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Journal Articles

Ultralow-energy magnon anomaly in yttrium iron garnet

Shamoto, Shinichi; Yasui, Yukio*; Matsuura, Masato*; Akatsu, Mitsuhiro*; Kobayashi, Yoshiaki*; Nemoto, Yuichi*; Ieda, Junichi

Physical Review Research (Internet), 2(3), p.033235_1 - 033235_6, 2020/08

Ultralow energy magnon in yttrium iron garnet crystal has been studied by inelastic neutron scattering in an energy range from 10 to 45 $$mu$$eV. When a magnetic field of about 0.1 T is applied along [111], ultralow energy magnon anomaly is found at 10 K.

Journal Articles

High-temperature short-range order in Mn$$_3$$RhSi

Yamauchi, Hiroki; Sari, D. P.*; Watanabe, Isao*; Yasui, Yukio*; Chang, L.-J.*; Kondo, Keietsu; Ito, Takashi; Ishikado, Motoyuki*; Hagihara, Masato*; Frontzek, M. D.*; et al.

Communications Materials (Internet), 1, p.43_1 - 43_6, 2020/07

High-temperature short-range order is discovered up to 720 K in Mn$$_3$$RhSi by complementary use of neutron scattering and muon spin relaxation measurements.

Journal Articles

Electronic structures of ferromagnetic superconductors UGe$$_{2}$$ and UCoGe studied by angle-resolved photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.

Physical Review B, 91(17), p.174503_1 - 174503_9, 2015/05

 Times Cited Count:21 Percentile:70.36(Materials Science, Multidisciplinary)

The electronic structures of the ferromagnetic superconductors UGe$$_2$$ and UCoGe in the paramagnetic phase were studied by angle-resolved photoelectron spectroscopy using soft X-rays ($$h nu$$ = 400-500 eV). The quasi-particle bands with large contributions from U 5$$f$$ states were observed in the vicinity of EF, suggesting that the U 5$$f$$ electrons of these compounds have an itinerant character. Their overall band structures were explained by the band-structure calculations treating all the U 5$$f$$ electrons as being itinerant. Meanwhile, the states in the vicinity of EF show considerable deviations from the results of band-structure calculations, suggesting that the shapes of Fermi surface of these compounds are qualitatively different from the calculations, possibly caused by electron correlation effect in the complicated band structures of the low-symmetry crystals. Strong hybridization between U 5$$f$$ and $$mathrm{Co} 3d$$ states in UCoGe were found by the $$mathrm{Co}$$ 2p-3d resonant photoemission experiment, suggesting that $$mathrm{Co} 3d$$ states have finite contributions to the magnetic, transport, and superconducting properties.

Journal Articles

Angle resolved photoelectron spectroscopy study of heavy fermion superconductor UPd$$_{2}$$Al$$_{3}$$

Fujimori, Shinichi; kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; et al.

JPS Conference Proceedings (Internet), 3, p.011072_1 - 011072_5, 2014/06

In this presentation, we review some of our recent photoemission studies on uranium superconductors by means of soft X-ray synchrotron radiation ARPES (SX-ARPES). Results of SX-ARPES study on URhGe and UPd$$_{2}$$Al$$_{3}$$ will be presented. URhGe is a ferromagnetic superconductor with $$T_{rm Curie}$$ = 9.5 K and $$T_{rm SC}$$ = 0.26 K while UPd$$_{2}$$Al$$_{3}$$ is an antiferromagnetic superconductor with $$T_{rm N}$$ = 14 K and $$T_{rm SC}$$ = 1.8 K. We have revealed the three-dimensional electronic structures of those compounds by SX-ARPES, and they are compared with those calculated by LDA.

Journal Articles

Weak ferromagnetic ordering disordered by Rh$$^{3+}$$ ions for LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$

Asai, Shinichiro*; Okazaki, Ryuji*; Terasaki, Ichiro*; Yasui, Yukio*; Igawa, Naoki; Kakurai, Kazuhisa

JPS Conference Proceedings (Internet), 3, p.014034_1 - 014034_6, 2014/06

We have carried out the neutron scattering measurements for a single crystal of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$ in order to investigate the ferromagnetic ordering induced by Rh$$^{3+}$$ substitution for Co$$^{3+}$$ of LaCoO$$_{3}$$. The ordered moment is evaluated to be 0.4$$pm$$0.2$$mu$$$$_{B}$$, which is consistent with the saturation magnetization of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$. It indicates that the ferromagnetic ordering of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$ originates from the short-range ferromagnetic ordering disordered by Rh$$^{3+}$$ ions.

