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論文

Massive Dirac magnons in the three-dimensional honeycomb magnetic oxide FeTiO

Chung, J.-H.*; Kwangwoo, S.*; Yokoo, Tetsuya R.; 植田大地*; 今井正樹; Kim, H.-S.; Kiem, D. H.; Han, M. J.*; 社本真一

Scientific Reports (Internet), 15, p.5978_1 - 5978_10, 2025/02

https://doi.org/10.1038/s41598-025-90478-2

被引用回数：0 パーセンタイル：0.00(Multidisciplinary Sciences)

Two dimensional honeycomb ferromagnets host massless Dirac magnons which are a bosonic analogue of Dirac fermions in graphene. The Dirac magnons may become massive and topological when the time-reversal symmetry breaks and an energy gap opens up at the Dirac point, which was experimentally observed in Cr $^{3+}$ -based van der Waals magnets. Here, we investigate the spin wave excitations in the magnetic oxide FeTiO with Fe $^{2+}$ electrons (). Using inelastic neutron scattering, we observe two magnon bands separated by a 1.2-meV gap at the Dirac points indicating that its Dirac magnons are massive. Using the linear spin-wave and density functional theory calculations, we find that the spin-orbit-coupled antisymmetric Dzyaloshinskii-Moriya exchanges can best account for the observed Dirac gap opening. The associated Berry curvature and Chern number () indicate that FeTiO hosts topological spin excitations via time-reversal symmetry breaking of Dirac magnons.

論文

Magnetic excitation in the hyperkagome antiferromagnet Mn $_{3}$ RhSi

社本真一; 山内宏樹; 飯田一樹*; 池内和彦*; 金子耕士; Chen, Y.-S.*; 矢野真一郎*; Hsu, P.-T.*; Lee, M. K.*; Hall, A. E.*; et al.

Physical Review Research (Internet), 6(3), p.033303_1 - 033303_7, 2024/09

https://doi.org/10.1103/PhysRevResearch.6.033303

Mn $_{3}$ RhSiの磁気励起は少なくとも0.3から140meVに広がる。200Kでの非弾性散乱強度を積分することで、Mnサイト当たり約5 $mu_{B}$ の磁気モーメントは、約5 $mu_{B}$ であることがわかった。一方で、長距離磁気秩序の磁気モーメントは4Kでわずか2.61 $mu_{B}$ であり、多くの部分が低温まで揺らいでいることがわかった。

論文

Inelastic neutron scattering study of magnon excitation by ultrasound injection in yttrium iron garnet

社本真一; 赤津光洋*; Chang, L.-J.*; 根本祐一*; 家田淳一

Applied Physics Letters, 124(11), p.112402_1 - 112402_5, 2024/03

https://doi.org/10.1063/5.0189768

被引用回数：1 パーセンタイル：35.22(Physics, Applied)

YFeO $_{12}$ における超音波注入によるマグノン励起を非弾性中性子散乱によって研究した。その結果、縦波と横波の両方で超音波注入によりマグノン励起の非弾性中性子散乱強度が増強されることがわかった。

論文

Quantum critical behavior of the hyperkagome magnet MnCoSi

山内宏樹; Sari, D. P.*; 安井幸夫*; 坂倉輝俊*; 木村宏之*; 中尾朗子*; 大原高志; 本田孝志*; 樹神克明; 井川直樹; et al.

Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02

https://doi.org/10.1103/PhysRevResearch.6.013144

-Mn-type family alloys Mn have three-dimensional antiferromagnetic (AFM) corner-shared triangular network. The antiferromagnet MnRhSi shows magnetic short-range order (SRO) over a wide temperature range of approximately 500 K above the Nel temperature $T_{rm N}$ = 190 K. MnCoSi has the smallest lattice parameter and the lowest $T_{rm N}$ in the family compounds. The quantum critical point (QCP) from AFM to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 of MnCoSi is only 140 K, quantum critical behavior is observed in MnCoSi as the enhancement of the electronic specific heat coefficient . We study how the magnetic SRO appears in MnCoSi by using neutron scattering, SR, and physical property measurements. The experimental results show that the neutron scattering intensity of the magnetic SRO does not change much regardless of the suppressed magnetic moment in the long-range magnetic ordered state compared to those of MnRhSi. The initial asymmetry drop ratio of SR above $T_{rm N}$ becomes small, and the magnetic SRO temperature $T_{SRO}$ is suppressed to 240 K. The results suggest that the MnCoSi is close to the QCP in the Mn system.

