研究者詳細 - 小山　佳一

論文 - 小山　佳一

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Sueyoshi Y., Kobayashi R., Mitsui Y., Koyama K. . Liquid–Solid Reaction of MnBi Phase in Bi/Mn Diffusion Couples under a Magnetic Field . Journal of Electronic Materials54 ( 7 ) 5137 - 5142 2025年7月

記述言語：日本語出版者・発行元：Journal of Electronic Materials

The influence of a 5 T magnetic field on the liquid–solid reaction of ferromagnetic MnBi phase at 573 K was investigated using Bi/Mn diffusion couples. A MnBi phase layer was not formed but MnBi grains were observed at the Bi/Mn interface. Because of the formation of MnBi grains, concavities were observed on the Mn surface. At 0 T, the concavities expanded with increasing annealing time. The magnetic field increased the number of nucleation sites of the MnBi phase, which also increased the number of concavities at the Mn surface. The MnBi grains synthesized at 0 T were isotropic and randomly oriented, while the MnBi grains at 5 T were elongated along the c-axis and oriented parallel to the magnetic field direction. The in-field reaction enhanced the number of nucleation sites of MnBi phase and oriented the elongated MnBi grains.

DOI： 10.1007/s11664-025-11985-6

Mitsui Y., Watanabe Y., Kobayashi R., Takahashi K., Koyama K. . Effects of Magnetic Field Intensity on the Reaction in Mn/Ga Diffusion Couple . Journal of Electronic Materials54 ( 7 ) 5130 - 5136 2025年7月

記述言語：日本語出版者・発行元：Journal of Electronic Materials

The applied magnetic field intensity and the magnetic state of the reacted phase are important factors for in-magnetic-field phase growth. In this study, the in-magnetic-field reaction in Mn/Ga diffusion couples was analyzed under applied magnetic fields of up to 15 T at 573 K and 773 K. It was found that the growth rates of the Ga-rich phases (λMnGa and Mn<inf>2</inf>Ga<inf>5</inf> phases) showed different behavior with respect to the magnetic field intensity when the Mn-rich phases (Mn<inf>3</inf>Ga and γMnGa phases) were ferromagnetic at 573 K and paramagnetic at 773 K. At 573 K, the thicknesses of the Ga-rich phases at 5 T became thinner than the same phases at 0 T, and further decreased asymptotically under a higher magnetic field of 15 T. The thicknesses of the Mn-rich phases were independent of the magnetic field intensity. At 773 K, the thicknesses of the Ga-rich phases in a 10 T-annealed sample were reduced to 45–55% of the corresponding thicknesses in a 5 T-annealed sample. These behaviors were explained based on the contribution of the Zeeman energy to the formation enthalpy of the Mn-Ga phases in the ferromagnetic and paramagnetic regions.

DOI： 10.1007/s11664-025-11898-4

Mitsui Y., Fumoto S., Kobayashi R., Takahashi K., Koyama K. . High Magnetic Field Effects on Phase Transformation Kinetics of ε-Mn-Al Probed Using Differential Thermal Analysis . MATERIALS TRANSACTIONS66 ( 2 ) 230 - 235 2025年2月査読

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本金属学会

Differential thermal analysis (DTA) on quenched Mn55Al45 with hcp structure (ε-phase) was performed under magnetic fields up to 15 T in order to investigate the magnetic field effects on the transformation kinetics of ε-phase. So far, the annealing of ε-phase under magnetic field indicated the acceleration of the phase transformation from the ε-phase to the metastable ferromagnetic τ-phase with L10 structure and the suppression of the decomposition into the equilibrium phase (β-phase). In this study, as the magnetic field intensity increased, the transformation temperature from ε-phase gradually decreased to the lowest value in the range from 0 to 4 T. A single exothermic peak was observed on each DTA curve, and it was found that the peak contained plural exothermic ε–τ and τ–β transformations. Activation energy of the transformation also showed the lowest value in the magnetic field range from 4 to 10 T, suggesting that the activation energy of the ε–τ transformation decreases at low magnetic field region from 0 to 4 T and the activation energy of the τ–β transformation increases at high magnetic field region from 10 to 15 T. These changes in activation energy were discussed by contribution of Zeeman energy for nucleation of the τ-phase in the ε-matrix and that of β-phase from the τ-phase. [doi:10.2320/matertrans.MT-M2024129]

