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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
  • S Endo, T Goto, H Uozaki, T Fukase, K Ueda, T Sugimoto, N Toyota
    PHYSICA B, 281(1-3) 682-683, Jun, 2000  
    We report on H-1-NMR measurements of an organic pi-d metal kappa-(BEDT-TSF)(2)FeCl4, where BEDT-TSF is bis(ethylenedithio)tetraselenafulvalene. C10S4Se4H8. The protons exclusively located at the terminal ethylene are expected to be sensitive to the internal magnetic fields produced by Fe3+ 3d-spins. At high temperatures. the single sharp peak is observed in spectra. Very wide tails are observed at both sides of the central peak below 4 K, where spin-lattice relaxation rate T-1(-1) shows the fast and slow components corresponding to the wide tails and central sharp peak. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Tetsuo Fukase, Tomoyuki Shinoda, Yuichi Oshima, Takao Suzuki, Kaichiro Chiba, Takayuki Goto, Kazuyoshi Yamada
    Physica B: Condensed Matter, 284-288(I) 483-484, 2000  
    Temperature dependence of the velocity Vs and the attenuation of the ultrasonic waves are measured to investigate the relation between the spin type of magnetic order and lattice instability of the low-temperature tetragonal phase in La2-xSrxCuO4 (x ∼ 1/8). In the field above 8 T along the [0 1 0]o direction of the orthorhombic notation, a significant increase of Vs in the c44 mode is observed below ∼15 K where spin-flop occurs. This gigantic increase of Vs suggests that the structural transformation from the orthorhombic to the low-temperature tetragonal phase is induced by the spin-flop. © 2000 Elsevier Science B.V. All rights reserved.
  • T Goto, S Nakajima, E Ohshima, M Kikuchi, Y Syono, T Fukase
    JOURNAL OF LOW TEMPERATURE PHYSICS, 117(3-4) 467-471, Nov, 1999  
    The Spin-lattice relaxation rate T-1(-1) and the Knight shift have been measured for Tl-based cuprates TlBa2CaCu2O7+delta (TB1212) and TlSr2Y1-xCaxCu2O7+delta (TS1212). In the underdoped sample of TS1212 with T-C=34K, (T1T)(-1) showed a gap-like behavior from the temperature T-SG=120K. As for the slightly overdoped sample of TB1212 with T-C=80K, both the Knight shift and (T1T)(-1) showed a significant decrease from 160K, suggesting the existing of the spin-gap not only around q similar or equal to(pi,pi), but also q similar or equal to 0.
  • K Chiba, T Goto, M Mori, T Suzuki, K Seki, T Fukase
    JOURNAL OF LOW TEMPERATURE PHYSICS, 117(3-4) 479-483, Nov, 1999  
    The external field dependence of the hyperfine field at La-site has been studied on La2-xSrxCuO4 (x=0.115) anal La2-xBaxCuO4 (x=0.125), where the magnetic ordering in Cu-3d spins exists at low temperature. In La1.885Sr0.115CuO4, a significant decrease in the resonance line width was observed above a field of H-c approximate to 7.5T, which is the direct evidence of the spin-flop in the canted-spin system with Dzyaloshinski-Moriya interaction. The spin-flop field H-c of 7.5T is slightly lower than that in La2CuO4 (H-c approximate to 10T), reflecting the decrease of the tilting angle of the CuO6 octahedra by the substitution of Sr2+ ion for La-site.
  • T Fukase, H Geka, T Goto, K Chiba, T Suzuki
    JOURNAL OF LOW TEMPERATURE PHYSICS, 117(3-4) 491-495, Nov, 1999  
    La-NMR, Hall coefficient and sound velocity have been measured in order to investigate the correlation between the magnetic ordering, the prominent change of transport properties, the suppression of T-c and the structural transformation around x similar to 1/8 in La1.96-xY0.04SrxCuO4. By the substitution of 0.04/2 Y for La-sites, the structural transformation to the low temperature tetragonal phase (LTT) is caused at 57+/-14 K for samples around x similar to 0.115. The prominent decrease of the Hall coefficient followed by the sign reversal and the magnetic ordering are observed around x similar to 0.115 below temperatures T-s and T-N, respectively. T-s vs x shows a bell shaped curve with the maximum value of 65 K at x similar to 0.115 where most prominent suppression of T-c appears. T-N shows similar x dependence to T-s with the maximum value of 40 K at x similar to 0.115. The change of the electronic state below T-s and the suppression of T-c become more prominent and the magnetic ordering is observed more wide range of a: under the LTT phase.
