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  2. Goto Takayuki

Goto Takayuki

  (後藤 貴行)

Profile Information

Affiliation
Professor, Faculty of Science and Technology, Department of Engineering and Applied Sciences, Sophia University
Degree
理学博士(東京大学)
Contact information
gotoo-tsophia.ac.jp
Researcher number
90215492
J-GLOBAL ID
200901036665053574
researchmap Member ID
1000004658

In the graduate days, worked on the quantum size effect in small metal particles of nano-size, for which the discreteness in the energy levels of conduction electrons was successfully observed in the dilution temperature region below few tens milli-Kelvin.

Since 1989, started working in the laboratory of low temperature physics in Institute for Materials Research at Tohoku University, as a research staff, where I had built three sets of NMR spectrometers, by which high-TC cuprates and organic conductors were studied. I had revealed that
the universal electronic phase diagram for high-TC cuprates holds for Tl-based cuprate.
I found the first evidence that the non-doped Tl-based cuprate is antiferromagnetism, and that
the characteristic energy of spin fluctuation in the antiferromagnetic region possibly determines TC.

In 1998, moved on to Sophia Univ. as an associate professor, where I started up the laboratory for low-temperature physics. The research area was expanded to other exotic matters such as low dimensional quantum spin magnets, and organic metals.　From 2004, a new technique of muSR in collaboration with RIKEN-RAL and PSI was adopted and applied to quantum spin systems.

Lectures and experiments: Statistical Physics II, Analytical Mechanics, Experimental Physics ("magnetic resonance"), Exercise for Quantum Mechanics, Physics Experiments I, Physics Experiments III, Condensed matter physics.
Current research themes are NMR study on quantum spin magnet, high-Tc cuprates and orgamic metals in low temperatures and high magnetic field.

(Subject of research)
NMR and muSR study on high-Tc cuprates and low dimensional quantum spin systems.