論文

Spiral spin cluster in the hyperkagome antiferromagnet Mn $_{3}$ RhSi

社本真一; 山内宏樹; 飯田一樹*; 池内和彦*; Hall, A. E.*; Chen, Y.-S.*; Lee, M. K.*; Balakrishnan, G.*; Chang, L.-J.*

Communications Physics (Internet), 6, p.248_1 - 248_6, 2023/09

https://doi.org/10.1038/s42005-023-01363-1

被引用回数：2 パーセンタイル：38.73(Physics, Multidisciplinary)

Mn $_{3}$ RhSi単結晶の中性子散乱測定により、局所スピン相関秩序がらせん構造を持つことがわかった。磁気クラスター形成の起源の可能性を、リフシッツ不変量とグリフィス相の観点から議論し、Co $_{7}$ Zn $_{7}$ Mn $_{6}$ の室温スキルミオン相とMnの非フェルミ液体挙動と比較した。

論文

Magnon mode transition in real space

飯田一樹*; 樹神克明; 稲村泰弘; 中村充孝; Chang, L.-J.*; 社本真一

Scientific Reports (Internet), 12, p.20663_1 - 20663_7, 2022/12

https://doi.org/10.1038/s41598-022-22555-9

被引用回数：2 パーセンタイル：27.99(Multidisciplinary Sciences)

イルメナイトFeTiO $_{3}$ 粉末サンプルのスピン励起を、飛行時間非弾性中性子散乱によって測定し、動的磁気ペア密度関数 $D_{M}(r,E)$ を、動的磁気構造因子 $S_{M}(Q,E)$ からフーリエ変換によって初めて得ることに成功した。

論文

Two-step Mott transition in Ni(S,Se); SR studies and charge-spin percolation model

Sheng, Q.*; 金子竜也*; Yamakawa, Kohtaro*; Guguchia, Z.*; Gong, Z.*; Zhao, G.*; Dai, G.*; Jin, C.*; Guo, S.*; Fu, L.*; et al.

Physical Review Research (Internet), 4(3), p.033172_1 - 033172_14, 2022/09

https://doi.org/10.1103/PhysRevResearch.4.033172

A pyrite system NiS $_{2-x}$ Se exhibits a bandwidth controlled Mott transition via (S,Se) substitutions in a two-step process: the antiferromagnetic insulator (AFI) to antiferromagnetic metal (AFM) transition at 0.45 followed by the AFM to paramagnetic metal (PMM) transition at 1.0. Among a few other Mott systems which exhibit similar two-step transitions, Ni(S,Se) is of particular interest because a large intermediate AFM region in the phase diagram would provide unique opportunities to study the interplay between the spin and charge order. By comparing and combining our muon spin relaxation studies and previous neutron scattering studies, here we propose a picture where the spin order is maintained by the percolation of "nonmetallic" localized and dangling Ni moments surrounded by S, while the charge transition from AFI to AFM is caused by the percolation of the conducting paths generated by the Ni-Se-Ni bonds.