  • T Suzuki, Y Oshima, K Chiba, T Fukase, GOTO TAKAYUKI, H Kimura, K Yamada
    Physical Review B, 60(14) 10500-10503, Oct, 1999  
  • C. ギロー, 他著, 後藤貴行
    パリティ, 14(10), Oct, 1999  
    翻訳「NMRでインチキワインを嗅ぎ分ける」 http://pub.maruzen.co.jp/book_magazine/magazine/parity-back/parity1999/1999_10/910_cont.html http://pub.maruzen.co.jp/book_magazine/magazine/parity-back/parity1999/1999_10/910_person.html
  • S Endo, Y Watanabe, H Uozaki, K Okamoto, M Yamaguchi, T Goto, T Fukase, N Toyota
    SYNTHETIC METALS, 103(1-3) 2075-2075, Jun, 1999  
    We have measured the temperature dependence of lattice parameters of the title salts from 300 down to 11 K by a four circle Xray diffractometer. It is confirmed that the ND4Hg(SCN)(4) salt shows essentially the same anisotropic contraction of the cia with the NH4Hg(SCN)(4) salt. The deuteration enhances the cia ratio by 0.3 % at low temperatures.
  • S Endo, T Goto, T Fukase, H Uozaki, K Okamoto, M Yamaguchi, N Toyota
    SYNTHETIC METALS, 103(1-3) 2073-2074, Jun, 1999  
    We have measured the temperature dependence of the spectrum and the spin-lattice relaxation time T-1, by D-2 nuclear-magnetic-resonance (NMR) for alpha-(h(8)-ET)(2)ND4Hg(SCN)(4) and H-1-NMR for alpha-(d(8)-ET)(2)NH4Hg(SCN)(4) in order to clarify the molecular dynamics of the non-centrosymmetric ND4+ and NH4+ ions. Both the systems show the peak in T-1(-1) around 40 K explained by Bloembergen-Purcell-Pound model, while the temperature dependence of the spectra were quite different.
  • Y Furukawa, Okamura, I, K Kumagai, T Goto, T Fukase, Y Taguchi, Y Tokura
    PHYSICAL REVIEW B, 59(16) 10550-10558, Apr, 1999  Peer-reviewed
    Carrier-doping effects on electronic correlations on the verge of the Mott transition in La1-xSrxTiO3 have been investigated by Ti-47/49 and La-139 NMR. In antiferromagnetic (AF) insulator of LaTiO3 with TN = 140 K, we observed zero-field Ti NMR and determine the hyperfine field of 91.4 kOe for Ti nuclei. The increases of nuclear spin-lattice relaxation rates (T-1)(-1) of La and Ti show that effective carrier mass is enhanced critically as the Mott transition boundary is approached from the metallic side. We have no evidence for a prominent increase of AF spin fluctuations at q similar to Q near the Mott transition boundary. Together with the temperature dependence of T-1 (The Korringa relations of T1T=const are observed for La and Ti) in the metallic state, we conclude that the AF spin fluctuations of Ti-3d spins due to the interatomic electronic correlations is not important, but single-site (intraband) electronic correlations play an important role in driving the metal-insulator transition in La1-xSrxTiO3, as opposed to the case of high-T-c cuprates. [S0163-1829(99)13415-5].
  • Y Furukawa, I Okamura, K Kumagai, GOTO TAKAYUKI, T Fukase, Y Taguchi, Y Tokura
    Physical Review B, 59(16) 10550-10558, Apr, 1999  
  • T. Suzuki, Y. Oshima, K. Chiba, T. Fukase, T. Goto, H. Kimura, K. Yamada
    Physical Review B - Condensed Matter and Materials Physics, 60(14) 10500-10503, 1999  
    The superconducting transition in the electrical resistivity has been examined for La2-xSrxCuO4 (x ∼ 0.12) single crystals in magnetic fields. The broadening of the transition width in high fields is small compared to the case of the optimum doping (x ∼ 0.15) and the transition curve as a function of the temperature in each magnetic field shifts to lower temperature in almost parallel with applying magnetic field similar to the case of conventional superconductors. These results indicate that the superconducting fluctuation is weakened and that the coherence length in the CuO2plane becomes much longer around x=0.12. The measurement results are discussed in relation to the appearance of long-range magnetic order. © 1999 The American Physical Society.
