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Journal Articles

Splash plasma channels produced by picosecond laser pulses in argon gas for laser wakefield acceleration

Mizuta, Yoshio*; Hosokai, Tomonao*; Masuda, Shinichi*; Zhidkov, A.*; Makito, Keigo*; Nakanii, Nobuhiko*; Kajino, Shohei*; Nishida, Akinori*; Kando, Masaki; Mori, Michiaki; et al.

Physical Review Special Topics; Accelerators and Beams, 15(12), p.121301_1 - 121301_10, 2012/12

 Times Cited Count:18 Percentile:71.87(Physics, Nuclear)

Journal Articles

$$mu^+$$ diffusion in cubic $$f$$-electron compounds observed by high transverse field $$mu^+$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Heffner, R. H.; Aoki, Yuji*; Suzuki, Hiroyuki*; Onimaru, Takahiro*; Tanida, Hiroshi*; Takagi, Shigeru*

Journal of Physics; Conference Series, 225, p.012021_1 - 012021_6, 2010/06

 Times Cited Count:1 Percentile:53.11

The diffusion of positive muon $$mu^+$$ in condensed matter has been investigated for many years by using $$mu^+$$ spin rotation/relaxation ($$mu^+$$SR) technique. The $$mu^+$$SR studies have provided deep insight into quantum diffusion at low temperatures as well as hopping process at high temperatures, which are closely related to hydrogen dynamics in the dilute limit. We here report transverse field (TF) $$mu^+$$SR studies of the $$mu^+$$ diffusion in cubic $$f$$-electron compounds PrPb$$_3$$ and SmAg$$_2$$In. The $$mu^+$$ site splits into two magnetically labeled sites when high TF is applied to single-crystalline specimens along the [001] direction. The $$mu^+$$SR lines show drastic variation according to the $$mu^+$$ motion between the magnetically labeled sites. From detailed analysis of the $$mu^+$$SR lines, we deduced $$mu^+$$ hopping parameters for both compounds.

Journal Articles

Possible low-energy excitations of multipoles in SmRu$$_4$$P$$_{12}$$ probed by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

Physica B; Condensed Matter, 404(5-7), p.761 - 764, 2009/04

 Times Cited Count:1 Percentile:6.65(Physics, Condensed Matter)

We report on detailed longitudinal field (LF) $$mu$$SR studies in SmRu$$_4$$P$$_{12}$$ in order to characterize magnetic fluctuations in a magnetically ordered state below $$T_{rm MI}=16.5$$ K. A magnitude and fluctuation rate of the fluctuating field are derived as functions of temperature from LF dependence of the longitudinal relaxation rate. Possible low-energy excitations of magnetic multipoles are discussed.

Journal Articles

Novel features in filled skutterudites containing rare-earth elements with a plural number of 4f-electrons

Sato, Hideyuki*; Aoki, Yuji*; Kikuchi, Daisuke*; Sugawara, Hitoshi*; Higemoto, Wataru; Oishi, Kazuki; Ito, Takashi; Heffner, R. H.; Saha, S. R.*; Koda, Akihiro*; et al.

Physica B; Condensed Matter, 404(5-7), p.749 - 753, 2009/04

 Times Cited Count:4 Percentile:22.79(Physics, Condensed Matter)

Wide varieties of strongly correlated electron phenomena are performed on the stage of a filled skutterudite structure. Especially when one of the players contains a plural number of 4f electrons, the orbital degrees of freedom play a major role as a new type of nonmagnetic and/or weak-magnetic phenomena. Several examples found in Pr- and Sm-based filled skutterudites are introduced in relation to muon spin relaxation experiments.