論文

Magnetic Bragg peak enhancement under ultrasound injection

社本真一*; 赤津光洋*; 松浦直人*; 河村聖子; 針井一哉*; 小野正雄*; Chang, L.-J.*; 伊藤孝; 根本祐一*; 家田淳一

Physical Review Research (Internet), 4(1), p.013245_1 - 013245_7, 2022/03

https://doi.org/10.1103/PhysRevResearch.4.013245

イットリウム鉄ガーネットの磁気ブラッグピークに対する超音波注入効果を、準弾性中性子散乱によって研究した。磁気ブラッグピークは、温度の低下とともに大幅に強化さる。エネルギー幅は、超音波注入によって引き起こされる試料温度上昇の平方根に比例して増加した。磁気ブラッグピークは格子振動によって増強されることから、この増強はスピン-格子結合と密接に関連していると予想される。縦波モードで100Kを超えると観測された急激な散乱信号の低下は、スピン-格子結合の劣化を示唆している。これは、温度が100Kを超えるとスピンゼーベック効果が低下することと一致しており、スピン-格子結合による劣化メカニズムに証明を与えている。

論文

Superconducting gap and pseudogap in the surface states of the iron-based superconductor PrFeAsO $_{1-y}$ studied by angle-resolved photoemission spectroscopy

Hagiwara, K.*; 社本真一; 他13名*

Physical Review Research (Internet), 3(4), p.043151_1 - 043151_5, 2021/12

https://doi.org/10.1103/PhysRevResearch.3.043151

In order to study the possible superconductivity at the polar surfaces of 1111-type iron-based superconductors, which is doped with a large amount of holes in spite of the electron doping in bulk materials, we have performed angle-resolved photoemission spectroscopy (ARPES) studies on superconducting PrFeAsO $_{1-y}$ crystals. We have indeed observed the opening of a superconducting gap on surface-derived hole pockets as well as on a bulk-derived hole pocket. The superconducting gap is found to open on the surface-derived hole pockets below the bulk $T_{c}$ , which suggests that the surface superconductivity is possibly induced by proximity effect from the bulk. We have also observed the opening of a large pseudogap on the surface-derived hole pockets, which is similar to the pseudogap in 122-type bulk superconductors doped with a smaller amount of holes. This suggests that the opening of a large pseudogap is a characteristic property of hole-doped iron-based superconductors.

論文

MLFでスピントロニクス研究に挑戦

社本真一; 家田淳一

CROSS T&T, (69), p.35 - 39, 2021/10

https://www.cross.or.jp/tsukuba/reference/cross-tt

J-PARC MLFの高強度中性子によりイットリウム鉄ガーネット結晶で、スピントロニクス関連研究に挑戦した内容について紹介する。

論文

Spin-flop phase in a honeycomb antiferromagnet Mn $_{0.84}$ Mg $_{0.16}$ TiO $_{3}$

社本真一; 山内宏樹; 池内和彦*; Lee, M. K.*; Chang, L.-J.*; Garlea, V. O.*; Hwang, I. Y.*; Lee, K. H.*; Chung, J.-H.*

Journal of the Physical Society of Japan, 90(9), p.093703_1 - 093703_4, 2021/09

https://doi.org/10.7566/JPSJ.90.093703

被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

ハニカム格子反強磁性体Mn $_{0.84}$ Mg $_{0.16}$ TiO $_{3}$ の5T磁場下でのスピンフロップ相の磁気構造を弾性散乱と非弾性散乱を相補的に用いることで、初めて提案した。

論文

Neutron scattering study on yttrium iron garnet for spintronics

南部雄亮*; 社本真一

Journal of the Physical Society of Japan, 90(8), p.081002_1 - 081002_15, 2021/08

https://doi.org/10.7566/JPSJ.90.081002

被引用回数：3 パーセンタイル：30.49(Physics, Multidisciplinary)

スピントロニクス用イットリウム鉄ガーネットの中性子散乱研究について、長期課題2017L0300の"Cross correlation dynamics under a strain field"の成果を中心にSPECIAL TOPICSのReviewとしてまとめた。

論文

Magnetic structure of short-range ordering in intermetallic antiferromagnet MnRhSi

樹神克明; 本田孝志*; 山内宏樹; 社本真一*; 池田一貴*; 大友季哉*

Journal of the Physical Society of Japan, 90(7), p.074710_1 - 074710_7, 2021/07

https://doi.org/10.7566/JPSJ.90.074710

被引用回数：2 パーセンタイル：21.70(Physics, Multidisciplinary)

