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Journal Articles

X-ray absorption spectroscopy in the heavy Fermion compound $$alpha$$-YbAlB$$_4$$ at high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11

 Times Cited Count:3 Percentile:31.12(Physics, Multidisciplinary)

Journal Articles

Perturbation on hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics associated with antiferroquadrupolar order in PrV$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Sakai, Akito*; Nakatsuji, Satoru*; Tsujimoto, Masaki*

Physical Review B, 92(12), p.125151_1 - 125151_5, 2015/09

 Times Cited Count:3 Percentile:16.78(Materials Science, Multidisciplinary)

Journal Articles

Large trigonal-field effect on spin-orbit coupled states in a pyrochlore iridate

Uematsu, Daisuke*; Sagayama, Hajime*; Arima, Takahisa*; Ishikawa, Jun*; Nakatsuji, Satoru*; Takagi, Hidenori*; Yoshida, Masahiro*; Mizuki, Junichiro; Ishii, Kenji

Physical Review B, 92(9), p.094405_1 - 094405_6, 2015/09

 Times Cited Count:20 Percentile:67.32(Materials Science, Multidisciplinary)

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state and magnetization in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$) at low temperatures and high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03

 Times Cited Count:1 Percentile:45.76

Valence fluctuation phenomena in rare-earth intermetallic compounds have attracted attention because the quantum criticality of the valence transition has been proposed theoretically. Recently, it was found that $$beta$$-YbAlB$$_4$$ shows quantum criticality without tuning and has a strong mixed-valence state. In this study, we measured the magnetization curve and X-ray magnetoabsorption in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$), which is a locally isostructural polymorph of $$beta$$-YbAlB$$_4$$. The magnetization and X-ray experiments were performed in fields up to 55 and 40 T, respectively. A small increase in the Yb valence was observed at fields where the magnetization curve exhibited a change in slope.

Journal Articles

Magnetic excitations and $$c$$-$$f$$ hybridization effect in PrTi$$_2$$Al$$_{20}$$ and PrV$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*; Harima, Hisatomo*

Physical Review B, 88(8), p.085124_1 - 085124_7, 2013/08

 Times Cited Count:28 Percentile:76.66(Materials Science, Multidisciplinary)

By means of $$^{27}$$Al NMR studies, we have investigated magnetic excitations and the hybridization effect between Pr 4$$f$$ and conduction electrons in a pair of cubic compounds Pr$$Tr$$$$_2$$Al$$_{20}$$ ($$Tr$$=Ti, V). From Knight shift measurements we have evaluated comparative strengths for the $$c$$-$$f$$ hybridization effect in these compounds and confirm a definite increase of hybridization on replacing Ti with V. Analysis of the spin-lattice relaxation rate $$1/T_1$$ reveals that the spectral width of magnetic fluctuations in crystalline electric field excited states is strongly temperature dependent. This result indicates that magnetic fluctuations are dominated by the strong $$c$$-$$f$$ exchange coupling at high temperatures and thus is nicely consistent with the Kondo picture that features ln$$T$$ dependence of resistivity over the same temperature region.

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state in $$alpha$$- and $$beta$$-TbAlB$$_4$$ at low temperature and high magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Kuga, Kentaro*; Nakatsuji, Satoru*; Michimura, Shinji*; Inami, Toshiya; Kawamura, Naomi*; Mizumaki, Masaichiro*

Journal of the Korean Physical Society, 62(12), p.1778 - 1781, 2013/06

 Times Cited Count:9 Percentile:56.19(Physics, Multidisciplinary)

The valence state of Yb ions in $$alpha$$- and $$beta$$-YbAlB$$_4$$ has been investigated by X-ray absorption and emission spectroscopy at temperatures from 2 to 280 K. It is found that the valence gradually increases with increasing temperature toward 3+ and that the characteristic temperature of the valence fluctuations is about 290 K. We also observe a small increase in the Yb valence ($$sim$$ 0.002) in $$beta$$-YbAlB$$_4$$ by a magnetic field of 32 T at 40 K.

Journal Articles

Microscopic evidence for long-range magnetic ordering in the $$Gamma$$$$_{8}$$ ground quartet systems Sm$$Tr$$$$_{2}$$Al$$_{20}$$ ($$Tr$$: Ti, V, Cr)

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB050_1 - SB050_4, 2012/12

Recently, $$RT_2$$Al$$_{20}$$ compounds ($$R$$: rare earth, $$T$$: transition metal) have attracted much attention due to interesting physical properties closely related to their caged-structure. Each $$R$$ ion is confined in a Frank-Kasper cage consisting of 16 Al atoms and the large coordination number leads to strong $$c$$-$$f$$ hybridization. In addition, the Frank-Kasper cage allows various multipole degrees of freedom for the $$f$$-electrons at low $$T$$ because of a highly symmetric crystalline-electric-field (CEF). Among the $$RT_2$$Al$$_{20}$$ series, Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) exhibit both these features. The $$Gamma_3$$ ground doublet systems Pr$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V) show a phase transition at $$T_O$$ = 2.0K (Ti) and 0.6K (V). The order parameter is believed to be an electric quadrupole active in the $$Gamma_3$$ subspace. A possibility of the quadrupole Kondo effect has been discussed based on characteristic $$T$$-dependence in specific heat, resistivity, and magnetic susceptibility. The $$Gamma_8$$ ground quartet systems Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) also exhibit a phase transition at $$T_O$$ = 6.4K (Ti), 2.3K (V), and 1.8K (Cr). A nuclear specific heat study in SmTi$$_2$$Al$$_{20}$$ suggests that the primary order parameter is a magnetic dipole in spite of field-insensitive nature of the phase boundary. A possible importance of a secondarily ordered octupole moment was discussed. We here present a microscopic study of PrTi$$_2$$Al$$_{20}$$ and Sm$$T_2$$Al$$_{20}$$ ($$T$$: Ti, V, Cr) using muon spin relaxation. In PrTi$$_2$$Al$$_{20}$$, no additional local field was observed in the ordered phase. This strongly supports the quadrupole ordering scenario. On the other hand, an appearance of a coherent local field was observed below $$T_O$$ in Sm$$T_2$$Al$$_{20}$$. This is consistent with the primary magnetic dipole ordering. The frequency distribution suggests that the magnetic structure is possibly different between the Sm$$T_2$$Al$$_{20}$$ compounds.

