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Journal Articles

Magnetic-ordering propagation vectors of terbium hexaboride revisited

Iwasa, Kazuaki*; Iga, Fumitoshi*; Moyoshi, Taketo*; Nakao, Akiko*; Ohara, Takashi

Journal of the Physical Society of Japan, 87(6), p.064705_1 - 064705_5, 2018/06

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Journal Articles

Large ferroquadrupole moment induced in the octupole-ordered Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ revealed by high-resolution X-ray diffraction

Inami, Toshiya; Michimura, Shinji*; Hayashi, Yuya*; Matsumura, Takeshi*; Sera, Masafumi*; Iga, Fumitoshi*

Physical Review B, 90(4), p.041108_1 - 041108_5, 2014/07

 Times Cited Count:8 Percentile:55.57(Materials Science, Multidisciplinary)

We carried out a high-resolution X-ray diffraction experiment on Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$. This compound exhibits antiferro-octupole order (AFO) below $$T_O$$ = 1.4 K, and it is theoretically suggested that ferroquadrupole moments and a resultant rhombohedral deformation are induced in the AFO phase. We observe the splitting of Bragg reflections below $$T_O$$ and find that the unit cell is rhombohedral with the elongated [111] axis. We also precisely evaluate the magnitude of the induced quadrupole moments from the obtained shear strain and find that the quadrupole moments are not reduced in the AFO phase.

Journal Articles

Multipole order and fluctuation in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ studied by resonant X-ray diffraction

Matsumura, Takeshi*; Michimura, Shinji*; Inami, Toshiya; Otsubo, Toru*; Tanida, Hiroshi*; Iga, Fumitoshi*; Sera, Masafumi*

JPS Conference Proceedings (Internet), 3, p.014008_1 - 014008_6, 2014/06

We study the $$T_{beta}$$-type antiferro-octupole (AFO) ordered state of Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ below 1.5 K by resonant X-ray diffraction in magnetic fields. Multipole moments induced by the field in the AFO phase are identified. In a mean-field model for the $$T_{beta}$$ AFO order within the $$Gamma_8$$ quartet crystal-field ground state, the $$O_{22}$$ and $$O_{20}$$ antiferroquadrupoles (AFQ) are expected as mostly induced AFQ. However, in contrast to this expectation, the main induced moment is found to be the $$O_{xy}$$-type AFQ.

Journal Articles

Synchrotron radiation-based M$"o$ssbauer spectra of $$^{174}$$Yb measured with internal conversion electrons

Masuda, Ryo*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Kurokuzu, Masayuki*; Saito, Makina*; Yoda, Yoshitaka*; Mitsui, Takaya; Iga, Fumitoshi*; Seto, Makoto

Applied Physics Letters, 104(8), p.082411_1 - 082411_5, 2014/02

 Times Cited Count:9 Percentile:51.77(Physics, Applied)

A detection system for synchrotron-radiation (SR)-based M$"o$ssbauer spectroscopy was developed to enhance the nuclear resonant scattering counting rate and thus increase the available nuclides. In the system, a windowless avalanche photodiode (APD) detector was combined with a vacuum cryostat to detect the internal conversion (IC) electrons and fluorescent X-rays accompanied by nuclear de-excitation. As a feasibility study, the SR-based M$"o$ssbauer spectrum using the 76.5 keV level of $$^{174}$$Yb was observed without $$^{174}$$Yb enrichment of the samples. The counting rate was five times higher than that of our previous system, and the spectrum was obtained within 10 h. This result shows that nuclear resonance events can be more efficiently detected by counting IC electrons for nuclides with high IC coefficients. Furthermore, the windowless detection system enables us to place the sample closer to the APD elements and is advantageous for nuclear resonant inelastic scattering measurements. Therefore, this detection system can not only increase the number of nuclides accessible in SR-based M$"o$ssbauer spectroscopy but also allows the nuclear resonant inelastic scattering measurements of small single crystals or enzymes with dilute probe nuclides that are difficult to measure with the previous detection system.

Journal Articles

Evidence for hidden quadrupolar fluctuations behind the octupole order in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ from resonant X-ray diffraction in magnetic fields

Matsumura, Takeshi*; Michimura, Shinji*; Inami, Toshiya; Otsubo, Toru*; Tanida, Hiroshi*; Iga, Fumitoshi*; Sera, Masafumi*

Physical Review B, 89(1), p.014422_1 - 014422_13, 2014/01

 Times Cited Count:11 Percentile:45.03(Materials Science, Multidisciplinary)

The multipole ordered phase in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ (phase IV) has been studied by resonant X-ray diffraction in magnetic fields. By utilizing diamond X-ray phase plates to rotate the incident linear polarization and a conventional crystal analyzer system, full linear polarization analysis has been performed to identify the order parameters. The analysis shows that the $$Gamma_{rm 5g}$$ quadrupoles are more induced by the field than the $$Gamma_{rm 3g}$$ quadrupoles in phase IV, in disagreement with mean-field calculations, in which the $$Gamma_{rm 3g}$$ quadrupole is the main induced moment. Hence, we consider that large fluctuations of the $$Gamma_{rm 5g}$$ quadrupole is hidden behind the primary ordering of the octupole.