Journal Articles

Quantized hyperfine field at an implanted $$mu^+$$ site in PrPb$$_3$$; Interplay between localized $$f$$ electrons and an interstitial charged particle

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Heffner, R. H.; Aoki, Yuji*; Amato, A.*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

Physical Review Letters, 102(9), p.096403_1 - 096403_4, 2009/03

 Times Cited Count:12 Percentile:61.24(Physics, Multidisciplinary)

Journal Articles

Magnetic properties of SmRu$$_{4}$$P$$_{12}$$ probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

Journal of Physics and Chemistry of Solids, 68(11), p.2072 - 2075, 2007/11

 Times Cited Count:1 Percentile:7.92(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Evolution of local magnetic state in SmRu$$_4$$P$$_{12}$$ probed by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

Journal of the Physical Society of Japan, 76(5), p.053707_1 - 053707_4, 2007/05

 Times Cited Count:27 Percentile:76.48(Physics, Multidisciplinary)

A filled skutterudite compound SmRu$$_4$$P$$_{12}$$ shows metal-insulatortransition at $$T_{rm MI}$$=16.5K with magnetic anomaly. A possibility of magnetic octupole ordering has been discussed on the basis of multipole degrees of freedom belonging to thecrystalline-electric-field ground state. We investigated local magnetic states in the ordered state by using the muon spin relaxation method. An increase of muon spin relaxation rate was detected in zeroapplied field just below $$T_{rm MI}$$, indicating time-reversal-symmetry breaking in the ordered state. This result suggests that the order parameter includes magnetic octupole and/ordipole. Magnitude of the internal field at the muon site monotonically increases with decreasing temperature, growing steeply below $$T^{prime}$$=3K. The longitudinal relaxation rate has a maximum at around $$T^{prime}$$, suggesting suppression of magnetic fluctuations. We discussed these experimental facts on the basis of the multipoledegrees of freedom.

Journal Articles

Muon knight shift measurements on PrPb$$_3$$ in paraquadrupolar state

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Heffner, R. H.; Nishida, Nobuhiko*; Aoki, Yuji*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.743 - 745, 2007/03

PrPb$$_3$$ exhibits antiferroquadrupole ordering at T$$_Q$$ = 0.4 K. In the ordering phase, incommensurate structure of quadruple was found from recent experimental study and much attention is paid to this compound. We performed muon spin rotation and relaxation measurements on a single crystalline sample of PrPb$$_3$$. A quite anisotropic contact-coupling constant was extracted from the muon Knight shift, possibly concerned with nonspherical distribution of 4$$f$$-electron at low temperature. The contact and dipole coupling constants are of comparable magnitudes, suggesting significance of strong hybridization between the $$4f$$ electrons of Pr and the conduction electrons for incommensurate structure.

Journal Articles

Investigation of bulk superconductivity in PrPt$$_5$$

Ito, Takashi; Nishida, Nobuhiko*; Oishi, Kazuki; Higemoto, Wataru; Karaki, Yoshitomo*; Ishimoto, Hidehiko*

Journal of the Physical Society of Japan, 75(Suppl.), p.189 - 191, 2006/08

no abstracts in English

Oral presentation

$$mu$$SR study on multipolar ordering in PrPb$$_3$$, 2

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Heffner, R. H.; Nishida, Nobuhiko*; Aoki, Yuji*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

no journal, , 

no abstracts in English

Oral presentation

Magnetism of SmRu$$_4$$P$$_{12}$$ at low temperature and low field probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

no journal, , 

no abstracts in English

Oral presentation

Anomalous magnetic state in SmRu$$_4$$P$$_{12}$$ detected by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

no journal, , 

no abstracts in English

Oral presentation

Study of static and dynamic properties of multipoles in $$f$$ electron systems

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

no journal, , 

no abstracts in English

Oral presentation

Magnetism of SmRu$$_4$$P$$_{12}$$ at low temperature and low field probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

no journal, , 

no abstracts in English

Oral presentation

Hyperfine-enhanced nuclear magnetism in $$^{141}$$Pr-based compounds observed by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Nishida, Nobuhiko*; Karaki, Yoshitomo*; Ishimoto, Hidehiko*

