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Journal Articles

Nature of structural instabilities in superconducting Sr$$_3$$Ir$$_4$$Sn$$_{13}$$

Kaneko, Koji; Cheung, Y. W.*; Hu, Y.*; Imai, Masaki*; Tanioku, Yasuaki*; Kanagawa, Hibiki*; Murakawa, Joichi*; Moriyama, Kodai*; Zhang, W.*; Lai, K. T.*; et al.

JPS Conference Proceedings (Internet), 30, p.011032_1 - 011032_6, 2020/03

Journal Articles

Evidence of a structural quantum critical point in (Ca$$_x$$Sr$$_{1-x}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$ from a lattice dynamics study

Cheung, Y. W.*; Hu, Y. J.*; Imai, Masaki*; Tanioku, Yasuaki*; Kanagawa, Hibiki*; Murakawa, Joichi*; Moriyama, Kodai*; Zhang, W.*; Lai, K. T.*; Yoshimura, Kazuyoshi*; et al.

Physical Review B, 98(16), p.161103_1 - 161103_5, 2018/10

 Times Cited Count:4 Percentile:50.71(Materials Science, Multidisciplinary)

Journal Articles

Occupation sites and valence states of Co dopants in (La, Co)-codoped M-type Sr ferrite; $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance studies

Sakai, Hironori; Hattori, Taisuke; Tokunaga, Yo; Kambe, Shinsaku; Ueda, Hiroaki*; Tanioku, Yasuaki*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Takao, Kenta*; Shimoda, Aiko*; et al.

Physical Review B, 98(6), p.064403_1 - 064403_10, 2018/08

 Times Cited Count:5 Percentile:50.71(Materials Science, Multidisciplinary)

To specify preferential occupation sites of Co substituents and to clarify charge and spin states of Co ions in (La, Co)-cosubstituted hexagonal magnetoplumbite-type (M-type) Sr ferrite, $$^{57}$$Fe and $$^{59}$$Co nuclear magnetic resonance (NMR) spectra are measured under zero and external magnetic fields using powdered and single crystalline specimens. To a considerable degree, the charge compensation between La$$^{3+}$$ and Co$$^{2+}$$ works in the equal (La, Co)-codoped case, where more than half of the Co ions are considered to be present in the minority spin $$4f_1$$ sites at the center of the oxygen tetrahedra, with the $$S$$ = 3/2 state carrying a small orbital moment owing to spin-orbit interaction. The remaining small number of high-spin Co$$^{2+}$$ ($$S$$ = 3/2, $$L$$ = 1) ions with unquenched orbital moments would be distributed to the other octahedral $$12k$$, $$2a$$, and $$4f_2$$ sites.

Journal Articles

Second-order structural transition in (Ca$$_{0.5}$$Sr$$_{0.5}$$)$$_3$$Rh$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Hu, Y. J.*; Goh, S. K.*; Kaneko, Koji; Tsutsui, Satoshi; Logg, P. W.*; Grosche, F. M.*; Kanagawa, Hibiki*; Tanioku, Yasuaki*; Imai, Masaki*; et al.

Journal of Physics; Conference Series, 807(3), p.032002_1 - 032002_4, 2017/04


 Times Cited Count:3 Percentile:12.9

Journal Articles

NMR investigation of spin fluctuations in the itinerant-electron magnetic compound $${rm Sr}_{1-x}{rm Ca}_x{rm Co}_2{rm P}_2$$

Imai, Masaki; Michioka, Chishiro*; Ueda, Hiroaki*; Yoshimura, Kazuyoshi*

Physical Review B, 95(5), p.054417_1 - 054414_7, 2017/02

 Times Cited Count:1 Percentile:88.65(Materials Science, Multidisciplinary)

We took $$^{31}$$P NMR measurements of mainly paramagnetic phase $${rm Sr}_{1-x}{rm Ca}_x{rm Co}_2{rm P}_2$$ to reveal the itinerant-electron metamagnetic transition, and of its magnetically ordered phase, and characterized their spin fluctuations by estimating the spin fluctuation parameter $$T_{0}$$ corresponding to the width of the spin fluctuation in the spectrum in frequency space. As $$x$$ increases from 0 to 0.5, the in-plane component of $$T_{0}$$ decreases proportionally with the metamagnetic transition field. In the antiferromagnetic cT phase, $$T_{0}$$ is constant and spin fluctuations show an isotropic character in contrast to their behavior in the paramagnetic ucT phase. These results indicate that the in-plane spin fluctuations due to the quasi-two-dimensional crystal structure play a significant role in the metamagnetic transition of this system.