DOI： 10.2320/matertrans.mt-m2024129

Sueyoshi Y., Kobayashi R., Onoue M., Mitsui Y., Umetsu R.Y., Koyama K. . Structural and Magnetic Properties of MnCo<sub>1-</sub><i><sub>x</sub></i>Fe<i><sub>x</sub></i>Ge<sub>1-</sub><i><sub>y</sub></i>Si<i><sub>y</sub></i> (<i>x</i>, <i>y</i> = 0, 0.5) . MATERIALS TRANSACTIONSadvpub ( 0 ) 758 - 763 2025年査読

記述言語：英語出版者・発行元：公益社団法人日本金属学会

Magnetic and structural properties of MnCo<inf>1−x</inf>FexGe<inf>1−y</inf>Siy (x, y = 0, 0.5) were investigated using X-ray powder diffraction and magnetization measurements in the temperature (T) range from 5 to 370 K and in magnetic fields up to μ<inf>0</inf>H = 5 T. At room temperature, MnCoGe and MnCoGe<inf>0.5</inf>Si<inf>0.5</inf> were the orthorhombic crystal structure (M-phase), MnCo<inf>0.5</inf>Fe<inf>0.5</inf>Ge was the hexagonal crystal structure (P-phase), and MnCo0.5Fe0.5Ge0.5Si0.5 had two-phase coexistence of the M- and P-phases. MnCoGe and MnCo<inf>0.5</inf>Fe<inf>0.5</inf>Ge were a simple ferromagnetic and their Curie temperatures (TC) were determined to be 340 K and 200 K, respectively. MnCoGe<inf>0.5</inf>Si<inf>0.5</inf> and MnCo<inf>0.5</inf>Fe<inf>0.5</inf>Ge<inf>0.5</inf>Si<inf>0.5</inf> in μ0H ≤ 1 T showed a gentle dip in thermomagnetic curves at 10 ≤ T ≤ 100 K below TC which disappears when a magnetic field of μ0H > 3 T was applied. The magnetization curves of MnCoGe<inf>0.5</inf>Si<inf>0.5</inf> and MnCo<inf>0.5</inf>Fe<inf>0.5</inf>Ge<inf>0.5</inf>Si<inf>0.5</inf> at 5 K exhibited that a metamagnetic transition with the magnetic hysteresis in 0 < μ<inf>0</inf>H < 3 T. Our results suggest that substituting Fe for Co in MnCoGe system weakens the ferromagnetic interaction, whereas substituting Si for Ge strengthens the antiferromagnetic interaction.

DOI： 10.2320/matertrans.mt-mbw2024001

Kobayashi R., Fumoto S., Mitsui Y., Takahashi K., Koyama K. . Differential Thermal Analysis of Ferromagnetic Mn55Al45C2 and Mn53Zn2Al45 Under High Magnetic Fields . Journal of Electronic Materials 2025年

記述言語：日本語出版者・発行元：Journal of Electronic Materials

Magnetic field effects on the activation energy, E<inf>a</inf>, of phase transformation in the hcp phase of Mn<inf>55</inf>Al<inf>45</inf>C<inf>2</inf> and Mn<inf>53</inf>Zn<inf>2</inf>Al<inf>45</inf> were investigated by differential thermal analysis (DTA) under high magnetic fields up to 10 T. Single exothermic peak including plural transformations was observed for both Mn<inf>55</inf>Al<inf>45</inf>C<inf>2</inf> and Mn<inf>53</inf>Zn<inf>2</inf>Al<inf>45</inf>. No systematic magnetic field dependence of transformation temperature was observed for either Mn<inf>55</inf>Al<inf>45</inf>C<inf>2</inf> or Mn<inf>53</inf>Zn<inf>2</inf>Al<inf>45</inf>. E<inf>a</inf> for Mn<inf>55</inf>Al<inf>45</inf>C<inf>2</inf> and Mn<inf>53</inf>Zn<inf>2</inf>Al<inf>45</inf> under magnetic fields showing different behavior. E<inf>a</inf> for Mn<inf>55</inf>Al<inf>45</inf>C<inf>2</inf> monotonically increased with increasing magnetic field intensity, whereas E<inf>a</inf> for Mn<inf>53</inf>Zn<inf>2</inf>Al<inf>45</inf> had a minimum value at 5 T. These magnetic field effects on E<inf>a</inf> have been discussed by dividing the reduction effect of E<inf>a</inf> (transformation to ferromagnetic phase) in the lower magnetic field region and the enhancement effect of E<inf>a</inf> (transformation from ferromagnetic phase) in the higher magnetic field region.