Journal Articles

Itinerant magnetism in URhGe revealed by angle-resolved photoelectron spectroscopy

Fujimori, Shinichi; kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi*; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; et al.

Physical Review B, 89(10), p.104518_1 - 104518_7, 2014/03

 Times Cited Count:18 Percentile:64.79(Materials Science, Multidisciplinary)

The electronic structure of the ferromagnetic superconductor URhGe in the paramagnetic phase has been studied by angle-resolved photoelectron spectroscopy using soft X rays ($$hnu$$ = 595-700 eV). Dispersive bands with large contributions from U 5$$f$$ states were observed in the ARPES spectra, and form Fermi surfaces. The band structure in the paramagnetic phase is partly explained by the band-structure calculation treating all U 5$$f$$ electrons as being itinerant, suggesting that an itinerant description of U 5$$f$$ states is a good starting point for this compound. On the other hand, there are qualitative disagreements especially in the band structure near the Fermi level ($$E$$$$_{rm B}$$ $$_sim^{<}$$ 0.5 eV). The experimentally observed bands are less dispersive than the calculation, and the shape of the Fermi surface is different from the calculation. The changes in spectral functions due to the ferromagnetic transition were observed in bands near the Fermi level, suggesting that the ferromagnetism in this compound has an itinerant origin.

Journal Articles

Spin state of Co$$^{3+} $$ in LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ investigated by structural phenomena

Asai, Shinichiro*; Okazaki, Ryuji*; Terasaki, Ichiro*; Yasui, Yukio*; Kobayashi, Wataru*; Nakao, Akiko*; Kobayashi, Kensuke*; Kumai, Reiji*; Nakao, Hironori*; Murakami, Yoichi*; et al.

Journal of the Physical Society of Japan, 82(11), p.114606_1 - 114606_6, 2013/11

 Times Cited Count:6 Percentile:45.93(Physics, Multidisciplinary)

Neutron and synchrotron X-ray diffraction for LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ have been carried out in order to investigate the structural properties related with the spin state of Co$$^{3+}$$ ions. We have found that the values of the Co(Rh)-O bond lengths in the Co(Rh)O$$_{6}$$ octahedron of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$ are nearly identical at 10 K. The lattice volume for the Rh$$^{3+}$$ substituted samples decreases with the thermal expansion coefficient similar to that of LaCoO$$_{3}$$ from room temperature, and ceases to decrease around 70 K. These experimental results favor a mixed state consisting of the high-spin state and low-spin state Co$$^{3+}$$ ions, and suggest that the high-spin state Co$$^{3+}$$ ions are thermally excited in addition to those pinned by the substituted Rh$$^{3+}$$ ions.

Journal Articles

Observation of bulk band dispersions of YbRh$$_2$$Si$$_2$$ using soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira*; Saito, Yuji; Fujimori, Shinichi; kawasaki, Ikuto*; Okane, Tetsuo; Takeda, Yukiharu; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma*; Haga, Yoshinori; et al.

Physical Review B, 87(7), p.075131_1 - 075131_6, 2013/02

 Times Cited Count:6 Percentile:31.87(Materials Science, Multidisciplinary)

We have performed soft X-ray angle-resolved photoemission spectroscopy (ARPES) measurements on YbRh$$_2$$Si$$_2$$ and clarified its three-dimensional bulk valence-band structures. The ARPES spectra have not only Yb$$^{3+}$$ multiplet peaks but also a finite contribution of Yb$$^{2+}$$ peaks at 15 K, corresponding to the valence fluctuating behavior in this compound. This means that Yb 4f electrons in this compound have itinerant character below the $$T_{rm K}$$. We have found that dispersions of the valence bands except the vicinity of the Yb 4f bands agree better with those of the band-structure calculation of LuRh$$_2$$Si$$_2$$ than those of YbRh$$_2$$Si$$_2$$ within a local-density approximation. In addition, the Yb 3d-4f resonant photoemission spectra of YbRh$$_2$$Si$$_2$$ strongly suggest the existence of Yb 5d electrons in the valence band. We conclude that the charge transfer from the Yb 4f state to the Yb 5d state has an important role in the formation of the valence band of YbRh$$_2$$Si$$_2$$.