no journal, , 

Several novel phenomena about higher order multipoles have recently been found in $$^{141}$$Pr-based compounds with a nonmagnetic crystalline-electric-field (CEF) ground state. Previous $$mu$$SR studies in such compounds reported an anomalous muon spin relaxation at low temperatures in spite of the CEF ground state with the nonmagnetic nature, and a hyperfine-enhanced nuclear magnetism was discussed as the origin. A Van-Vleck paramagnet PrPt$$_5$$ is a typical system of the enhanced nuclear magnetism, which exhibits a ferromagnetic nuclear ordering at $$T_c$$=1.7 mK. This compound has been well characterized and is an ideal system to clarify a relation between the enhanced nuclear magnetism and the anomalous muon spin relaxation in $$^{141}$$Pr-based compounds. We performed $$mu$$SR measurements down to 50 mK. An internal field observed at the muon site is much larger in magnitude than ones due to bare nuclear dipole moments, suggesting an induction of 4$$f$$ magnetic moments. A fluctuation rate $$nu$$ of the field was estimated in the order of a few MHz and the value for $$nu$$ is consistent with one estimated from $$T_c$$. Our observations demonstrate that the $$mu$$SR is an ideal tool to investigate the dynamics of the hyperfine-enhanced nuclear spins in $$f$$ electron systems.

Oral presentation

Possible multipole state of SmRu$$_4$$P$$_{12}$$ probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

no journal, , 

The filled skutterudite compound SmRu$$_4$$P$$_{12}$$ exhibits a metal-insulator (MI) transition at $$T_{rm MI}$$ $$sim$$ 16.5 K. An entropy release $$sim Rln4$$ below $$T_{rm MI}$$ suggests that the crystalline-electric-field ground state is a $$Gamma_{67}$$ quartet with various multipole degrees of freedom. A possibility of magnetic octupole ordering has been intensively discussed to explain the time-reversal-symmetry breaking, anomalous elastic properties, and a complex field-temperature phase diagram. We will report $$mu$$SR measurements on single crystalline samples of SmRu$$_4$$P$$_{12}$$ to investigate the nature of the multipoles in the ordered state. A remarkable longitudinal relaxation was observed in the ordered state, the magnitude of which was reduced below $$T^{prime}$$ $$sim$$ 3 K. We will discuss possible low-energy excitations of magnetic multipoles in the ordered state and their influence on the local magnetic probe on the basis of symmetry of the multipoles.

Oral presentation

Anomalous magnetic state in UPt$$_3$$ at very low temperature

Higemoto, Wataru; Sato, Kazuhiko*; Ito, Takashi; Nishida, Nobuhiko*; Oishi, Kazuki*; Heffner, R. H.; Haga, Yoshinori; Yamamoto, Etsuji; Kimura, Noriaki*; Onuki, Yoshichika; et al.

no journal, , 

The unconventional superconductivity in heavy fermion UPt$$_3$$ attracted much interest. In recent neutron experiment, the narrowing of the AF Bragg peak at low temperature was observed, from which they suggest that a quasistatic AF long range order is realized below 20 mK. We have extended ZF-$$mu$$SR measurement down to 8 mK to investigate the anomalous magnetic state over the very low temperature region. In our ZF-$$mu$$SR, there is no significant change in the muon spinrelaxation rate down to 8 mK. The result suggests the absence of static or quasistaticmagnetic order over the relevant temperature range.

Oral presentation

f-electronic state around an interstitial hydrogen in rare-earth intermetallics

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Aoki, Yuji*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

no journal, , 

no abstracts in English

Oral presentation

Formation of isolated three-spin system Pr-$$mu^+$$-Pr in PrPb$$_3$$

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Nishida, Nobuhiko*; Heffner, R. H.; Aoki, Yuji*; Amato, A.*; Onimaru, Takahiro*; Suzuki, Hiroyuki*

no journal, , 

An isolated few-spin system including a $$mu^+$$ spin $$S$$ is usually unlikely to be realized in metal. Contrary to the expectation, we actually found an isolated three-spin system $$^{141}$$Pr-$$mu^+$$-$$^{141}$$Pr in a rare-earth intermetallic compound PrPb$$_3$$. This system results in $$mu^+$$ spin precession with six frequencies at regular intervals. Such harmonic frequencies cannot be obtained only from dipolar interactions between $$S$$ and bare $$^{141}$$Pr nuclear spins $$I_{141}$$. Extremely anisotropic enhancement of the $$S$$-$$I_{141}$$ coupling is required. This enhancement can be explained by mechanism of the $$^{141}$$Pr hyperfine-enhanced nuclear magnetism and $$mu^+$$-induced perturbation on 4f-electronic state of two Pr ions next to the $$mu^+$$.

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