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Journal Articles

Electronic structure of UTe$$_2$$ studied by photoelectron spectroscopy

Fujimori, Shinichi; Kawasaki, Ikuto; Takeda, Yukiharu; Yamagami, Hiroshi; Nakamura, Ai*; Homma, Yoshiya*; Aoki, Dai*

Journal of the Physical Society of Japan, 88(10), p.103701_1 - 103701_5, 2019/10

Journal Articles

$$^{125}$$Te-NMR study on a single crystal of heavy fermion superconductor UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07

We report $$^{125}$$Te-NMR studies on a newly discovered heavy fermion superconductor UTe$$_2$$. Using a single crystal, we have measured the $$^{125}$$Te-NMR Knight shift $$K$$ and spin-lattice relaxation rate $$1/T_1$$ for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static ($$K$$) and dynamical susceptibilities ($$1/T_1$$) in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate $$1/T_2$$, when the field is applied along the easy axis of magnetization (=$$a$$ axis). This behavior suggests the development of longitudinal magnetic fluctuations along the $$a$$ axis at very low frequencies below 20 K.

Journal Articles

Magnetic and electrical properties of the ternary compound U$$_2$$Ir$$_3$$Si$$_5$$ with one-dimensional uranium zigzag chains

Li, D. X.*; Honda, Fuminori*; Miyake, Atsushi*; Homma, Yoshiya*; Haga, Yoshinori; Nakamura, Ai*; Shimizu, Yusei*; Maurya, A.*; Sato, Yoshiki*; Tokunaga, Masashi*; et al.

Physical Review B, 99(5), p.054408_1 - 054408_9, 2019/02

Journal Articles

Effects of magnetic field and pressure on the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$

Takeuchi, Tetsuya*; Yara, Tomoyuki*; Ashitomi, Yosuke*; Iha, Wataru*; Kakihana, Masashi*; Nakashima, Miho*; Amako, Yasushi*; Honda, Fuminori*; Homma, Yoshiya*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 87(7), p.074709_1 - 074709_14, 2018/07

 Times Cited Count:2 Percentile:29.91(Physics, Multidisciplinary)

Journal Articles

Easy-plane XY spin fluctuations in the cycloidal magnet UPtGe studied via field orientation-dependent $$^{195}$$Pt NMR

Tokunaga, Yo; Nakamura, Ai*; Aoki, Dai*; Shimizu, Yusei*; Homma, Yoshiya*; Honda, Fuminori*; Sakai, Hironori; Hattori, Taisuke; Kambe, Shinsaku

Physical Review B, 98(1), p.014425_1 - 014425_5, 2018/07

 Times Cited Count:1 Percentile:59.26(Materials Science, Multidisciplinary)

$$^{195}$$Pt NMR measurements have been performed on a single crystal of the uranium-based compound UPtGe, which is the only 5f system known to possess an incommensurate helical (cycloidal) structure below TN = 50 K. Knight shift measurement confirmed the isotropic character of the static spin susceptibilities in hexagonal-like ac crystal planes of the EuAuGe-type crystal structure. The hyperfine coupling constants were also found to be isotropic in the planes. Nuclear relaxation rate measurement revealed the development of the antiferro-magnetic spin fluctuations with XY character confined to the hexagonal-like plane below 200 K. The results present a clear contrast to the Ising anisotropy of the fluctuations in ferromagnetic superconductors UCoGe and URhGe.

Journal Articles

Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe$$_2$$; $$^{73}$$Ge-NQR study at ambient pressure

Noma, Yuichiro*; Kotegawa, Hisashi*; Kubo, Tetsuro*; To, Hideki*; Harima, Hisatomo*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*; Ito, Kohei*; Haller, E. E.*; et al.

Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03

 Times Cited Count:1 Percentile:49.95(Physics, Multidisciplinary)

Journal Articles

Effect of pressure on magnetism of UIrGe

Pospisil, J.; Gochi, Jun*; Haga, Yoshinori; Honda, Fuminori*; Uwatoko, Yoshiya*; Tateiwa, Naoyuki; Kambe, Shinsaku; Nagasaki, Shoko*; Homma, Yoshiya*; Yamamoto, Etsuji

Journal of the Physical Society of Japan, 86(4), p.044709_1 - 044709_6, 2017/04

 Times Cited Count:5 Percentile:26.6(Physics, Multidisciplinary)

Journal Articles

Switching of magnetic ground states across the UIr$$_{1-x}$$Rh$$_x$$Ge alloy system

Pospisil, J.; Haga, Yoshinori; Kambe, Shinsaku; Tokunaga, Yo; Tateiwa, Naoyuki; Aoki, Dai*; Honda, Fuminori*; Nakamura, Ai*; Homma, Yoshiya*; Yamamoto, Etsuji; et al.

