The gyromagnetic effect, i.e. one of the most significant discoveries in physics, is associated with a mutual conversion of angular momentum between macroscopic mechanical rotation and microscopic electron spin. The gyromagnetic field produced by a feasible mechanical rotor is, however, too small for practical applications. Surface acoustic wave is a promising candidate to improve the gyromagnetic effect because an elliptical oscillation of lattice with a frequency of GHz order can be realized. Here, experimental demonstrations on a gyromagnetic spinwave excitation and its reciprocal effect, i.e. a phase shift of the acoustic wave, are presented. Furthermore, we also show that the gradient of the acoustic gyromagnetic field can produce an alternating spin current, whose amplitude is increased nonlinearly with the frequency.

In order to solve the thermal problem of SiC-based automotive inverters with high heat generation of 500 W/cm², the boiling surfaces composed of a lotus copper joined to a grooved surface is developed. The critical heat flux and the maximum heat transfer coefficient of boiling surfaces are the highest 534 W/cm² and 115 kW/(m² •K) in the case of water.The boiling surface is expected to be applied not only to the cooling for automotive inverters but also to the cooling for server-system.

Topological materials exhibiting giant magnetic responses have attracted a great deal of attention as a new material resource for magnetic sensors. By fabricating amorphous thin films of ferromagnetic Fe-Sn alloy that was inspired by a topological ferromagnet Fe₃Sn₂, the authors developed a Hall sensor based on large anomalous Hall effect of the Fe-Sn films. Furthermore, by combining the anisotropic and unidirectional magnetoresistance effects, three-dimensional magnetic-field sensing in a simple planar-type device configuration was demonstrated. This article overviews principles of thin-film magnetic sensors and introduces the synthesis of Fe-Sn amorphous films and the characteristics of the anomalous Hall effect-type Hall sensor and three-dimensional magnetic-field sensing device.

Nickel oxide (NiO) is a wide bandgap oxide semiconductor and functional material because it exhibits p-type conductivity, high absorption coefficient, and relatively low ionization potential. Therefore, it is a promising candidate in novel applications including “invisible” solar cells, sensors, transistors, and hole-injection layers. In this paper, the fundamental properties of NiO thin films deposited by conventional RF magnetron sputtering, as well as various visible-light transparent devices using NiO such as solar cells, IoT monolithic gas sensors, and “self-powered devices” are introduced. Moreover, the robustness of devices that use NiO, such as radiation resistance, is also mentioned.

Metal halide perovskites are promising solution-processable semiconductors with unique optical, transport, and spin-related properties. Here, we report our recent work on the nonlinear optical properties of halide perovskite semiconductors and discuss their electronic structures and high-order harmonic generation processes under extremely intense laser excitation.

Intensive research is being conducted to further improve the performance of lithium-ion secondary batteries. Conventional cathode materials exhibit excellent charge-discharge cycle characteristics because only Li ions are extracted and inserted while maintaining the crystalline structure of the material. On the other hand, lithium-rich layered oxide (LLO) materials with high energy density have achieved extraction/insertion of a large amount of Li ions with a low crystalline structure. This paper introduces an example of research that clarified the existence of a low-crystal structure in LLO formed by the crystal structure change accompanying the migration of pillar metal ions that support the Li deficient layer during extraction of Li-ions revealed by a pair distribution function analysis.

Surface analysis requires the comprehensive knowledge and experience of analysts in sample treatment and data analysis in order to analyze the microstructure and chemical composition of a sample in a wide range of depth from the atomic layer to the micrometer. Therefore, the surface analysis is one of the most difficult techniques to automate the data analysis. To overcome this difficulty and automate data analysis, it is important to reveal the tacit experience of skilled analysts through a data-driven approach. In this basic course, we will introduce an example of automation of data analysis using a data-driven approach for X-ray photoelectron spectroscopy as one of the surface analysis methods.