Journal Articles

Electronic structure of heavy fermion uranium compounds studied by core-level photoelectron spectroscopy

Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 81(1), p.014703_1 - 014703_9, 2012/01

 Times Cited Count:36 Percentile:82.97(Physics, Multidisciplinary)

High-energy-resolution core-level and valence-band photoelectron spectroscopic studies were performed for the heavy Fermion uranium compounds UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, UNi$$_2$$Al$$_3$$, UPd$$_2$$Al$$_3$$, and UPt$$_3$$ as well as typical localized and itinerant uranium compounds to understand the relationship between the uranium valence state and their core-level spectral line shapes. The core-level spectra of UGe$$_2$$, UCoGe, URhGe, URu$$_2$$Si$$_2$$, and UNi$$_2$$Al$$_3$$ are rather similar to those of itinerant compounds, suggesting that U 5$$f$$ electrons in these compounds are well hybridized with ligand states. On the other hand, the core-level spectra of UPd$$_2$$Al$$_3$$ and UPt$$_3$$ show considerably different spectral line shapes from those of the itinerant compounds, suggesting that U 5$$f$$ electrons in UPd$$_2$$Al$$_3$$ and UPt$$_3$$ are less hybridized with ligand states, leading to the correlated nature of U 5$$f$$ electrons in these compounds.

Journal Articles

Characteristic heavy fermion properties in YbCu$$_2$$Si$$_2$$ and YbT$$_2$$Zn$$_{20}$$ (T: Co, Rh, Ir)

Onuki, Yoshichika; Yasui, Shinichi*; Matsushita, Masaki*; Yoshiuchi, Shingo*; Oya, Masahiro*; Hirose, Yusuke*; Dung, N. D.*; Honda, Fuminori*; Takeuchi, Tetsuya*; Settai, Rikio*; et al.

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA003_1 - SA003_6, 2011/12

Journal Articles

Itinerant U 5$$f$$ nature in antiferromagnet U(Ru$$_{0.97}$$Rh$$_{0.03}$$)$$_{2}$$Si$$_{2}$$; Soft X-ray angle-resolved photoemission spectroscopy

Kawasaki, Ikuto; Fujimori, Shinichi; Okane, Tetsuo; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 80(12), p.124710_1 - 124710_5, 2011/12

 Times Cited Count:6 Percentile:45.33(Physics, Multidisciplinary)

We have carried out soft X-ray angle-resolved photoemission spectroscopy experiments on U(Ru$$_{0.97}$$Rh$$_{0.03}$$)$$_{2}$$Si$$_{2}$$, which shows antiferromagnetic (AFM) ordering at low temperatures. We have revealed that U 5$$f$$ electrons contribute to the formation of the energy band as well as Fermi surface. This suggests that the AFM ordering is caused by a spin density wave of itinerant U 5$$f$$ electrons. The observed band dispersion and Fermi surface are nearly identical to those of URu$$_{2}$$Si$$_{2}$$. Therefore, the AFM ordering vector $$Q$$ = (1,0,0) can be a possible ordering vector of the hidden order phase in URu$$_{2}$$Si$$_{2}$$.

Journal Articles

Electronic structure of YbCu$$_2$$Ge$$_2$$ studied by soft X-ray angle-resolved photoemission spectroscopy

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.

Physical Review B, 84(19), p.195121_1 - 195121_6, 2011/11

 Times Cited Count:7 Percentile:34.76(Materials Science, Multidisciplinary)

We have measured three-dimensional band structure and Fermi surfaces (FSs) of YbCu$$_2$$Ge$$_2$$, which has recently become recognized as a nearly divalent Yb-based compound, by using soft X-ray angle-resolved photoemission spectroscopy. We clarified that the bands with finite Yb 4$$f$$ contribution cross the Fermi level and are slightly involved in the formation of the FSs, in line with the valence-fluctuating state of YbCu$$_2$$Ge$$_2$$. The obtained valence-band dispersions and the FSs are well explained by a relativistic band-structure calculation based on a local-density-approximation (LDA). These results suggest that the LDA calculation is a good starting point for understanding of the electronic state of YbCu$$_2$$Ge$$_2$$ as well as nearly divalent Yb-based compounds.

Journal Articles

Resonant angle-resolved photoelectron spectroscopy of substitutional solid solutions of CeRu$$_2$$Si$$_2$$

Okane, Tetsuo; Kawasaki, Ikuto; Yasui, Akira; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; et al.

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA060_1 - SA060_3, 2011/07

 Times Cited Count:1 Percentile:11.83(Physics, Multidisciplinary)

Journal Articles

Relation between metamagnetic transition and quantum critical point in heavy fermion compound YbIr$$_2$$Zn$$_{20}$$

Onuki, Yoshichika; Yasui, Shinichi*; Yoshiuchi, Shingo*; Oya, Masahiro*; Matsushita, Masaki*; Hirose, Yusuke*; Takeuchi, Tetsuya*; Honda, Fuminori*; Settai, Rikio*; Sugiyama, Kiyohiro*; et al.