Journal Articles

Second-order structural transition in the superconductor La$$_3$$Co$$_4$$Sn$$_{13}$$

Cheung, Y. W.*; Zhang, J. Z.*; Zhu, J. Y.*; Yu, W. C.*; Hu, Y. J.*; Wang, D. G.*; Otomo, Yuka*; Iwasa, Kazuaki*; Kaneko, Koji; Imai, Masaki*; et al.

Physical Review B, 93(24), p.241112_1 - 241112_5, 2016/06


 Times Cited Count:12 Percentile:32.31(Materials Science, Multidisciplinary)

Journal Articles

Observation of the partial Fermi surface quenching in the noncentrosymmetric superconductor Mo$$_3$$Al$$_2$$C

Koyama, Takehide*; Ozaki, Yuzuru*; Ueda, Koichi*; Mito, Takeshi*; Kohara, Takao*; Waki, Takeshi*; Tabata, Yoshikazu*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Suzuki, Michito; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB008_1 - SB008_5, 2012/12

 Times Cited Count:1 Percentile:87.6(Physics, Multidisciplinary)

The normal state properties of a noncentrosymmetric superconductor Mo$$_3$$Al$$_2$$C are studied by means of the nuclear magnetic resonance (NMR) experiment. The change of NMR line shape and the peak of the nuclear spin-echo decay rate at $$simeq$$ 130 K indicate that the Mo$$_3$$Al$$_2$$C exhibits the phase transition prior to the emergence of superconductivity. The reduction in the conduction electron density is inferred from the decrease in the nuclear spin-lattice relaxation rate. The nature of the newly found phase transition is discussed by considering the result of the first principle calculations, indicating a good nesting property of the Fermi surfaces.

Journal Articles

High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

Nakamura, Toshiyuki*; Matsuda, Yasuhiro*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 Times Cited Count:11 Percentile:37.32(Physics, Multidisciplinary)

The X-ray absorption and magnetic circular dichroism (MCD) spectra at the Yb L$$_3$$ edge were measured in the mixed-valent heavy fermion compound YbAgCu$$_4$$ at high magnetic fields and low temperatures. The magnetic-field-temperature (H-T) phase boundary determined by the valence state is in very good agreement with that determined by the magnetization. It is clearly found that the metamagnetism of this compound is due to the field induced valence transition. A distinctive positive peak of the XMCD spectra appears in the vicinity of the white line of the absorption due to Yb$$^{3+}$$ state, while no feature is observed in the XMCD spectra corresponding to the Yb$$^{2+}$$ state. A small negative XMCD peak was observed at a lower energy and was attributed to the quadrupole trasition from theoretical calcuration, which explains its peculicar magnetic field dependence.

Journal Articles

Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 Times Cited Count:10 Percentile:39.54(Physics, Multidisciplinary)

The valence change of Yb ion in YbAgCu$$_4$$ was measured by means of X-ray absorption spectroscopy under high magnetic fields up to 35T. The valence state of Yb in YbAgCu$$_4$$ at 4.8K significantly increases at the metamagnetic transition. The saturation value of $$v$$ at 55T is evaluated as 2.97 using the relation $$Delta M/Delta v$$ at 35T. This value is in good agreement with $$v$$ for the related compound YbInCu$$_4$$ at high temperatures and the Yb valence in the localized high-field phase. We conclude that the metamagnetic transition in YbAgCu$$_4$$ arises from the valence transition, as theoretically predicted.

Journal Articles

Partial gap opening on the Fermi surface of the noncentrosymmetric superconductor Mo$$_3$$Al$$_2$$C

Koyama, Takehide*; Ozaki, Yuzuru*; Ueda, Koichi*; Mito, Takeshi*; Kohara, Takao*; Waki, Tsuyoshi*; Tabata, Yoshikazu*; Michioka, Chishiro*; Yoshimura, Kazuyoshi*; Suzuki, Michito; et al.