DOI： 10.1007/s11664-025-12057-5

Onoue M., Mitsui Y., Kobayashi R., Umetsu R.Y., Uwatoko Y., Koyama K. . Magnetic field effect on decomposition of Sm2Fe17N3 probed using 57Fe Mössbauer spectroscopy . Interactions245 ( 1 ) 2024年12月

記述言語：日本語出版者・発行元：Interactions

In order to clarify the influence of the magnetic field on the thermal decomposition of Sm<inf>2</inf>Fe<inf>17</inf>N<inf>3</inf> powder, we conducted a heat-treatment (HT) experiment in a vacuum of 38 Pa, at a temperature of 723 K, and in a magnetic field of zero and 5 T. Results of X-ray diffraction measurement, temperature dependence of magnetization and <sup>57</sup>Fe Mössbauer spectroscopy experiments showed that fully-nitride Sm<inf>2</inf>Fe<inf>17</inf>N<inf>3</inf> decomposes to nitrogen-poor Sm<inf>2</inf>Fe<inf>17</inf>N<inf>x</inf> (0 < x < 3), α-Fe, Fe<inf>2</inf>O<inf>3</inf> and Fe<inf>3</inf>O<inf>4</inf>. The magnetic field promoted the thermal decomposition of Sm<inf>2</inf>Fe<inf>17</inf>N<inf>3</inf> in this HT condition.

DOI： 10.1007/s10751-024-01942-w

Koyama K., Mitsui Y., Imatsuji S., Onaka A., Kobayashi R., Onoue M., Onodera R. . Study of heat treatment effect on magnetic properties of MnFeGe using <sup>57</sup>Fe Mössbauer spectroscopy . Interactions245 ( 1 ) 2024年12月査読

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

Mitsui Y., Baba K., Kobayashi R., Onoue M., Ito W., Kuzuhara S., Koyama K. . High magnetic field effects on the phase separation behaviour of Fe-15mass%Cu alloys probed by 57Fe Mössbauer spectroscopy . Interactions245 ( 1 ) 2024年12月

記述言語：日本語出版者・発行元：Interactions

High magnetic field effects on the phase separation of Fe-rich and Cu-rich phases in Fe-15mass%Cu were investigated using microstructural observation and <sup>57</sup>Fe Mössbauer spectroscopy. Fe-15mass%Cu annealing was carried out at 773 K with or without a 5 T magnetic field. Microstructural observations showed that the Fe-rich grains were separated by a Cu-rich phase, and the width of the Cu-rich phase for the samples annealed at 5 T tended to be narrower than that of the samples annealed at 0 T. The Mössbauer spectrum of the samples measured at room temperature is represented by two sub-spectra. The hyperfine fields B<inf>hf</inf> of the two sub-spectra were 33.0–33.1 T and 31.4–31.7 T and they did not change with annealing time or the presence of a magnetic field. The spectrum with a higher (lower) B<inf>hf</inf> corresponded to the centre (near the grain boundary) of the Fe-rich grain. The occupancy of the spectrum with a lower B<inf>hf</inf> for the sample annealed at 5 T was larger than that for the sample annealed at 0 T by up to 5%. This indicated that the change of Cu concentration at the grain boundary became gentle. Therefore, the high magnetic field effects were coarsening of the Fe-rich grains and a gentle change in the Cu concentration at the grain boundary.

