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Journal Articles

NMR investigation of quadrupole order parameter in actinide dioxides

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Sakai, Hironori; Chudo, Hiroyuki; Ikushima, Kenji*; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu*; et al.

Journal of Optoelectronics and Advanced Materials, 10(7), p.1663 - 1665, 2008/07

Multipolar degrees of freedom characteristic of $$f$$-electrons bring rich and complex physics to rare-earth and actinide compounds. In the present work, we demonstrate that microscopic investigation of multipole order parameters is also possible by means of NMR through the hyperfine interactions. Our $$^{17}$$O NMR study performed on a single crystal of NpO$$_2$$ provide definitive support for the proposed longitudinal triple-$$q$$ type antiferro-octupolar ordering below $$T_0=$$26 K. We shall also provide our $$^{17}$$O NMR results on UO$$_2$$ and PuO$$_2$$. The microscopic NMR clearly indicates the different nature of the magnetic ground states among three actinide dioxides.

Journal Articles

NMR studies of actinide dioxides

Tokunaga, Yo; Sakai, Hironori; Fujimoto, Tatsuya; Kambe, Shinsaku; Walstedt, R. E.*; Ikushima, Kenji*; Yasuoka, Hiroshi; Aoki, Dai*; Homma, Yoshiya*; Haga, Yoshinori; et al.

Journal of Alloys and Compounds, 444-445, p.241 - 245, 2007/10

 Times Cited Count:14 Percentile:64.49(Chemistry, Physical)

In this paper, we present our recent NMR works on Neptunium and Plutonium compounds. In order to elucidate the nature of the exotic multipolar ordered phase of NpO$$_2$$, we have initiated the first NMR measurements on this system. We have shown that direct observation of multipole order parameters is possible by means of NMR. Our NMR results provide further insight into the microscopic nature of multipole phase transitions in f-electron systems. We have also performed $$^{69,71}$$Ga NMR/NQR studies on a single crystal of PuRhGa$$_5$$. From the temperature dependence of the spin-lattice relaxation rate ($$1/T_1$$), we have found that PuRhGa$$_5$$ is an unconventional superconductor having an anisotropic superconducting (SC) gap 2$$Delta(0)$$=5$$K_BT_c$$. Furthermore, we have confirmed the Knight shift to be decreased below $$T_c$$. This gives strong evidence for spin singlet SC pairing.

Journal Articles

Multipolar phase transition in NpO$$_{2}$$; Comparison with UO$$_2$$ from $$^{17}$$O-NMR

Tokunaga, Yo; Homma, Yoshiya*; Kambe, Shinsaku; Aoki, Dai*; Ikushima, Kenji; Sakai, Hironori; Ikeda, Shugo; Yamamoto, Etsuji; Nakamura, Akio; Shiokawa, Yoshinobu; et al.

Journal of the Physical Society of Japan, 75(Suppl.), p.33 - 35, 2006/08

The low-temperature phase transition in NpO$$_2$$ has attracted much attention as a promising candidate for a new class of phase transitions associated with octupolar degrees of freedom. In order to elucidate the nature of this exotic phase transition in NpO$$_2$$, we have initiated the first $$^{17}$$O-NMR measurements on this system using a powder sample. From the $$^{17}$$O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below $$T_0$$= 26 K. It has also been shown that the temperature and field dependence of the $$^{17}$$O NMR spectrum can be understood by considering an unconventional hyperfine interaction between the $$^{17}$$O nuclear spins and field-induced antiferromagnetic moments arising from the longitudinal triple-$$vec{q}$$ antiferro-quadrupolar order. These NMR results give strong evidence for the occurrence of the longitudinal triple-$$vec{q}$$ multipole structure in NpO$$_2$$. We will also discuss our recent $$^{17}$$O-NMR results in a single crystal.

Journal Articles

Direct observation of $$^{235}$$U NMR in an itinerant 5${it f}$ electron system, USb$$_{2}$$

Kato, Harukazu*; Sakai, Hironori; Ikushima, Kenji*; Kambe, Shinsaku; Tokunaga, Yo; Aoki, Dai*; Haga, Yoshinori; Onuki, Yoshichika; Yasuoka, Hiroshi; Walstedt, R. E.

Journal of the Physical Society of Japan, 73(8), p.2085 - 2088, 2004/08

 Times Cited Count:11 Percentile:56.87(Physics, Multidisciplinary)

Diret AFNMR studies of $$^{235}$$U, $$^{121}$$Sb and $$^{123}$$Sb nuclear spins have been carried out in the antiferromagnetic state of USb$$_{2}$$. The central $$^{235}$$U transition have been found as 217.2MHz based on several tests. The $$^{235}$$U hyperfine coupling constant is estimated as 147T/mB. This is the first observation of $$^{235}$$U NMR in a metallic compound.

Journal Articles

Ga NMR/NQR study in UGa$$_{3}$$

Ikushima, Kenji; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika

Journal of Magnetism and Magnetic Materials, 226-230(Part.1), p.89 - 91, 2001/05

no abstracts in English

Journal Articles

Unusual phase transition of UGa$$_{3}$$ observed by Ga NQR

Ikushima, Kenji; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Kambe, Shinsaku; Walstedt, R. E.

Journal of the Physical Society of Japan, Vol.70, Supplement A, p.31 - 33, 2001/05

no abstracts in English

Journal Articles

First-order phase transition in UO$$_{2}$$; $$^{235}$$U and $$^{17}$$O NMR study

Ikushima, Kenji; Tsutsui, Satoshi; Haga, Yoshinori; Yasuoka, Hiroshi; Walstedt, R. E.; Masaki, Nobuyuki; Nakamura, Akio; Nasu, Saburo*; Onuki, Yoshichika

Physical Review B, 63(10), p.104404_1 - 104404_11, 2001/03

 Times Cited Count:73 Percentile:93.37(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

$$^{171}$$Yb NMR in the Kondo semiconductor YbB$$_{12}$$

Ikushima, Kenji; Kato, Y.*; Takigawa, Masashi*; Iga, Fumitoshi*; Hiura, Sayaka*; Takabatake, Toshiro*

Physica B; Condensed Matter, 281-282, p.274 - 275, 2000/06

 Times Cited Count:20 Percentile:70.16(Physics, Condensed Matter)

no abstracts in English

Journal Articles

$$^{235}$$U NMR study of antiferromagnet UO$$_{2}$$

Ikushima, Kenji; Yasuoka, Hiroshi; Tsutsui, Satoshi; Nasu, Saburo*; Masaki, Nobuyuki; Nakamura, Akio; Ueda, Yutaka*

Physica B; Condensed Matter, 281-282, p.197 - 199, 2000/06

 Times Cited Count:2 Percentile:16.19(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Scaling behavior in the Ce-based Kondo semiconductors; NQR/NMR measurements of CeRhSb and CeNiSn under high pressures

Ikushima, Kenji; Yasuoka, Hiroshi; Uwatoko, Yoshiya*; Ishikawa, Yoshikazu*

Physical Review B, 60(21), p.14537 - 14540, 1999/00

 Times Cited Count:5 Percentile:34.48(Materials Science, Multidisciplinary)

no abstracts in English

10 (Records 1-10 displayed on this page)
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