Research Interests

 3

Research Areas

 1

Research History

 5

Committee Memberships

 1

Awards

 1

Papers

 220
  • Takayuki Goto, Takeshi Hashimoto, Kai Sato, Yukihiro Kitamoto, Takashi Hayashita, Satoshi Iguchi, Takahiko Sasaki, Dita Puspita Sari, Isao Watanabe
    Journal of the Physical Society of Japan, 92(12), Dec 15, 2023  Peer-reviewed
  • Iori Nishizawa, Nobuyuki Kurita, Hidekazu Tanaka, Takayuki Goto
    Physical Review B, 107(17), May 12, 2023  Peer-reviewed
  • Masari Watanabe, Nobuyuki Kurita, Hidekazu Tanaka, Wataru Ueno, Kazuki Matsui, Takayuki Goto, Masato Hagihala
    Physical Review B, 105(5), Feb 1, 2022  Peer-reviewed
    We report the magnetic properties of the double perovskites SrLaCuSbO6 (SLCSO) and SrLaCuNbO6 (SLCNO). The temperature dependence of the magnetic susceptibilities of both compounds shows a broad maximum characteristic of an S=1/2 square lattice Heisenberg antiferromagnet. Magnetic ordering occurs at TN=13.6 and 15.7 K for SLCSO and SLCNO, respectively. Neutron powder diffraction measurements reveal contrasting spin structures in both compounds. The spin structures of SLCSO and SLCNO below TN are Néel antiferromagnetic and columnar antiferromagnetic, respectively. This result demonstrates that the nearest-neighbor interaction is dominant in SLCSO, whereas the next-nearest-neighbor interaction is dominant in SLCNO. The magnitude of the ordered moment was evaluated at 3.5 K to be m=0.39(3)μB for SLCSO and 0.37(1)μB for SLCNO, which are significantly smaller than those calculated using linear spin wave theory. We infer that the small ordered moment is caused by the effect of bond randomness arising from the site disorder of Sr and La ions.
  • Suci Winarsih, Faisal Budiman, Hirofumi Tanaka, Tadashi Adachi, Takayuki Goto, Bambang Soegijono, Budhy Kurniawan, Isao Watanabe
    Key Engineering Materials, 860 142-147, Aug 1, 2020  Peer-reviewed
    We report the results of the resistivity measurement on La2-xSrxCuO4 nanoparticles with x = 0, 0.05, and 0.20 evaluated by the four-point probe method. The high resistivity value shows the predominance of the inter-grain part. The temperature dependence of the conductivity can be analyzed by variable range hopping model showing the charge carriers are formed by thermal activation. There is no superconducting behavior that could be observed in La2-xSrxCuO4 nanoparticles with x = 0.05 and 0.20.
  • Takumi Kusakawa, Takayuki Goto, Akiko Hori
    CrystEngComm, 22(18) 3090-3094, Apr 27, 2020  Peer-reviewed
    Expanded p-conjugated coordination complexes, [M(L2)2] (M = Cu2+, Pd2+, and Pt2+; L2= dinaphthoylmethanido-), were prepared and the different metal characteristics were found due to the supramolecular associations: [Cu(L2)2] shows a remarkable M2+?p interaction (3.249 Å) inducing the cationicity of Cu2+and the strength of the interactions clearly decreases for the Pd2+and Pt2+ions (3.785 and 4.610 Å), indicating their electron-rich and nucleophilic characteristics.
  • Tetsuro Kubo, Hideki Tou, Ryoma Miyake, Haruki Matsuno, Hisashi Kotegawa, Hisatomo Harima, Ryuji Higashinaka, Akihiro Nakama, Yuji Aoki, Hideyuki Sato, Yoshihiko Ihara, Takayuki Goto, Michihiro Hirata, Takahiko Sasaki
    Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019), 74(1) ROMBUNNO.14aS‐PS‐74, Mar 18, 2020  Peer-reviewed
  • Suci Winarsih, Faisal Budiman, Hirofumi Tanaka, Tadashi Adachi, Takayuki Goto, Bambang Soegijono, Budhy Kurniawan, Isao Watanabe
    Materials Science Forum, 966 357-362, Aug 1, 2019  Peer-reviewed
    Nano-size effect on structure of crystal of free-standing La2-xSrxCuO4 (LSCO) nanoparticles was observed to reveal size effects of La-based high-Tc superconducting oxides. Lattice parameters were estimated by changing temperature and time of sintering. It is concluded that heat treatment plays a key role in controlling particle size of sample. Lattice distortions will occur when the particle size of sample becomes smaller.
  • T. Goto, Y. Kitamoto, K. Matsui, H. Kuroe, A. Endo, T. Hashimoto, T. Hayashita, S. Iguchi, T. Sasaki
    IEEE TRANSACTIONS ON MAGNETICS, 13(2) 4pages, Dec 7, 2018  Peer-reviewed
