At the boundary of two magnetic domains with distinct orientations, known as magnetic domain walls (DWs), a gradual spin rotation occurs due to the competing each magnetic energy within their internal structure. Devices utilizing these DWs have garnered significant interest across various applications as potential candidates for next-generation high-density information storage and logic devices. Furthermore, by investigating the formation and dynamic characteristics of these DWs, there are driving forces to enhance scientific understanding in physics, exploring the properties both static and dynamic aspects. This review article explores the principles and methods of measuring the DW velocity for understanding DW dynamics. The exploration covers various methods for inducing DW generation, followed by an elucidation of the fundamental measurement principles for observing DW velocity using electric transport and optical techniques. Recent advancements in the measurement of DW velocity are then discussed, considering diverse dynamic regimes (such as creep and flowing regimes) and the influence of driving forces (magnetic fields or currents).

The spintronic majority gate based on the current-induced magnetic domain wall motion is introduced. The spin majority gate is consisting of three individual domain wall input terminals and one output terminal after the logic operation. This simple structure can realize AND gate and OR gate. To realize NOT gate operation based on the magnetic domain wall motion a magnetic domain wall inverter, which can reverse the input domains is introduced as well. The physical origin of the magnetic domain wall inverter is so-called “the interlayer exchange coupling” or “Ruderman-Kittel-Kasuya-Yosida interaction”. Finally, the fabrication processes with several critical issues for the spintronic majority gates including the domain wall inverter are extensively discussed.

Spin structures are the unique magnetization configurations in the magnetic medium. Due to their intriguing physical properties, spin structures have attracted interest for development of the next-generation information storage/processing devices. The spin structures have been investigated in thin magnetic films where the magnetization distribution is uniform in the thickness direction. Recently, it has been revealed that, in bulk magnetic medium, the magnetization distribution is no longer uniform in the thickness direction, and it leads to novel physical properties distinguished from the physical properties of the spin structures in thin magnetic films. In this work, we review typical physical properties of spin structures such as high stability and rich dynamic properties. In addition, we briefly introduce the physical properties of spin structures, such as skyrmions and magnetic vortices, in bulk magnetic mediums, and novel 3D spin structures only stabilized in bulk magnetic mediums.

Novel nonvolatile devices like STT/SOT-based logic/memory/physical unclonable function (PUF), and FeFET have showed endless feasibility and technical viability of promising alternatives to CMOS devices, considering their ability to offer a solution for increased power dissipation in electronic circuits. As the STT/SOT-based devices are based on electron’s spin degree of freedom, they enable zero standby leakage, low power consumption, sustainable endurance, enhanced read/write performances. Especially, spin- based PUF has actively been developed using nonvolatility, and easy 3D integration capability with currently existing electronic circuits based on CMOS technology. In this work, recent research progress and challenges the spin-based PUF with ferromagnetic structures will be introduced for one example of advanced process and technology of novel nonvolatile devices and CMOS Co-integration.

In this review paper, we will show the research trends in spin torque oscillators, which have attracted much attention as nanoscale microwave generators. First, the fundamental of spin torque oscillators will be introduced, and then we will introduce several recent progress of spin torque oscillator for next generation neuromorphic devices. Specially, very interesting topic, ising machine based on spin torque oscillators will be briefly introduced.

In this paper, the magnetic field shielding effect of both the flux shunting shielding by ferromagnetic materials and the induced current shielding by conductors are analyzed for a spherical shell structure in the low frequency range. The shielding ratio equations are derived theoretically from Maxwell’s equations and the results are compared with the ones from electromagnetic field simulations. For the shell layer and materials, a single-layer shell of ferromagnetic material, a single-layer shell of conductor, and a double-layer shell of ferromagnetic material and conductor are considered. For the double-layer shell, a model with an inner conductor layer and one with an outer conductor layer are analyzed separately. Also, material properties and layer thickness requirements are presented that are needed for the specific shielding effectiveness.

This study presents the comparison of the electromagnetic, operating, and mechanical characteristic analysis according to the rotor structure of the MW-class permanent magnet synchronous motors for electric propulsion ships. Electromagnetic and mechanical characteristic analyses are performed under the same constraints and requirements for surface mounted, Bar type interior, V type interior permanent magnet synchronous machines. Based on the analysis results, a rotor structure of a permanent magnet synchronous motor suitable for electric propulsion ships is proposed.