Journal Articles

Spin-orbital short-range order on a honeycomb-based lattice

Nakatsuji, Satoru*; Kuga, Kentaro*; Kimura, Kenta*; Satake, Ryuta*; Katayama, Naoyuki*; Nishibori, Eiji*; Sawa, Hiroshi*; Ishii, Rieko*; Hagiwara, Masayuki*; Bridges, F.*; et al.

Science, 336(6081), p.559 - 563, 2012/05

 Times Cited Count:108 Percentile:95.76(Multidisciplinary Sciences)

Frustrated magnetic materials can remain disordered to the lowest temperatures. Such is the case for Ba$$_3$$CuSb$$_2$$O$$_9$$, which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu$$^{2+}$$ ions that resists a coherent static Jahn-Teller distortion. The resulting two-dimensional random-bond spin-1/2 system on the honeycomb lattice has a broad spectrum of spin-dimer like excitations and low-energy spin degrees of freedom that retain.

Journal Articles

$$mu$$SR evidence of nonmagnetic order and $$^{141}$$Pr hyperfine-enhanced nuclear magnetism in the cubic $$Gamma_3$$ ground doublet system PrTi$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Luetkens, H.*; Baines, C.*; Sakai, Akito*; Nakatsuji, Satoru*

Journal of the Physical Society of Japan, 80(11), p.113703_1 - 113703_4, 2011/11

 Times Cited Count:28 Percentile:79.07(Physics, Multidisciplinary)

Oral presentation

NMR study of PrTi$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Saito, Yo; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

$$mu$$SR studies of $$RTr_2$$Al$$_{20}$$ ($$R$$: Pr, Sm, $$Tr$$: Ti, V, Cr) with a cage structure

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

$$mu$$SR study of PrTi$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

Al-NMR study of PrTi$$_2$$Al$$_{20}$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

Al-NMR study of PrTi$$_2$$Al$$_{20}$$, 2

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

Oral presentation

NMR study of Pr$$T_2$$Al$$_{20}$$ ($$T$$=Ti, V)

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

In this study, we have performed $$^{27}$$Al NMR/NQR measurements for Pr$$T_2$$Al$$_{20}$$ ($$T$$=Ti, V). $$^{27}$$Al NMR spectra have been measured in a temperature range between 1.4 and 300 K, and the temperature dependence of the Knight shift $$K$$ has been extracted for Al(2) and Al(3). Then, from the so-called $$K$$ vs $$chi$$ plot, the hyperfine coupling constants ($$A_{hf}$$) has been estimated for each site in each compound. A large $$A_{hf}$$ obtained for Al(3) indicates the strong hybridization between Pr and Al-cage. In addition, the stronger hybridization in PrV$$_2$$Al$$_{20}$$ than in PrTi$$_2$$Al$$_{20}$$ is confirmed from the $$A_{hf}$$ values.

Oral presentation

Magnetic properties of the spinel AYb$$_2$$S$$_4$$ (A = Cd, Mg) probed by $$mu$$SR

Higemoto, Wataru; Ito, Takashi; Koda, Akihiro*; Iritani, Kenshi*; Halim, M.*; Nakatsuji, Satoru*

no journal, , 

Varieties of magnetic states are seen in spinel structural magnets due to spin frustration effect. In particular, much attention is paid on recent study on pyrochlore structural magnet with rare-earth elements because interesting spin state, spin ice or other state, is observed. We have studied on spinel magnet AYb$$_2$$S$$_4$$ to clarify the magnetic ground state by means of muon spin relaxation method. In our measurement, static magnetic ordering state was clearly observed.

Oral presentation

Magnetic properties of the spinel AYb$$_2$$Se$$_4$$ (A=Cd, Mg) probed by $$mu$$SR

Higemoto, Wataru; Ito, Takashi; Iritani, Kenshi*; Halim, M.*; Nakatsuji, Satoru*

no journal, , 

A spinel structural system shows a variety of the magnetic state due to its frustration effect. Up to now, we have studied the magnetic ground state of spinel structural system AYb$$_2$$S$$_4$$(A=Cd, Mg) by using muon spin relaxation method and observed the appearance of the magnetic ordering state below 2K in CdYb$$_2$$S$$_4$$ and 1.5K in MgYb$$_2$$S$$_4$$. For systematic study of the frustration effect, we are measuring muon spin relaxation in same structural compounds AYb$$_2$$Se$$_4$$ (A=Cd, Mg). In CdYb$$_2$$Se$$_4$$, the local magnetic field was observed below 2K. In the presentation, we will discuss the detail of the magnetic state.

Oral presentation

Muon spin relaxation in PrV$$_2$$Al$$_{20}$$

Ito, Takashi; Higemoto, Wataru; Sakai, Akito*; Nakatsuji, Satoru*

no journal, , 

no abstracts in English

18 (Records 1-18 displayed on this page)
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