    Low-Temperature magnetic properties were investigated on the gold nano particles (GNPs) with an average size of 11.5 nm, assembled with molecules of ruthenium complex (Ru0), and phenylboronic acid (B0) by the proton nuclear magnetic resonance (1H-NMR) and susceptibility measurements. The temperature dependence of the NMR shift and the uniform susceptibility was described as the sum of the Curie-Weiss term and a positive constant term. From the former, the average number of Ru0 on each GNP was estimated to be 118, which is 23% of the calculation. The finite positive constant term shows a clear contrast with the well-known fact that the bulk gold is diamagnetic. Finally, a disappearance of the motional narrowing effect in the proton NMR spectra below 60 K indicates that the wavering motion of Ru0 complexes on GNP at room temperature is frozen at low temperatures.
  • K. Matsui, T. Goto, H. Manaka, Y. Miura
    Journal of Physics: Conference Series, 969(1) 012108-5 pages, Apr 19, 2018  Peer-reviewed
    We have investigated the hyperfine coupling between Cs and Cr on the S = 3/2 equilateral triangular spin tube CsCrF4, utilizing 133Cs-NMR. At paramagnetic state above 80 K, we have obtained spectra containing a single peak, which reflects the single crystallographic Cs site. From the temperature dependence of the peak shift and peak width, we evaluated effective values of the isotropic and the anisotropic part of hyperfine coupling. The latter was compared with the calculated dipole contribution. Using obtained parameters with assumed spin structure, we tried to reproduce the broadened spectrum in the ordered state at 2.0 K. The preliminary analysis shows the 120-degree structure does not accord with the observed spectra at the ordered state.
  • A. Yagi, K. Matsui, T. Goto, M. Hase, T. Sasaki
    Journal of Physics: Conference Series, 969(1), Apr, 2018  Peer-reviewed
    © Published under licence by IOP Publishing Ltd. S = 1/2 competing spin chain compound Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest neighbouring ferromagnetic J 1 = 93 K and the second nearest neighbouring antiferromagnetic J 2 = +33 K, and is expected to show the nematic Tomonaga-Luttinger liquid (TLL) state under high magnetic field region. The recent theoretical study by Sato et al. has shown that in the nematic TLL state, the spin fluctuations are expected to be highly anisotropic, that is, its transverse component is suppressed. Our previous NMR study on the present system showed that the dominant contribution to nuclear spin relaxation comes from the longitudinal component. In order to conclude that the transverse component of spin fluctuations is suppressed, the knowledge of hyperfine coupling is indispensable. This article is solely devoted to investigate the hyperfine coupling of 133Cs-NMR site to prove that the anisotropic part of hyperfine coupling, which connects the nuclear spin relaxation with the transverse spin fluctuations is considerably large to be A an = +770 Oe/μB.
  • Kazuki Matsui, Takayuki Goto, Julia Angel, Isao Watanabe, Takahiko Sasaki, Masashi Hase
    JPS Conf. proc., 21 011008-5 pages, 2018  Peer-reviewed
  • M. Watanabe, N. Kurita, H. Tanaka, W. Ueno, K. Matsui, T. Goto
    Phys. Rev. B, B98(5) 054422-(1-6), 2018  Peer-reviewed
    The double-perovskite compounds Sr2CuTeO6 and Sr2CuWO6 are magnetically described as quasi-two-dimensional spin-12 square-lattice J1-J2 Heisenberg antiferromagnets with predominant J1 and J2 exchange interactions, respectively. We report the low-temperature magnetic properties of Sr2CuTe1-xWxO6 with randomness in the magnitudes of J1 and J2. It was found that the low-temperature specific heat for 0.1≤x≤0.5 has a large component proportional to the temperature T above 1.2 K, although the low-temperature specific heat for the two parent systems is approximately proportional to T3. With decreasing temperature below 1.2 K, the T-linear component decreases rapidly toward zero, which is insensitive to the magnetic field up to 9 T. This is suggestive of the singlet excitation decoupled from the magnetic field. The NMR spectrum for x=0.2 exhibits no long-range order down to 1.8 K. These results indicate that the ground state of Sr2CuTe1-xWxO6 is a valence-bond-glass state with singlet gaps.
  • Kazuki Matsui, Ayato Yagi, Yukihiro Hoshino, Sochiro Atarashi, Masashi Hase, Takahiko Sasaki, Takayuki Goto
    Physical Review B, in press(22), Nov 27, 2017  Peer-reviewed