  • Masahide Yokoi, Tohru Okamoto, Shinji Kawaji, Takayuki Goto, Tetsuro Fukase
    Physica B: Condensed Matter, 249-251 93-96, Jun 17, 1998  
    Breakdown of non-conductive state of Corbino discs at integer filling factors of Landau levels at high source-drain voltages has been measured for samples fabricated from GaAs/Al0.3Ga0.7As heterostructures. Critical breakdown electric fields at the filling factors of 1, 2, 4 and 6 are in agreement with the critical breakdown Hall electric fields in the quantized Hall plateaus with these quantum numbers measured in butterfly-type Hall bars. © 1998 Elsevier Science B.V. All rights reserved.
  • Endo, S., Goto, T., Fukase, T., Uozaki, H., Okamoto, K., Toyota, N.
    Physical Review B, 57(22) 14422-14427, Jun, 1998  
  • T Goto, T Suzuki, K Chiba, T Shinoda, M Mori, T Fukase
    PHYSICA B, 246 572-575, May, 1998  
    The effect of the magnetic field on the crystal structural and the magnetic ordering at low temperatures of La2-xSrxCuO4 (x similar to 1/8) has been studied using the ultrasonic and NMR measurements. An increase of the sound velocity V-s below T-d2(u) (similar to 10 K at H = 0) is drastically enhanced by applying the field, suggesting that the magnetic field promotes the structural phase transition to the tetragonal phase. A broadening of the resonance line of La-NMR in the magnetically ordered state below T-N (similar to 35 K at x = 0.115)shows a significant shrink by applying a high magnetic field of 15 T, which is interpreted as the spin-flop in the canted-spin system with the Dzyaloshinski-Moriya interaction. A model is proposed to explain both this spin-flop and the field-dependent structural instability described above in this system. (C) 1998 Elsevier Science B.V. All rights reserved.
  • T Suzuki, GOTO TAKAYUKI, K Chiba, T Shinoda, T Fukase, H Kimura, K Yamada, M Ohashi, Y Yamaguchi
    Physical review. B, Condensed matter, 57(6) 3229-3232, Feb, 1998  
  • T. Suzuki, T. Goto, K. Chiba, T. Shinoda, T. Fukase, H. Kimura, K. Yamada
    Physical Review B - Condensed Matter and Materials Physics, 57(6) R3229-R3232, 1998  
    Magnetic superlattice peaks are observed in single-crystal neutron-diffraction measurements on orthorhombic (Formula presented) at reciprocal points of (1/2±ε,1/2,0) and (1/2,1/2±ε,0) in the tetragonal notation where (Formula presented)0.126(Formula presented)0.003. The La NMR measurement reveals a broadening of the field-swept spectrum below (Formula presented)45 K corresponding to the existence of magnetic order. The remarkable softening of longitudinal sound waves along [110] is observed in the same crystal. The features observed in the neutron diffraction, NMR, and ultrasonic measurements suggest that the dynamical incommensurate spin correlation is pinned by a lattice instability toward the low-temperature tetragonal phase. © 1998 The American Physical Society.
  • NMR
    S. Endo, T. Goto, T. Fukase, H. Uozaki, K. Okamoto, N. Toyota
    Physical Review B - Condensed Matter and Materials Physics, 57(22) 14422-14427, 1998  
    We report (Formula presented) measurements on a single crystal of superconducting (Formula presented) where (Formula presented) is bis(ethylenedithiotetrathiafulvalene), (Formula presented) The temperature dependence of the spectrum has revealed that two phase transitions occur on cooling; first at (Formula presented) where a single resonance peak splits into two subpeaks, and second at (Formula presented) where the subpeaks disappear after the broadening at 25 K. The former associated by temperature hysterisis is a first-order phase transition and the splitting width follows (Formula presented) dependence. This splitting, which is so sensitive to the field orientation due to (Formula presented) is found to be caused by the quadrupole interaction. The spin-lattice relaxation rate (Formula presented) is strongly elongated by three orders of magnitude with decreasing temperature from 200 K, followed by the maximum around 40 K. This dramatic effect is interpreted by the Bloembergen-Purcell-Pound model applied to the quadrupole interaction. Discussions are made from the viewpoint of the dynamics of noncentrosymmetric tetrahedral molecule (Formula presented) at (Formula presented) the uniform rotation might switch to the thermally activated hopping motion between preferable sites bonded to nitrogens of (Formula presented) legands and then the order-disorder transition might eventually occur at (Formula presented) to form an anion ordering. © 1998 The American Physical Society.
