The iron compounds in minerals of obsidians from the continental Far East, Mount Baekdu near the Sino-Korean border, Kyushu in southwest Japan, and Shirataki, Japan were analyzed using ⁵⁷Fe Mössbauer spectroscopy. The mineral Pyroxene (FeSiO₃) in obsidian was found in the metamorphic rocks of Mount Beakdusan, Kyushu, and Hokkaido. However, the mineral biotite in obsidian was found in Kyushu only. The main phases of the Hokkaido obsidians are olivine, pyroxene, magnetite, and nano-oxide. Some Hokkaido obsidian showed the presence of hematite. In obsidians, iron species are mostly hosted by divalentions of olivine and pyroxene. In mineralogical and geochemical studies on obsidian from the continental Far East, the origination of the magma compositions and the crystallization environments were confirmed to have been different.

Fe-N/C electrocatalysts was synthesized using electron beam (e-beam) irradiation to improve the oxygen reduction reaction activity in the polymer electrolyte membrane fuel cells. After synthesizing, the characteristics of catalyst before and after acid washing treatment were measured in the rotating disk electrode (RDE). It was confirmed that the catalyst was successfully synthesized measured using TEM, XRD, and Mössbauer spectroscopy. However, the formation of some impurities, such as oxides, were also confirmed. The electrochemical properties during oxygen reduction reaction (ORR) was enhanced after the acidic washing treatment of the catalyst.

In recent years, the synthesis and characteristics of nanoparticles have significantly advanced, leading to a growing interest in researchers studying new magnetic nanoparticles in various application fields. Hyperthermia is a method that utilizes magnetic nanoparticles to inject into cancer cells and utilizes the heat generated by the magnetic nanoparticles under an alternating magnetic field to destroy the cancer cells. To achieve this purpose, magnetic nanoparticles with almost zero coercivity and characteristics of superparamagnetism or single-domain ferri- or ferromagnetism and minimal size are required. This review paper is based on the Mössbauer spectroscopy technique to observe magnetic nanoparticles at the nano-scale. It focuses on the research of heat generation and magnetic properties of various forms of magnetic nanoparticles and introduces the research trends of magnetic nanoparticles that can potentially be applied in hyperthermia.

In this study, the magnetization reversal change according to the change in the thickness of the Ni upper layer was observed in the Co/Ni multilayer thin film, using a magneto-optic Kerr magnetometer capable of measuring the magnetic hysteresis curve and the magnetic viscosity curve while adjusting the direction of the magnetic field. First, as a result of measuring the hysteresis curve, the magnetization reversal of the sample showed a tendency to move the domain wall, and it was found that the magnitude of the coercive force increased as the thickness of the Ni upper layer changed from 7.5 Å to 12.5 Å. In addition, as a result of measuring the magnetic viscosity curve according to the size of the magnetic field, it was found that the magnetization reversal behaviors of all samples were well explained by the thermal activation model, and the thermal activation volume decreased as the thickness of the Ni upper layer increased from 7.5 Å to 12.5 Å.

We carried out the systematic study for bi-layer structures composed of ferromagnetic NiFe and heavy metal W by using a ferromagnetic resonance (FMR) measurement based on a coplanar waveguide (CPW). Different thick tungsten (W) layers (4, 6, 8, and 10 nm) were deposited on 10 nm thick permalloy (NiFe), respectively, and the magnetic damping and effective magnetization values of each sample were compared. In addition, the temperature-dependent ferromagnetic resonance measurement were also measured at the range of 4~300 K. FMR results of each sample at both 10 and 300 K don’t show significant variations in magnetic damping and effective magnetization values with respect to the thickness of the W layer. For the NiFe 10 nm/W 4 nm sample, we examined the magnetic damping and effective magnetization values as a function of temperature, revealing a slight increase in both values as the temperature decreased. In this study, the established FMR equipment for magnetization dynamics will bring the groundwork for systematic investigations about the effective magnetization and magnetic damping under various conditions.