed the thickness dependence of eddy current (EC) signals measured using a AMR based EC sensor in ferromagnetic SM20C carbon steel plate. The high frequency EC signals showed nearly constant value with thickness. While in the low frequency EC signals, the amplitude was exponentially decreased and the phase was linearly increased, respectively. The phase of EC signals was more sensitive than the amplitude of EC signals with thickness of carbon steel plate. Thus the phase of low frequency EC signals can be applied for the thickness measurement of ferromagnetic carbon steel plate.

In recent, most mobile devices such as smartphone come with embedded 3-axis magnetic sensor. The 3-components of earth magnetic field for the body axis of devices are essential to determine the orientation of the devices together with the 3-components of earth gravitational field. In this paper, we present in detail the algebraic process deriving the formulas to calculate the Yaw, Roll and Pitch angles, which specify the orientation of mobile devices, from the measured total 6-components of earth magnetic and gravitational fields. In addition, the derived formulas are verified by experiment with a simple apparatus and smartphone. Through this paper, we expect to provide a reference to developers of application software and sensor firmware who require calculating the orientation angles of mobile devices.

The solenoid coil is one of the most important design component for efficient electrical energy conversion in the structure of electric machines such as motors, generators, and transformers. When the current is applied to a multi-turn solenoid coil, a uniform magnetic field which is proportional to the number of coil windings is generated inside the coil, and the high-density magnetic field generated by the coil can be converted into mechanical kinetic energy by applying the strong electromagnetic force to a ferromagnetic object. However, the interaction between the current and magnetic field of the solenoid coil generates a strong electromagnetic force between each coil wire. In this paper, when the current flows in the multi-turn solenoid coil, the analysis method and numerical equation for calculating the electromagnetic expansion force generated in the radial direction of a multi-turn solenoid coil are proposed. Calculated results are verified by simulated ones.

In the field of small and medium-sized electric motors, cost is emphasized rather than performance and efficiency. A single-phase or TPSRM (two phase SRM) has been studied because of economic aspect, and in particular, various magnetic structures have been developed for TPSRM, which has a high output density and can be self-starting by changing the magnetic structure. Among them, the E-core TPSRM has the advantage of saving the stator core and having a short magnetic path and no alternating magnetic flux in the stator. In this paper, the improved magnetic structure of E-core TPSRM is presented and analyzed. Compared to the conventional E-core TPSRM, the number of rotor poles is smaller, therefore, the switching frequency per a phase is smaller, and it has the advantage of reducing switching loss and core loss.

In computed tomography, X-ray attenuation occurs by various organs that make up the human body. The attenuated data is used to create an image that we can observe with our eyes. In the process, the patient is exposed to radiation that cannot be avoided. Recent research is trying to improve the image quality while reducing the radiation exposure dose to the human body. Therefore, reconstruction algorithms of various methods are newly introduced. In the future, along with the development of a reconstruction algorithm, it is expected that the development of a detector that realizes an image of excellent quality with a small dose is expected.

Computed tomography is highly evaluated for its diagnostic excellence through rapid technological progress. Among them, coronary CT, which diagnoses heart disease, is helping to keep the golden time of heart disease treatment. Recently, dual-energy CT, which is widely used in heart and uric acid stones, not only increases the usefulness of the examination, but also decreases the patient's exposure dose. In the future, multi-energy computed tomography is expected to expand the development of new technologies such as photon counting detector, fusion with 3D printing technology, machine learning analysis in medical imaging, and introduction of artificial intelligence technology.