    A Rb-NMR study has been performed on the quasi-one-dimensional competing spin chain Rb2Cu2Mo3O12 with ferromagnetic and antiferromagnetic exchange interactions on nearest-neighboring and next-nearest neighboring spins, respectively. The system changes from a gapped ground state at zero field to a gapless state at HC≃2T, where the existence of magnetic order below 1 K was demonstrated by a broadening of the NMR spectrum, associated with a critical divergence of 1/T1. In the higher-temperature region, T1-1 showed a power-law-type temperature dependence, from which the field dependence of the Luttinger parameter K was obtained and compared with theoretical calculations based on the spin nematic Tomonaga-Luttinger liquid (TLL) state.
  • M. Yoshida, K. Nawa, H. Ishikawa, M. Takigawa, M. Jeong, S. Kramer, M. Horvatic, C. Berthier, K. Matsui, T. Goto, S. Kimura, T. Sasaki, J. Yamaura, H. Yoshida, Y. Okamoto, Z. Hiroi
    PHYSICAL REVIEW B, 96(18) 180413(R)-(5pages), Nov, 2017  Peer-reviewed
    We report single-crystal V-51 NMR studies on volborthite Cu3V2O7(OH)(2) center dot 2H(2)O, which is regarded as a quasi-two-dimensional frustrated magnet with competing ferromagnetic and antiferromagnetic interactions. In the 1/3 magnetization plateau above 28 T, the nuclear spin-lattice relaxation rate 1/T-1 indicates an excitation gap with a large effective g factor in the range of 4.6-5.9, pointing to magnon bound states. Below 26 T where the gap has closed, the NMR spectra indicate small internal fields with a Gaussian-like distribution, whereas 1/T-1 shows a power-law-like temperature dependence in the paramagnetic state, which resembles a slowing down of spin fluctuations associated with magnetic order. We discuss the possibility of an exotic spin state caused by the condensation of magnon bound states below the magnetization plateau.
  • K. Matsui, M. Fujisawa, H. Tanaka, R. Scheuermann, T. Goto
    Journal of Physics: Conference Series, 828(1) 012011-012016, Apr 20, 2017  Peer-reviewed
    We have investigated high-field TF-μ SR and 1H-NMR on the S = 1/2 three dimensional spin dimer system NH4CuCl3, which shows a magnetic order at TN = 1.29 K under zero field and the two-stepped plateaus in high field regions HC1 = 5.0 T - HC2 = 12.8 T and HC3 = 17.9 T - HC4 = 24.7 T. Both probes showed spectra containing multiple peaks corresponding to different hyperfine fields, demonstrating the existence of magnetically inequivalent dimers in a unit cell. In the slope-state field region H &lt HC1, the existence of magnetic order was confirmed by the splitting in some of the NMR peaks. The whole width of NMR and μ SR spectra increased with increasing field, and no drastic change in their profile was observed at HC1. This indicates that the change in the spin state is continuous on entering the plateau state, and that no liquid-solid transition of magnons takes place at the phase boundary.
  • R. Uesugi, M. Akaki, M. Hagiwara, H. Kuwahara, T. Goto
    Journal of Physics: Conference Series, 828(1) 012015-012018, Apr 20, 2017  Peer-reviewed
    NMR study has been performed on the quasi-one dimensional antiferromagnet BaCo2Si2O7, in which three inequivalent CoO4 tetrahedra, slightly tilted from one another, are linked at vertices to form a chain along the easy-axis c. In its magnetically ordered state at 3.6 K, 59Co-NMR spectra were measured in the field region up to 12 T. From the observed three distinct sets of quadrupolar-split peak groups, three different hyperfine fields at Co sites were determined. They are slightly tilted from c-axis and are all different both in magnitude and direction, which is in agreement with the non-collinear magnetic structure.
  • T. Goto, A. Yagi, K. Matsui, I. Watanabe, T. Sasaki, M. Hase
    Journal of Physics: Conference Series, 828(1) 012017-012021, Apr, 2017  Peer-reviewed
    © Published under licence by IOP Publishing Ltd. S = 1/2 quasi one dimensional Heisenberg chain Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest-neig hbouring ferromagnetic J1 = -93 K and the second nearest-neighbouring antiferromagnetic J2 = +33 K. These competing interactions on the spin chain are expected to bring rich physics, such as frustration or nematic Tomonaga-Luttinger liquid (TL) phase. In order to investigate its ground state at zero and finite fields, we have performed 133Cs-NMR experiments under the wide range of magnetic field up to 14 T, and μ-SR at zero field. In low-field region, the existence of long range magnetic order was demonstrated below 2 K. In the higher field region between 7 T and the saturation field Hs = 9.15 T, no evidence for magnetic order was confirmed at finite temperatures.