Physical Review B, 95(15), p.155138_1 - 155138_15, 2017/04

 Times Cited Count:6 Percentile:30.1(Materials Science, Multidisciplinary)

Journal Articles

Large reversible magnetocaloric effect in ferromagnetic semiconductor EuS

Li, D. X.*; Yamamura, Tomoo*; Nimori, Shigeki*; Homma, Yoshiya*; Honda, Fuminori*; Haga, Yoshinori; Aoki, Dai*

Solid State Communications, 193, p.6 - 10, 2014/09

 Times Cited Count:10 Percentile:42.74(Physics, Condensed Matter)

Journal Articles

Self-radiation effects and glassy nature of magnetic transition in AmO$$_2$$ revealed by $$^{17}$$O-NMR

Tokunaga, Yo; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori*; Sakai, Hironori; Kambe, Shinsaku; Homma, Yoshiya*; Honda, Fuminori*; Aoki, Dai*; Walstedt, R. E.*

Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06

 Times Cited Count:6 Percentile:58.6(Materials Science, Multidisciplinary)

The magnetic phase transition near $$T_0=8.5$$ K in AmO$$_2$$ has been investigated microscopically by means of $$^{17}$$O NMR. To avoid complexities arising from sample aging associated with the alpha decay of $$^{243}$$Am, all measurements have been performed within 40 days after sample synthesis. Even during such a short period, however, a rapid change of NMR line shape has been observed at 1.5 K, suggesting that the ground state of AmO$$_2$$ is very sensitive to disorder. We have also confirmed the loss of $$^{17}$$O NMR signal intensity over a wide temperature range below $$T_0$$, and more than half of oxygen nuclei are undetectable at 1.5 K. This behavior reveals the persistence of slow and distributed spin fluctuations down to temperatures well below $$T_0$$. In the paramagnetic state, strong NMR line broadening and spatially inhomogeneous spin fluctuations have been observed. The results are all indicative of short-range, spin-glass-like character for the magnetic transition in this system.

Journal Articles

Competition between magnetic ordering and random spin freezing in Dy$$_2$$PtS$$_3$$

Li, D.*; Yamamura, Tomoo*; Homma, Yoshiya*; Yubuta, Kunio*; Shikama, Tatsuo*; Aoki, Dai*; Nimori, Shigeki*; Haga, Yoshinori

Journal of the Korean Physical Society, 62(12), p.2233 - 2238, 2013/06

 Times Cited Count:2 Percentile:73.65(Physics, Multidisciplinary)

Journal Articles

Anisotropic spin fluctuations in the heavy fermion systems; Case studies of CePd$$_5$$Al$$_2$$ and NpPd$$_5$$Al$$_2$$

Sakai, Hironori; Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Haga, Yoshinori; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*; Homma, Yoshiya*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB003_1 - SB003_6, 2012/12

 Times Cited Count:3 Percentile:66.83(Physics, Multidisciplinary)

In the so-called 115 family members with chemical formulae of Ce$$T$$In$$_5$$ ($$T$$=Co, Rh, Ir) and $$An$$$$T$$Ga$$_5$$ ($$An$$=U, Np, Pu), our analysis of the Knight shift and spin-lattice relaxation rates suggests that larger XY-type anisotropy in the antiferromagnetic spin fluctuations in the normal states would favor $$d$$-wave superconductivity with higher $$T_c$$. In order to examine this working hypothesis, the anisotropy ratios of antiferromagnetic fluctuations are derived from our NMR results for the superconductor NpPd$$_5$$Al$$_2$$ and antiferromagnet CePd$$_5$$Al$$_2$$, which are tetragonal compounds with a 115-related structure. CePd$$_5$$Al$$_2$$ shows Ising-type anisotropy, which is the same anisotropy as in the ordered state. On the other hand, NpPd$$_5$$Al$$_2$$ shows XY-type anisotropy just above $$T_c$$.

Journal Articles

Single crystal growth and magnetic anisotropy of hexagonal PuGa$$_{3}$$

Haga, Yoshinori; Homma, Yoshiya*; Aoki, Dai*; Nakajima, Kunihisa; Arai, Yasuo; Matsuda, Tatsuma; Ikeda, Shugo*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB007_1 - SB007_4, 2012/12

 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Uniaxial-pressure control of magnetic phase transitions in a frustrated magnet CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ (x =0, 0.018)

Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.

Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09

Journal Articles

Uniaxial-pressure control of magnetic phase transitions in a frustrated magnet CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ ($$x$$ = 0, 0.018)

Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.

Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09

 Times Cited Count:9 Percentile:39.11(Physics, Multidisciplinary)

Journal Articles

Solid-state NMR study of actinide dioxides

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Chudo, Hiroyuki; Osaka, Masahiko; Miwa, Shuhei; Nishi, Tsuyoshi; Nakada, Masami; Ito, Akinori; Homma, Yoshiya*

Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00

 Percentile:100

Besides the importance of AnO$$_2$$ series (An; U, Np, Pu, Am) as a nuclear fuel, the magnetic properties of these compounds at low temperatures are particularly interesting. Their surprisingly varied physical properties continue to be of interest for both theory and experiment. In this study, we have performed NMR studies for the series of actinide dioxides. On the basis of $$^{17}$$O-NMR studies, exotic magnetic orderings associated with multipole degrees of freedom on 5$$f$$ electrons have been identified in UO$$_2$$ (dipolar + quadrupolar ordering) and NpO$$_2$$ (octupolar + quadrupolar ordering), in contrast with the non-magnetic ground state of PuO$$_2$$. In AmO$$_2$$, our $$^{17}$$O-NMR data provide the first microscopic evidence for a phase transition as a bulk property in this system.

Journal Articles

Actinide-handling experience for training and education of future expert under J-ACTINET

Osaka, Masahiko; Konashi, Kenji*; Hayashi, Hirokazu; Li, D.*; Homma, Yoshiya*; Yamamura, Tomoo*; Sato, Isamu; Miwa, Shuhei; Sekimoto, Shun*; Kubota, Takumi*; et al.

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12

Summer schools for future experts have successfully been completed under Japan Actinide Network (J-ACTINET) for the purpose of development of human resources who are expected to be engaged in every areas of actinide-research/engineering. The first summer school was held in Ibaraki-area in August 2009, followed by the second one in Kansai-area in August 2010. Two summer schools have focused on actual experiences of actinides in actinide-research fields for university students and young researchers/engineers as an introductory course of actinide-researches. Several quasi actinide-handling experiences at the actinide-research fields have attracted attentions of participants at the first school in Ibaraki-area. The actual experiments using actinides-containing solutions have been carried out at the second school in Kansai-area. Future summer schools will be held every year for the sustainable human resource development in various actinide-research fields.

Journal Articles

$$^{237}$$Np nuclear relaxation rate in heavy fermion superconductor NpPd$$_5$$ Al$$_2$$

Chudo, Hiroyuki; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori; Haga, Yoshinori; Matsuda, Tatsuma; Onuki, Yoshichika; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; et al.

Physical Review B, 84(9), p.094402_1 - 094402_5, 2011/09

 Times Cited Count:5 Percentile:68.26(Materials Science, Multidisciplinary)

Journal Articles

NMR study on AmO$$_{2}$$; Comparison with UO$$_{2}$$ and NpO$$_{2}$$

Tokunaga, Yo; Nishi, Tsuyoshi; Kambe, Shinsaku; Nakada, Masami; Homma, Yoshiya*; Sakai, Hironori; Chudo, Hiroyuki

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA110_1 - SA110_3, 2011/07

 Times Cited Count:2 Percentile:75.59(Physics, Multidisciplinary)

We have successfully performed an $$^{17}$$O NMR for the first time on Americium dioxide (AmO$$_2$$). We observed a drastic broadening of the NMR spectrum, after a sudden drop of NMR signal intensity below $$T_0$$. These data provide the first microscopic evidence for a phase transition as a bulk property in this system. In the ordered state, we found a spectrum with a triangular line shape, which resembles neither that of UO$$_2$$ nor NpO$$_2$$. It is also suggested that there is considerable damage to the sample induced by self-radiation effects from the alpha decay of $$^{243}$$Am.

Journal Articles

Crystal structure and physical properties of trigonal NpGa$$_3$$ and Np$$_{3}$$Ga$$_{11}$$

Haga, Yoshinori; Aoki, Dai*; Homma, Yoshiya*; Matsuda, Tatsuma; Ikeda, Shugo*; Sakai, Hironori; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA109_1 - SA109_3, 2011/07

 Percentile:100(Physics, Multidisciplinary)

163 (Records 1-20 displayed on this page)