Magnetic pair distribution function (mPDF) of intermetallic antiferromagnet MnRhSi is estimated from the powder neutron diffraction data. The mPDF exhibits negative peak at about = 2.7 corresponding to the nearest neighbor Mn-Mn distance above the antiferromagnetic transition temperature $T_{N}$ . Below $T_{N}$ , the mPDF is a superposition of the mPDF with the negative peak at about = 2.7 and the mPDF calculated from the antiferromagnetic structure which is determined by the previous neutron diffraction study, indicating the coexistence of the short range ordering and the antiferromagnetic long range ordering. The mPDF of the short range ordering is not reproduced by the magnetic structure model with the symmetry consistent with that of the crystal structure. The possible magnetic structure which can reproduce the observed mPDF of the short range ordering is proposed.

論文

Gallium-effect in a lead-free solder for silver-sheathed superconducting tape

社本真一; Lee, M. K.*; 藤村由希; 近藤啓悦; 伊藤孝; 池内和彦*; 保田諭; Chang, L.-J.*

Materials Research Express (Internet), 8(7), p.076303_1 - 076303_6, 2021/07

https://doi.org/10.1088/2053-1591/ac10d2

被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)

Pb, Ga、およびGaをドープした鉛フリーのSn-Ag-Cuはんだを使用して、銀被覆DI-BISCCOタイプHテープを使用した低接合抵抗率に対するガリウム効果を研究した。その結果について報告する。

論文

Spin wave excitations in honeycomb antiferromagnet MnTiO $_{3}$

Hwang, I. Y.*; Lee, K. H.*; Chung, J.-H.*; 池内和彦*; Garlea, V. O.*; 山内宏樹; 赤津光洋*; 社本真一

Journal of the Physical Society of Japan, 90(6), p.064708_1 - 064708_6, 2021/06

https://doi.org/10.7566/JPSJ.90.064708

被引用回数：5 パーセンタイル：44.31(Physics, Multidisciplinary)

ハニカム格子反強磁性体MnTiO $_{3}$ のスピン波を調べ、スピン間の交換相互作用を正確に求めた。

論文

Magnetic pair distribution function of spin-glass system Mn $_{0.5}$ Fe $_{0.5}$ TiO

樹神克明; 本田孝志*; 池田一貴*; 社本真一; 大友季哉*

JPS Conference Proceedings (Internet), 33, p.011059_1 - 011059_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011059

We have performed powder diffraction measurement on the typical spin-glass system Mn $_{0.5}$ Fe $_{0.5}$ TiO using the neutron total scattering spectrometer NOVA installed in J-PARC to apply the mPDF analysis to the short-range correlation in the spin-glass phase. The mPDF obtained from the magnetic scattering intensity can be reproduced by the linear combination of the mPDFs calculated from the antiferromagnetic structures of MnTiO and FeTiO, consistent with the coexistence of two different antiferromagnetic correlations in the spin-glass phase.

論文

Broken C $_{4}$ symmetry in the tetragonal state of uniaxial strained BaCo $_{0.9}$ Ni $_{0.1}$ S $_{1.9}$

社本真一; 山内宏樹; 池内和彦*; 梶本亮一; 家田淳一

Physical Review Research (Internet), 3(1), p.013169_1 - 013169_9, 2021/02

https://doi.org/10.1103/PhysRevResearch.3.013169

A compound with large anions is known to show large compressibility whereby a novel response may emerge from the degenerated state by a uniaxial pressure. Neutron scattering study of BaCo $_{0.9}$ Ni $_{0.1}$ S $_{1.9}$ crystal reveals that the tetragonal insulating state has two magnetic domains with in-plane anisotropic antiferromagnetic wave vectors =(, 0) and =(0, ). One magnetic domain with becomes dominant under a weak uniaxial pressure of 1 MPa without a structural phase transition. Correspondingly, the in-plane broken C $_{4}$ symmetry is observed in the in-plane magnetic excitation. The domain-ratio changes under a uniaxial pressure in the tetragonal state is only slightly smaller than that in the orthorhombic state.