  • A. Yagi, K. Matsui, T. Goto, M. Hase, T. Sasaki
    Journal of Physics: Conference Series, 828(1) 012016-012020, Apr, 2017  Peer-reviewed
    © Published under licence by IOP Publishing Ltd. Quasi-one-dimensional S = 1/2 Heisenberg system Rb2Cu2Mo3O12 described by the J1 - J2 model with the nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic exchange interactions have been investigated by 87/85Rb-NMR under extended field range up to 18 T. From the thermal-activation-type temperature dependence of l/T1, opening of the spin excitation gap was confirmed under the low field below 2 T. With increasing the field, the system becomes gapless, and the gap opens again in the high field saturation region, where the field dependence of the gap size showed the coherent excitation of the neighbouring two spins.
  • Matsui K., Goto T., Manaka H., Miura Y.
    Meeting Abstracts of the Physical Society of Japan, 72 1213-1213, 2017  
  • S. Kobori, K. Matsui, H. Kuwahara, T. Goto, X. Zhang, Y. Nakano, S. Nishihara, K. Inoue, T. Sasaki
    Hyperfine Interactions, 237(1) 116 (page 1 of 7)-116 (page 7 of 7), Aug 10, 2016  Peer-reviewed
  • Y. Ihara, Y. Futami, A. Kawamoto, K. Matsui, T. Goto, T. Sasaki, S. Benmansour, C. J. Gomez-Garcia
    PHYSICAL REVIEW B, 94(6) 064504-064509, Aug, 2016  Peer-reviewed
    We present the results of C-13 NMR experiments in an organic superconductor with localized Fe spins beta ''-(BEDT-TTF)(4)[(H3O)Fe(C2O4)(3)] center dot C6H5Br. We reveal the antiferromagnetic coupling between Fe d spins and pi spins, which creates an exchange field antiparallel to the external field direction at the pi electrons. In addition to the static effects of Fe spins, we show from the nuclear spin-lattice relaxation rate measurement that the magnetic fluctuations generated by Fe spins are suppressed at low temperatures and high magnetic fields. These conditions are suitable to stabilize the field-induced superconductivity by the field compensation mechanism. After the suppression of Fe-spin dynamics by a magnetic field of 19 T, we observed the underlying pi-electron contribution. We discuss a possible anomaly in the pi-electron system.
  • Shohei Kobori, Kazuki Matsui, Hideki Kuwahara, Takayuki Goto, Xiao Zhang, Yuki Nakano, Sadafumi Nishihara, Katsuya Inoue, Takahiko Sasaki
    HYPERFINE INTERACTIONS, 237(1) 116-122, Aug, 2016  Peer-reviewed
    The two-legged spin ladder Cu(CO3)(0.5)(ClO4)(H2O)(0.5)(NH3)(2.5) consists of a rung formed by two Cu(II)'s and of a spacing molecule CO32- between each two rungs. The non-centrosymmetric shape of CO32- molecule brings a slight bond alternation along the leg, and hence the system can be considered as an alternating spin chain, which is confirmed so far by the temperature dependence of magnetic susceptibility. In order to investigate its spin state at low temperatures, we have performed experiments of H-1-NMR, magnetization and specific heat under wide range of magnetic field, and have found the critical diverging of longitudinal relaxation rate 1/T-1, the spectral broadening and the lambda-type anomaly in specific heat at T-N similar or equal to 3.4 K, indicating the existence of long range magnetic order. In paramagnetic state well above T-N, 1/T-1 showed a power-law temperature dependence, suggesting the realization of Tomonaga Luttinger liquid state.
  • Kazuki Matsui, Takayuki Goto, Hirotaka Manaka, Yoko Miura
    HYPERFINE INTERACTIONS, 237(1) 123-128, Aug, 2016  Peer-reviewed
    The ground state of the frustrated equilateral triangular spin tube CsCrF4 is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by F-19-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120 degrees-type structure in ab-plane does not accord with the NMR spectra of ordered state.
  • Hosoya Y., Goto T., Endo A., Hashimoto T., Hayashita T., Iguchi S., Sasaki T.
    Meeting Abstracts of the Physical Society of Japan, 71 1067-1067, 2016  
  • Uesugi R., Akaki M., Hagiwara M., Kuwahara H., Goto T.
    Meeting Abstracts of the Physical Society of Japan, 71 1033-1033, 2016  