Physical Review B, 84(21), p.212501_1 - 212501_4, 2011/12

 Times Cited Count:9 Percentile:55.32(Materials Science, Multidisciplinary)

The results of $$^{27}$$Al nuclear magnetic resonance and specific-heat measurements of the noncentrosymmetric superconductor Mo$$_3$$Al$$_2$$C are reported. The phase transition around 130 K is inferred from a distinct change in the NMR spectrum, a clear peak in the spin-echo decay rate, and an anomaly in the specific heat. Possibility of charge-density wave ordering around 130 K is discussed by calculating the Fermi surfaces in the normal states and considering the partial quenching of the Fermi surfaces with the decrease in 1/$$T$$$$_1$$ below the superconducting transition temperature.

Journal Articles

Magnetic excitations in infinite-layer antiferromagnetic insulator

Tomiyasu, Keisuke*; Kageyama, Hiroshi*; Lee, C.*; Whangbo, M. H.*; Tsujimoto, Yoshihiro*; Yoshimura, Kazuyoshi*; Taylor, J. W.*; Llobet, A.*; Trouw, F.*; Kakurai, Kazuhisa; et al.

Journal of the Physical Society of Japan, 79(3), p.034707_1 - 034707_4, 2010/03

 Times Cited Count:14 Percentile:32.76(Physics, Multidisciplinary)

Journal Articles

XMCD spectroscopy on valence fluctuating and heavy fermion compounds in very high magnetic fields up to 40 T

Matsuda, Yasuhiro*; Her, J. L.*; Inami, Toshiya; Owada, Kenji; Ouyang, Z. W.*; Okada, Kyoko*; Nojiri, Hiroyuki*; Mitsuda, Akihiro*; Wada, Hirofumi*; Yoshimura, Kazuyoshi*; et al.

Journal of Physics; Conference Series, 190, p.012019_1 - 012019_6, 2009/11

 Times Cited Count:7 Percentile:12.32

Journal Articles

High-magnetic-field X-ray absorption spectroscopy of field-induced valence transition in YbInCu$$_4$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*

Journal of the Physical Society of Japan, 76(3), p.034702_1 - 034702_6, 2007/03

 Times Cited Count:50 Percentile:13.09(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Photoemission spectroscopy and X-ray absorption spectroscopy studies of the superconducting pyrochlore oxide Cd$$_{2}$$Re$$_{2}$$O$$_{7}$$

Irizawa, Akinori*; Higashiya, Atsushi*; Kasai, Shuichi*; Sasabayashi, Takehisa*; Shigemoto, Akihiko*; Sekiyama, Akira*; Imada, Shin*; Suga, Shigemasa*; Sakai, Hironori; Ono, Hiroyuki*; et al.

Journal of the Physical Society of Japan, 75(9), p.094701_1 - 094701_5, 2006/09

 Times Cited Count:6 Percentile:55.89(Physics, Multidisciplinary)

Photoemission spectroscopy (PES) and O $$1s$$ X-ray absorption spectroscopy (XAS) measurements have been performed for Cd$$_2$$ Re$$_2$$ O$$_7$$ single crystals. Temperature variations of their spectra reveal that the phase transition at 120 K directly changes the band structure near the Fermi level compared with another transition near 200 K. The roles of the transitions are discussed in terms of the changes in the Re-O orbital hybridization.

Journal Articles

Spin gap in Tl$$_2$$Ru$$_2$$O$$_7$$ and the possible formation of Haldane chains in three-dimensional crystals

Lee, S.*; Park, J.-G.*; Adroja, D. T.*; Khomskii, D.*; Streltsov, S.*; McEwen, K. A.*; Sakai, Hironori; Yoshimura, Kazuyoshi*; Anisimov, V. I.*; Mori, Daisuke*; et al.

Nature Materials, 5(6), p.471 - 476, 2006/06

 Times Cited Count:94 Percentile:5.52(Chemistry, Physical)

Here we show that the three-dimensional cubic system of Tl$$_2$$Ru$$_2$$O$$_7$$ most probably evolves into a one-dimensional spin-one Haldane system with a spin gap below 120 K, accompanied by anomalies in the structure, resistivity, and susceptibility. We argue that these anomalies are due to an orbital ordering of Ru $$4d$$ electrons, with a strong coupling among three degrees of freedom: orbital, spin, and lattice. Our work provides a unique example of the spontaneous formation of Haldane system with an insight into the intriguing interplay of different degrees of freedom.