Journal Articles

Application of miniature pulsed magnets to synchrotron X-ray spectroscopy and neutron diffraction

Matsuda, Yasuhiro*; Murata, Yuto*; Inami, Toshiya; Owada, Kenji; Nojiri, Hiroyuki*; Oyama, Kenji*; Kato, Naoki*; Murakami, Yoichi*; Iga, Fumitoshi*; Takabatake, Toshiro*; et al.

Journal of Physics; Conference Series, 51, p.490 - 493, 2006/00

 Times Cited Count:7 Percentile:8.19

Journal Articles

Search for orbital excitation in YTiO$$_3$$ by neutron scattering

Shamoto, Shinichi; Tsubota, Masami*; Iga, Fumitoshi*; F${aa}$k, B.*; Kajitani, Tsuyoshi*

Journal of Neutron Research, 13(1-3), p.175 - 178, 2005/03

YTiO$$_3$$ with T$$_c$$~30 K has been studied by the MARI spectrometer with E$$_i$$=130 meV and 500 meV at T=5 K, 40K, and 200 K. We have not found any clear orbital excitation in a wide Q-E range (0.5$$<$$Q$$<$$25$AA $^{-1}$$, 6$$<$$E$$<$$350 meV). The intensity of orbital excitation would be significantly weak in comparison with the phonon.

Journal Articles

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

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

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

 Times Cited Count:18 Percentile:31.79(Physics, Condensed Matter)

no abstracts in English

Oral presentation

$$mu$$SR study of cubic $$Gamma_8$$ ground state system DyB$$_6$$

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Iga, Fumitoshi*

no journal, , 

no abstracts in English

Oral presentation

$$mu$$SR study of the cubic $$Gamma_8$$ ground state system DyB$$_6$$, 2

Ito, Takashi; Higemoto, Wataru; Ninomiya, Kazuhiko; Iga, Fumitoshi*

no journal, , 

no abstracts in English

Oral presentation

Resonant X-ray diffraction study of Ce$$_{0.7}$$La$$_{0.3}$$B$$_{6}$$ in magnetic field

Michimura, Shinji; Inami, Toshiya; Otsubo, Toru*; Matsumura, Takeshi*; Tanida, Hiroshi*; Sera, Masafumi*; Iga, Fumitoshi*

no journal, , 

no abstracts in English

Oral presentation

Magnetic ordering in Tm$$_{1-x}$$Yb$$_x$$B$$_6$$

Higemoto, Wataru; Ito, Takashi; Ninomiya, Kazuhiko; Iga, Fumitoshi*; Fukuta, Kenji*; Takabatake, Toshiro*

no journal, , 

It is well known that RB$$_6$$ (R: rear-earth element) exhibit variety of properties. For example, CeB$$_6$$ is considered as a typical compound of Kondo lattice system and many studies have been carried out from the viewpoints of multipole ordering etc. TmB$$_6$$ is interesting compound due to its possible valence fluctuation. However, material synthesis have not been reported yet. Mean while, YnB$$_6$$ shows non magnetic ground state. We have carried out muon spin relaxation ($$mu$$SR) measurements in polycrystalline specimen of Tm$$_{0.55}$$Yb$$_{0.45}$$B$$_6$$ to elucidate magnetic ground state. As a result, we have clearly observed local magnetic field below 2K and evidently, whole the system is in magnetic ordering state.

Oral presentation

Rhombohedral deformation of Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ observed by high-resolution X-ray diffraction

Inami, Toshiya; Michimura, Shinji*; Hayashi, Yuya*; Matsumura, Takeshi*; Sera, Masafumi*; Iga, Fumitoshi*

no journal, , 

no abstracts in English

Oral presentation

Rhombohedral deformation in the phase IV of Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ observed by high-resolution X-ray diffraction

Inami, Toshiya; Michimura, Shinji*; Hayashi, Yuya*; Matsumura, Takeshi*; Sera, Masafumi*; Iga, Fumitoshi*

no journal, , 

no abstracts in English

Oral presentation

High-resolution X-ray diffraction experiment on the octupole ordered phase in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$

Inami, Toshiya; Michimura, Shinji*; Matsumura, Takeshi*; Hayashi, Yuya*; Sera, Masafumi*; Iga, Fumitoshi*

no journal, , 

We have carried out a high-resolution X-ray diffraction experiment at low temperatures and in magnetic fields on Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ that exhibits antiferrooctupole (AFO) order below $$T_O$$=1.4K. Ferroquadrupole moments that accompany the AFO order and a resultant rhombohedral deformation of the cubic lattice were theoretically predicted and experimetanlly supported. However, the sign and magnitude of the rhombohedral deformation have not yet been determined. We observe the splitting of Bragg peaks below $$T_O$$, which is consistent with a rhombohedral deformation of 4$$times10^{-5}$$ elongated along the [111] axis. The response of rhombohedral domains to magnetic fields also well agrees with theoretical calculations. A particular outcome of this experiment is that the magnitude of the induced quadrupole moments is precisely evaluated from the obtained shear strain.

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