DOI： 10.1007/s10751-024-01939-5

Kobayashi R., Mitsui Y., Yoshizaki Y., Takahashi K., Takamine K., Koyama K. . Controlling the growth of yeast by culturing in high magnetic fields . Journal of Magnetism and Magnetic Materials586 2023年11月査読

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

The effect of static magnetic fields up to a strength of 15 T on the growth of three types of yeast which were all classified as Saccharomyces cerevisiae was studied. The growth rate of the yeasts was suppressed by applying a magnetic field. The degree of suppression depended on the type of yeast. The reduction in the numbers of yeast cells was due to growth suppression, not sterilization. Among the three types of Saccharomyces cerevisiae, the degree of suppression on the growth of two yeasts was strongest in a magnetic field at 8 T with different suppression degree of 19% and 12% for a culture time of 24 h. Growth of the other yeast most suppressed by 10% at a magnetic field of around 4 T. Therefore, the yeasts have their characteristic magnetic field sensitivity on the growth. The results were discussed using a model based on the competition between yeast osmotic pressure changes by magnetic field and magnetic forces induced by magnetic field gradient. In low magnetic field regions, change of the osmotic pressure shrink the yeast cell and reduce the contact frequency between yeast cells and glucose-based ions. In higher magnetic field regions, effect of magnetic force become apparent, and recover the growth rate of the yeast. It suggested that the selective growth of yeast can be expected by in-magnetic-field culturing.

DOI： 10.1016/j.jmmm.2023.171193

Takaoka T., Mitsui Y., Koyama K., Fujii S. . Site Selectivity and Structural Stabilization in Cu-Doped or Fe-Doped MnCoGe . MATERIALS TRANSACTIONS64 ( 9 ) 2109 - 2112 2023年9月査読

記述言語：英語出版者・発行元：公益社団法人日本金属学会

We performed first-principles calculations to investigate the effect of Cu or Fe partial substitution in MnCoGe on the stabilization of the hexagonal structure. In the case of Cu partial substitution at x = 0.125, a substitution for one site is more effective than that for both sites. In the case of Fe partial substitution at x = 0.125, there is no difference between two types of substitution for both sites and the Mn site. The result of Fe partial substitution at x = 0.25 indicates that Fe partial substitution for both sites is more effective than that for the Mn or the Co site.

DOI： 10.2320/matertrans.mt-mg2022011

Nakamoto K., Mitsui Y., Kobayashi R., Koyama K. . In-Magnetic-Field Heat Treatment Effects on Phase Growth of Mn–Bi–Sn Composite . MATERIALS TRANSACTIONS64 ( 9 ) 2113 - 2117 2023年9月査読

記述言語：英語出版者・発行元：公益社団法人日本金属学会

To investigate the magnetic field effect on the synthesis reaction and phase growth in a Mn–Bi–Sn composite pellet, in-field heat treatments were performed in 5 T at 573 K for 1 to 48 hours. X-ray diffraction measurements and electron probe micro analysis revealed that MnBi phase did not appear but Mn3Sn, Mn3Sn2 and MnSn2 phases were detected in the pellet. In zero-field heat treatment, the phase fraction of Mn3Sn2 increased and that of MnSn2 decreased as the heat treatment time increased. In contrast, no significant change in the phase fractions of Mn3Sn2 and MnSn2 phase was observed in 5 T even if the heat treatment time was increased to 48 h. The obtained results suggested that the application of magnetic field suppressed the diffusion of Mn atoms between Mn–Sn phases.

DOI： 10.2320/matertrans.mt-mg2022014

Masahira ONOUE, Yoshifuru MITSUI, Saki IMATSUJI, Ryota KOBAYASHI, Reisho ONODERA, Keiichi KOYAMA . Magnetic Properties of MnFeGe Probed Using 57Fe Mössbauer-spectroscopy . JPS Conference Proceedings38 - 011139 2023年5月査読

Yoshifuru MITSUI, Hideto TANAKA, Masahira ONOUE, Moriharu NAGANO, Ryota KOBAYASHI, Rie Y. UMETSU, Keiichi KOYAMA . Magnetic and Hyperfine Properties of FeZnSb . JPS Conference Proceedings38 011138 2023年5月査読

Onaka A., Onoue M., Onodera R., Mitsui Y., Koyama K. . Magnetic and structural properties of Fe-substituted MnCoGe with Ni<inf>2</inf>In-type structure . Journal of Magnetism and Magnetic Materials563 170000 - 170000 2022年12月査読