Journal Articles

High field X-ray diffraction study on a magnetic-field-induced valence transition in YbInCu$$_4$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*

Journal of the Physical Society of Japan, 75(2), p.024710_1 - 024710_5, 2006/02

 Times Cited Count:38 Percentile:17.12(Physics, Multidisciplinary)

We report the first high-field X-ray diffraction experiment using synchrotron X-rays and pulsedmagnetic fields exceeding 30 T. The lattice deformation due to a magnetic-field-induced valencetransition in YbInCu$$_4$$ is studied. It has been found that the Bragg reflection profile at 32K changessignificantly at around 27 T due to the structural transition. In the vicinity of the transition field, the lowfield and high field phases alternate with the discontinuous change in the lattice constant. Thus, it isevident that the field-induced valence state transition is a first-order phase transition. The fielddependence of the low-field-phase Bragg peak intensity is found to be roughly scaled with themagnetization.

Journal Articles

X-ray diffraction experiments under pulsed magnetic fields above 30T

Inami, Toshiya; Owada, Kenji; Matsuda, Yasuhiro*; Ueda, Yuji*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Arima, Takahisa*; Ota, Hiroto*; Zhang, W.*; Yoshimura, Kazuyoshi*

Nuclear Instruments and Methods in Physics Research B, 238(1-4), p.233 - 236, 2005/08

 Times Cited Count:8 Percentile:44.75(Instruments & Instrumentation)

Usually, X-ray diffraction experiments under strong magnetic fields are carried out using a superconducting magnet and the maximum field is limited up to 15T. In order to overcome this limitation, we have constructed an X-ray diffraction system combined with a pulsed magnet. The structural phase transition of Pr$$_{0.6}$$Ca$$_{0.4}$$MnO$$_3$$ around 8 T and the valence transition of YbInCu$$_4$$ around 26 T are shown as a demonstration.

Journal Articles

Decrease in $$^{111}$$Cd knight shift in superconducting Cd$$_{2}$$Re$$_{2}$$O$$_{7}$$; Evidence for spin-singlet pairing

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Kitagawa, Kentaro*; Murakawa, Hiroshi*; Ishida, Kenji*; Ono, Hiroyuki*; Kato, Masaki*; Yoshimura, Kazuyoshi*; Walstedt, R. E.

Journal of the Physical Society of Japan, 73(11), p.2940 - 2943, 2004/11

 Times Cited Count:4 Percentile:66.45(Physics, Multidisciplinary)

$$^{111}$$Cd NMR measurements have been performed in the superconducting (SC) state of the pyrochlore Cd$$_{2}$$Re$$_{2}$$O$$_{7}$$ at T$$_{c}$$ $$sim$$ 1 K, and in a field of less than 3 kOe below $$T_{c}$$. The upper critical field at 0.1 K has been determined to be 4 kOe from in situ measurements of the ac susceptibility. A reduction of the Knight shift in the SC state is confirmed. The present results provide strong evidence that this compound has a singlet SC pairing symmetry.

Journal Articles

Synthesis and physical properties of pyrochlore iridium oxides Pb$$_{2-x}$$Ca$$_{x}$$Ir$$_{2}$$O$$_{7-y}$$

Sakai, Hironori; Ono, Hiroyuki*; Oba, Noriaki*; Kato, Masaki*; Yoshimura, Kazuyoshi*

Physica B; Condensed Matter, 329-333(2), p.1038 - 1039, 2003/05

 Times Cited Count:2 Percentile:83.87

Pyrochlore iridium oxides Pb$$_{2-x}$$Ca$$_{x}$$Ir$$_{2}$$O$$_{7-y}$$ ($$x$$=0.0, 0.2, 0.4, 0.6, 0.8) were prepared by solid state reaction. The electrical resistivity and the magnetic susceptibility were measured between 4.2 and 300 K. These compounds show metallic conductivity and obey the Curie-Weiss law with temperature independent term. The metallic conductivity of Pb$$_{2}$$Ir$$_{2}$$O$$_{7}$$ is suppressed by the Ca substitution for Pb site.

Journal Articles

Systematic evolution of the Kondo peak in YbCu$$_{5-x}$$Ag$$_{x}$$

Okane, Tetsuo; Fujimori, Shinichi; Mamiya, Kazutoshi; Okamoto, Jun; Fujimori, Atsushi; Tsujii, Naoto*; Yoshimura, Kazuyoshi*

Acta Physica Polonica B, 34(2), p.1019 - 1022, 2003/02

no abstracts in English

25 (Records 1-20 displayed on this page)