  • Matsui K., Goto T., Manaka H., Miura Y.
    Meeting Abstracts of the Physical Society of Japan, 71 1082-1082, 2016  
  • Yagi Ayato, Matsui Kazuki, Hoshino Yukihiro, Hosoya Yousuke, Goto Takayuki, Hase Masashi, Sasaki Takahiko
    Meeting Abstracts of the Physical Society of Japan, 71 958-958, 2016  
  • Goto Takayuki, Matsui Kazuki, Hosoya Yosuke, Hashimoto Takeshi, Endo Akira, Hayashita Takashi, Iguchi Satsoshi, Sasaki Takahiko
    Meeting Abstracts of the Physical Society of Japan, 71 1569-1569, 2016  
  • Kubo Tetsuro, Miyake Ryoma, Matsuno Haruki, Kotegawa Hisashi, Tou Hideki, Harima Hisatomo, Higashinaka Ryuji, Nakama Akihiro, Aoki Yuji, Sato Hideyuki, Ihara Yoshihiko, Goto Takayuki, Sasaki Takahiko
    Meeting Abstracts of the Physical Society of Japan, 71 2108-2108, 2016  
  • Takamatsu Y., Fujiwara K., Suwada Y., Motoyama G., Miyoshi K., Kobayashi T. C., Kitagawa K., Sasaki T., Goto T., Seiro S., Geibel C., Steglich F.
    Meeting Abstracts of the Physical Society of Japan, 71 2008-2008, 2016  
  • Uesugi R., Akaki M., Hagiwara M., Kuwahara H., Goto T.
    Meeting Abstracts of the Physical Society of Japan, 71 1003-1003, 2016  
  • Matsui K., Guo H., Watanabe I., Suzuki T., Fujisawa M., Tanaka H., Scheuermann R., Goto T.
    Meeting Abstracts of the Physical Society of Japan, 71 733-733, 2016  
  • Kawase T., Goto T., Kuroe H., Sekine T., Sasaki T., Hase M., Oka K., Ito T., Eisaki H.
    Meeting Abstracts of the Physical Society of Japan, 71 1048-1048, 2016  
  • Kazuki Matsui, Takayuki Goto, Hirotaka Manaka, Yoko Miura
    Physics Procedia, 75 726-730, Dec 29, 2015  Peer-reviewed
    In order to investigate the hyperfine coupling of three inequivalent 19F sites in the equilateral triangular spin-tube antiferromagnet CsCrF4, we have measured the temperature dependence of 19F-NMR Knight shift in the paramagnetic state above 20K. The hyperfine coupling constants for three F-sites were determined to be -0.170, 0.280 and -0.045 T/μB, and were found to be consistent with the observed spectra at 1.65K, where the system is possibly in the ordered state.
  • Suwada Y., Fujiwara K., Motoyama G., Miyoshi K., Kobayashi T. C., Sasaki T., Goto T., Seiro S., Geibel C., Steglich F.
    Meeting Abstracts of the Physical Society of Japan, 70 1813-1813, 2015  
  • Matsui K., H. Guo, Watanabe I., Suzuki T., Fujisawa M., Tanaka H., Goto T.
    Meeting Abstracts of the Physical Society of Japan, 70 757-757, 2015  
  • Hosoya Y., Goto T., Endo A., Hashimoto T., Hayashita T., Iguchi S., Sasaki T.
    Meeting Abstracts of the Physical Society of Japan, 70 759-759, 2015  
  • Yagi Ayato, Matsui Kazuki, Hoshino Yukihiro, Hosoya Yousuke, Goto Takayuki, Hase Masashi, Sasaki Takahiko
    Meeting Abstracts of the Physical Society of Japan, 70 745-745, 2015  
  • Hosoya Y., Goto T., Tanaka H.
    Meeting Abstracts of the Physical Society of Japan, 70 1033-1033, 2015  
  • Kawase T., Misoka K., Hamasaki T., Kuroe H., Goto T., Sekine T., Sasaki T., Hase M., Oka K., Ito T., Eisaki H.
    Meeting Abstracts of the Physical Society of Japan, 70 970-970, 2015  
  • Yoshida M., Nawa K., Takigawa M., Jeong M., Kramer S., Horvatic M., Berthier C., Matsui K., Goto T., Kimura S., Sasaki T., Ishikawa H., Yamaura J., Yoshida H., Okamoto Y., Hiroi Z.
    Meeting Abstracts of the Physical Society of Japan, 70 1237-1237, 2015  
  • Kawase T., Goto T., Kuroe H., Sekine T., Sasaki T., Hase M., Oka K., Ito T., Eisaki H.
    Meeting Abstracts of the Physical Society of Japan, 70 806-806, 2015  
  • Matsui K., Hoshino Y., Hosoya Y., Goto T., Hase M., Sasaki T.
    Meeting Abstracts of the Physical Society of Japan, 70 1121-1121, 2015  
  • Takayuki Goto, Kazuki Matsui, Tadashi Adachi, Tomi Ohtsuki, Ngoc Han Tu, Yoichi Tanabe, Katsumi Tanigaki, Isao Watanabe, Zaher Salman, Andreas Suter, Thomas Prokscha
    20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015, 75 100-105, 2015  Peer-reviewed
    A new method utilizing the low energy muon spin rotation (mu SR) technique to investigate the spin structure within the surface layer of topological insulator has been proposed. In order to detect the spin polarization parallel with the surface, one applies a weak field B-par, which, by breaking the time reversal symmetry, is expected to induce a net magnetization perpendicular the surface. This will affect the profile of muon spin depolarization spectra. Preliminary measurements on the topological insulator Bi1.5Sb0.5TeSe2 with tetradymite structure are also shown.