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

Takahashi J., Mitsui Y., Onoue M., Kobayashi R., Koyama K. . Nitridation kinetics of Sm<inf>2</inf>Fe<inf>17</inf> probed using Mössbauer spectroscopy . Journal of Magnetism and Magnetic Materials554 2022年7月査読

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

Fujii S., Mitsui Y., Koyama K. . Ab initio Study of Atomic-disorder Effect on Electronic and Magnetic Properties of CrAGe . Journal of the Physical Society of Japan91 ( 6 ) 2022年6月査読

記述言語：英語出版者・発行元：Journal of the Physical Society of Japan

First-principles calculations show that the atomic disorder between Al and Ge does not destroy the half-metallic character of CrAlGe, and that its unique character is, however, destroyed by the swap between Cr and Al (or Ge). Our analysis of the X-ray diffraction patterns of CrAlGe indicates the existence of this swap disorder.

DOI： 10.7566/JPSJ.91.064706

Kobayashi R., Mitsui Y., Umetsu R.Y., Takahashi K., Koyama K. . Acceleration of B2/L2<inf>1</inf> order-disorder transformation in Ni<inf>2</inf>MnAl Heusler alloys by in-magnetic-field annealing . Journal of Magnetism and Magnetic Materials547 2022年4月査読

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

Ferromagnetic L21 phase of Ni2MnAl with high order degree is difficult to synthesize because of low L21/B2 order-disorder transformation temperature. It is found that magnetic field accelerated the transformation from the antiferromagnetic disordered B2 to ordered L21 phase. Magnetization increased by in-magnetic-field annealing at 673 K, which indicated the acceleration of the ordering to L21 phase. Magnetic field effects on the B2/L21 order-disorder transformation were discussed based on magnetic-field-induced change of transformation temperature, enhancement of degree of order at annealing temperature, and reduction of critical radius of L21 nuclei. Growth kinetics of L21 phase were evaluated by Johnson-Mehl-Avrami equation, which indicated that 15-T annealing accelerated the growth of L21 phase 5.7 times faster than zero-field annealing. Our results showed that magnetic field can contribute to shortening the annealing time for synthesis of ferromagnetic L21-Ni2MnAl alloy.

DOI： 10.1016/j.jmmm.2021.168908

Mitsui Y., Onoue M., Kobayashi R., Sato K., Kuzuhara S., Ito W., Takahashi K., Koyama K. . High Magnetic Field Effects on Cu-precipitation Behavior of Fe-1mass%Cu at 773 K . ＩＳＩＪ　Ｉｎｔｅｒｎａｔｉｏｎａｌ62 ( 3 ) 413 - 417 2022年3月査読

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

Hiroi M. . High magnetic field properties in Ru2-xFexCrSi with antiferromagnetic and spin-glass states . Physical Review B103 ( 9 ) 2021年3月査読

Kobayashi Ryota, Mitsui Yoshifuru, Umetsu Rie Y., Mizuguchi Masaki, Koyama Keiichi . Synthesis of Ferromagnetic τ-Mn–Al–C by Reactive Sintering . MATERIALS TRANSACTIONS62 ( 1 ) 130 - 134 2021年査読

記述言語：英語出版者・発行元：公益社団法人日本金属学会

<p>Ferromagnetic Mn–Al–C (τ-phase) can be synthesized by a single-route conventional reactive sintering method. The maximum magnetization and coercivity were 75.8 Am<sup>2</sup>/kg and 57 mT, respectively. The τ-phase fraction was evaluated to be 81 mass% for Mn<sub>55</sub>Al<sub>45</sub>C<sub>2</sub> annealed at 1273 K. The τ-phase of Mn<sub>55</sub>Al<sub>45</sub>C<sub>2</sub> can be synthesized at an annealing temperature from 873 to 1273 K, whereas that of Mn<sub>55</sub>Al<sub>45</sub> cannot be synthesized. It was indicated that the phase stability of the hcp-phase (ε-phase) was improved by adding carbon, resulting in an ε–τ transformation.</p>

DOI： 10.2320/matertrans.MT-M2020166

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