記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Interactions  

X-ray powder diffraction, magnetization, and 57Fe Mössbauer spectroscopy measurements were performed to investigate the effects of heat treatment on the magnetic properties of MnFeGe with hexagonal Ni2In-type structure. The samples were annealed at 1173 K for 24 h, as a solution treatment (ST), and then aged at 1073 K (AG-1073 K), 973 K (AG-973 K) and 773 K (AG-773 K). Curie temperature was the highest at AG-1073 K (201 K), and the lowest at AG-773 K (169 K). In ST and AG-1073 K, Mössbauer spectrum was represented by three subspectra. In AG-1073 K, 19% of the Fe atoms occupied 2a-site and 71% of the Fe atoms occupied 2d-site. The hyperfine fields of 2a- and 2d-sites at 15 K were 20.3 T and 9.99 T, respectively. Approximately 10% of the iron atoms contributed to the subspectrum of nonmagnetic phase. On the other hand, to represent the spectra obtained at 15 K for samples annealed at lower temperatures (AG-973 K and AG-773 K), an additional subspectrum with the hyperfine field of 21.6–22.0 T was required, which was due to the ferromagnetic impurity phase. The obtained results showed that as the aging temperature decreased, Fe occupying the 2a-site with a large hyperfine field decreased, resulting in a decrease in the macroscopic magnetic properties of MnFeGe.

DOI： 10.1007/s10751-024-01951-9

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掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.38.011136

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.7566/JPSCP.38.011138

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.7566/JPSCP.38.011139

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Magnetism and Magnetic Materials  

Site occupation of Fe atoms, magnetic and structural properties in MnCo1-xFexGe (x = 0.2, 0.5, 0.7 and 1.0) were investigated. Two phase co-existence of the hexagonal Ni2In-type structure (P-phase) and the orthorhombic TiNiSi-type structure was observed at room temperature for x = 0.2. For x = 0.5, 0.7 and 1.0, MnCo1-xFexGe was confirmed to be the P-phase. With increasing x from 0.2 to 1.0 for the P-phase, the lattice parameter ap slightly increased by only 0.14%, but cp decreased by 2.1%. As a result, when x was increased from 0.2 to 1.0, the unit cell volume of the P-phase decreased monotonously by 1.8%. The saturation magnetic moment and Curie temperature of MnCo0.5Fe0.5Ge were 2.16 μB/f.u. and 205 K, respectively, which decreased monotonically with increasing x. 57Fe Mössbauer spectroscopy indicated that 90–94% of the substituted Fe atoms occupied the Co-site but 10–6% of the Fe also occupied the Mn-site in the P-phase. For x = 0.5, 0.7 and 1.0, the hyperfine field at the Co-site was 8.29–9.44 T, which was larger than that at the Mn-site. The sign of quadruple splitting at the Co-sites changed from positive to negative with the increase of x, suggesting that the electric field gradients at Co-sites changed.

DOI： 10.1016/j.jmmm.2022.170000

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Magnetism and Magnetic Materials  

In this study, the Sm2Fe17 powder was subjected to nitridation at 743 K under N2 pressures of 0.05 and 0.1 MPa to investigate the growth kinetics of Sm–Fe–N. Two-phase growth of the fully nitride (FN) Sm2Fe17N3 phase and the nitrogen-poor (NP) Sm2Fe17Nx phase (0 < x < 3; x denotes the nitrogen content) was observed using 57Fe Mössbauer spectroscopy. Although the x value was greater at 0.05 MPa than at 0.1 MPa in the early stage of nitridation, the opposite trend was observed in the later stage. At a nitrogenation time of 24 h, nitridation was nearly complete at 0.1 MPa, while x tended to saturate and did not reach 3 at 0.05 MPa. The nitridation process was discussed based on two simultaneous growth processes: (i) the diffusion of the nitrogen atom in the NP phase and (ii) the nucleation and growth of the FN phase. A process combining N2 pressure and nitrogenation, which facilitated nitrogenation under low N2 pressure and high N2 pressure at the beginning and end of the nitridation process, respectively, achieved faster nitridation than process with a single N2 pressure.

DOI： 10.1016/j.jmmm.2022.169295

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人 日本鉄鋼協会  

Tramp elements in steel, such as Cu and Sn, cannot be removed by acid treatment. Since these elements condense by repeating recycling process, leading to deterioration of strength. Therefore, the methods for avoiding condensation or removing tramp elements are required. In this study, in-magnetic-field annealing process was focused on because magnetic field is effective for diffusion, phase transformation, phase diagram and precipitation. In-magnetic-field annealing of Fe-1mass%Cu at 773 K was performed in 5 and 10 T for investigating precipitation behavior of supersaturated Cu. From microstructural observation, precipitation of Cu-rich phase in Fe-matrix, and magnetic field effect on itself were not observed clearly. Increase of the hyperfine field was detected for the samples annealed at 5 T by Mössbauer spectroscopy, indicating the enhancement of the Cu-precipitation. On the contrary, hyperfine field for 10T-annealed sample was slightly smaller than that for 0 T. Therefore, in-field annealing effect on Cu-precipitation became unclear at 10 T. These magnetic field effects were discussed in the viewpoints of the change of Cu–Fe phase diagram and the atomic diffusion under magnetic field. Difference of the magnetic field effects on precipitation between 5 T and 10 T is explained by the competition between the enhancement of the driving force of the precipitation and suppression of the atomic diffusion. The obtained results indicated that there is optimized magnetic field intensity for controlling Cu-precipitation.

DOI： 10.2355/isijinternational.isijint-2021-404

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CiNii Research

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記述言語：日本語   掲載種別：論文集(書籍)内論文   出版者・発行元：Materials Science Forum  

The change in the positron annihilation lifetime (PAL) of vacancy clusters before and after electrolysis hydrogen charging was determined using PAL measurements in electron-irradiated F82H. The experimental change indicated 8 hydrogen atoms were trapped in vacancy clusters; whereas the theoretical calculation resulted in approximately 14 atoms. As the samples were left at room temperature for 5 min until the start of the PAL measurements, the de-trapping effect of hydrogen atoms was also considered; approximately 13 hydrogen atoms were captured at each vacancy cluster. The PAL decreased after annealing at 148 K, which could not be explained theoretically. Therefore, further experiments and discussions are needed to obtain a precise change in the PAL of vacancy clusters containing hydrogen atoms in F82H.

DOI： 10.4028/www.scientific.net/MSF.1024.71

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開催年月日： 2023年10月

記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（指名）  

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開催年月日： 2022年8月

記述言語：英語   会議種別：ポスター発表  

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記述言語：日本語  

記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（指名）  

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