  • Yosuke Hosoya, Takayuki Goto, Akira Endo, Takeshi Hashimoto, Takashi Hayashita, Satoshi Iguchi, Takahiko Sasaki
    20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015, 75 613-617, 2015  Peer-reviewed
    Substituting effect of CF3 to the Ru-based binuclear complex [{Ru-III( acac)(2)}(2)(mu-OEt)(2)], in which S = 1/2 spin dimer takes the singlet ground state have been investigated by means of the magnetic susceptibility chi and the longitudinal nuclear spin relaxation rate T-1(-1) of H-1/F-19-NMR. In CF3-substituted complex [{Ru-III(fhma)(2)}(2)(chi-OMe)(2)], we have observed the prominent magnetic response both in chi and T-1(-1). This behavior is attributed to the slight change in the Ru valence state due to the substitution.
  • T. Kawase, T. Goto, H. Kuroe, T. Sekine, T. Sasaki, M. Hase, K. Oka, T. Ito, H. Eisaki
    20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015, 75 641-646, 2015  Peer-reviewed
    Quasi one dimensional antiferromagnet Cu3Mo2O9 consists of spin chains and inequivalent spin pairs clinging on them, and shows the magnetic order at T-N = 7.9 K. The local structure of tetrahedron formed by neighboring four spins suggests a non-collinear spin structure in the ordered state and hence the multiferroicity. We have performed Cu-NMR measurements at low temperatures below T-N and showed that the observed spectra are consistent with the report by the recent neutron elastic scattering experiments in that the chain site Cu has only an extremely small ordered moment.
  • Takao Suzuki, Hanjie Guo, Ikuto Kawasaki, Isao Watanabe, Takayuki Goto, Kazuya Katayama, Hidekazu Tanaka
    Journal of the Physical Society of Japan, 83(8) 084703.1-084703.5, Aug 15, 2014  Peer-reviewed
    Longitudinal-field muon spin-relaxation (LF-μSR) measurements have been performed in a bond-randomness introduced quantum spin system, Tl1-xKx CuCl3 with x = 0.40, in which the appearance of a Bose glass (BG) phase adjacent to the Bose-Einstein condensation (BEC) phase of excited triplets is observed. In the zero- field limit below 500 G, LF-μSR time spectra shows an exponential-like decay, and the muon spin-relaxation rate does not have a significant temperature dependence down to 25 mK. This indicates that spins fluctuate in time and in space, and that the spin system is not into a spin gapped state. It is suggested that the theoretically predicted gapped Mott insulating phase adjacent to the BG phase disappears in this case. This result obtained by microprobe LF-μSR measurements is consistent with an indication deduced from the results of macroscopic magnetization measurements.
  • Takao Suzuki, Hanjie Guo, Ikuto Kawasaki, Isao Watanabe, Takayuki Goto, Kazuya Katayama, Hidekazu Tanaka
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 83(8), Aug, 2014  Peer-reviewed
    Longitudinal-field muon spin-relaxation (LF-mu SR) measurements have been performed in a bond-randomness introduced quantum spin system, Tl1-xKxCuCl3 with x = 0.40, in which the appearance of a Bose glass (BG) phase adjacent to the Bose-Einstein condensation (BEC) phase of excited triplets is observed. In the zero-field limit below 500 G, LF-mu SR time spectra shows an exponential-like decay, and the muon spin-relaxation rate does not have a significant temperature dependence down to 25 mK. This indicates that spins fluctuate in time and in space, and that the spin system is not into a spin gapped state. It is suggested that the theoretically predicted gapped Mott insulating phase adjacent to the BG phase disappears in this case. This result obtained by microprobe LF-mu SR measurements is consistent with an indication deduced from the results of macroscopic magnetization measurements.
  • Kazuki Matsui, Masashi Fujisawa, Kenta Hagiwara, Yukihiro Hoshino, Takayuki Goto, Takahiko Sasaki, Hidekazu Tanaka, Susumu Okubo, Hitoshi Ohta
    JPS Conference Proceedings, 3 014011, Jun, 2014  Peer-reviewed
  • Yukihiro HOSHINO, Soichiro ATARASHI, Takayuki GOTO, Masashi HASE, Takahiko SASAKI
    JPS Conference Proceedings, 3 014012, Jun, 2014  Peer-reviewed

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