Journal of Physics; Conference Series, 273, p.012013_1 - 012013_4, 2011/02

 Times Cited Count:0 Percentile:0.03

Journal Articles

Soft X-ray angle-resolved photoemission study of YbCu$$_2$$Ge$$_2$$

Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.

Journal of Physics; Conference Series, 273, p.012067_1 - 012067_4, 2011/02

 Times Cited Count:3 Percentile:65.37

Soft X-ray photoemission spectroscopies have been performed on YbCu$$_2$$Ge$$_2$$, which is thought to be a Yb divalent system, to investigate its bulk electronic structure including Yb 4$$f$$ electrons. Small but finite Yb$$^{3+}$$ multiplet peaks were found at 6$$sim$$12 eV in the angle-integrated spectrum, suggesting that it is a valence fluctuation compound. An "anti-crossing" Yb 4$$f$$ bands with conduction bands were observed in the angle-resolved spectrum. This is the evidence that the Yb 4$$f$$ electrons form a band state through the hybridization with Ge 4$$p$$ and Cu 3$$d$$ electrons.

Journal Articles

Metamagnetic behavior in heavy-fermion compound YbIr$$_2$$Zn$$_{20}$$

Takeuchi, Tetsuya*; Yasui, Shinichi*; Toda, Masatoshi*; Matsushita, Masaki*; Yoshiuchi, Shingo*; Oya, Masahiro*; Katayama, Keisuke*; Hirose, Yusuke*; Yoshitani, Naohisa*; Honda, Fuminori*; et al.

Journal of the Physical Society of Japan, 79(6), p.064609_1 - 064609_15, 2010/06

 Times Cited Count:39 Percentile:83.87(Physics, Multidisciplinary)

Journal Articles

Band structures of CeRu$$_2$$(Si$$_{1-x}$$Ge$$_{x}$$)$$_2$$ studied by resonant soft X-ray ARPES

Okane, Tetsuo; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; Sugi, Motoki*; et al.

Physica Status Solidi (B), 247(3), p.397 - 399, 2010/03

Journal Articles

Heavy fermion state in YbIr$$_2$$Zn$$_{20}$$

Yoshiuchi, Shingo*; Toda, Masatoshi*; Matsushita, Masaki*; Yasui, Shinichi*; Hirose, Yusuke*; Oya, Masahiro*; Katayama, Keisuke*; Honda, Fuminori*; Sugiyama, Kiyohiro*; Hagiwara, Masayuki*; et al.

Journal of the Physical Society of Japan, 78(12), p.123711_1 - 123711_4, 2009/12

 Times Cited Count:37 Percentile:83.11(Physics, Multidisciplinary)

Journal Articles

Observation of itinerant Ce 4$$f$$ electronic states in CeIrSi$$_3$$ studied by angle-resolved Ce 3$$drightarrow 4f$$ resonance photoemission spectroscopy

Okochi, Takuo*; Toshimitsu, Takafumi*; Yamagami, Hiroshi; Fujimori, Shinichi; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Miyauchi, Yuichiro*; et al.

Journal of the Physical Society of Japan, 78(8), p.084802_1 - 084802_6, 2009/08

 Times Cited Count:9 Percentile:53.45(Physics, Multidisciplinary)

We have applied angle-resolved Ce 3$$d{rightarrow}$$4$$f$$ resonance photoemission spectroscopy to the non-centrosymmetric pressure-induced superconductor CeIrSi$$_3$$ and obtained the 4$$f$$ band-structure and Fermi surfaces. We have found that the Ce 4$$f$$ states are located mainly near the Fermi level and that the photoemission intensity derived from the dispersive conduction bands across the Fermi level shows considerable resonant enhancement. In addition, the band structure and Fermi surfaces of CeIrSi$$_3$$ are different from those of the non-$$f$$ reference compound, LaIrSi$$_3$$ and the difference is well explained by the band structure calculated within the local density approximation (LDA). These results strongly suggest that the Ce 4$$f$$ electrons in CeIrSi$$_3$$ are well hybridized with conduction bands and form itinerant electronic states.

Journal Articles

4$$f$$-derived Fermi surfaces of CeRu$$_2$$(Si$$_{1-x}$$Ge$$_{x}$$)$$_2$$ near the quantum critical point; Resonant soft-X-ray ARPES study

Okane, Tetsuo; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; Sugi, Motoki*; et al.

Physical Review Letters, 102(21), p.216401_1 - 216401_4, 2009/05

 Times Cited Count:26 Percentile:76.46(Physics, Multidisciplinary)

46 (Records 1-20 displayed on this page)