  • T Goto, K Chiba, M Mori, T Suzuki, K Seki, T Fukase
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 66(9) 2870-2874, Sep, 1997  
    The effect of the external field on La-NMR spectra has been studied on La-based high-T-c cuprates La2-xSrxCuO4 (x approximate to 0.115) and La2-xBaxCuO4 (x = 0.125), where the magnetic ordering in Cu-3d spin exists at low temperature. In the magnetically ordered state, the broadening in the resonance line was observed, reflecting the hyperfine field at the La-site contributed by the Cu-3d spins. By applying a high magnetic field of 15 T, this broadening in La2-xSrxCuO4 showed a significant shrink, which is interpreted as the spin-flop in the canted-spin system with the Dzyaloshinski-Moriya interaction. A model is proposed to explain both this spin-flop and the previously-reported anomalous field dependence of the structural instability in this system.
  • Y Furukawa, Okamura, I, K Kumagai, T Goto, T Fukase, Y Taguchi, Y Tokura
    PHYSICA C, 282 1103-1104, Aug, 1997  
    Carrier doping effects on electronic correlations in La1-xSrxTiO3 have been investigated by Ti-47/49 and La-139 NMR The increases of nuclear spin-lattice relaxation rates, (T1T)(-1), of both La and Ti provide the critical enhancements of effective carrier mass on approaching the Mott transition phase boundary from the metallic side. We have no evidences for a prominent increase of antiferromagnetic spin fluctuations at q similar to Q near the Mott-transition boundary, which is sharply contrast to the case of high-T-c cuprates.
  • T Goto, T Watanabe, K Kinoshita, A Matsuda, M Sera, T Fukase
    JOURNAL OF LOW TEMPERATURE PHYSICS, 105(3-4) 401-406, Nov, 1996  
    Cu-NMR spectra and the nuclear spin-lattice relaxation rate T-1(-1) have been studied intensively on the bilayer type high-T-C cuprate La1.89Ca1.11Cu2O6+delta (La2126). The resonance line shift showed a monotonic decrease with lowering temperature in the normal state, indicating that this compound belongs to the lightly-doped region. The Curie-Weiss temperature dependence of (T1T)(-1) in the normal state shows that the pseudo spin-gap does nor always exist in the light-doped bilayer systems.
  • T Goto, S Nakajima, M Kikuchi, Y Syono, T Fukase
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 65(11) 3666-3671, Nov, 1996  
    Cu-63/65/Tl-203/205-NMR study has been performed on the Zn-substituted high-T-C cuprate TlBa2Ca(Cu1-zZnz)(2)O-7+delta belonging to the over-doped region. The reduction rate in T-C with Zn-concentration was much smaller than the lightly-doped cuprate La1.85Sr0.15CuO4, and showed a significant decrease with increasing hole concentration. The temperature dependence of the Cu-Knight shift in the superconducting state was successfully explained in terms of the partially closed d-wave model proposed by Ishida et al. The relation between the residual density of states in the superconducting state and the reduction rate of T-C with Zn-concentration for slightly over-doped samples was well explained with Miyake's theoretical calculation on the potential scattering of the unitarity limit in the d-wave superconductor.
  • GOTO TAKAYUKI, Watanabe Takao, Kinoshita Kyoichi, 他, MATSUDA Azusa, SERA Masafumi, SAKATSUME Shinichi, FUKASE Tetsuo
    Journal of the Physical Society of Japan, 65(9) 2768-2771, Sep, 1996  
  • T Goto, T Watanabe, K Kinoshita, A Matsuda, M Sera, S Sakatsume, T Fukase
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 65(9) 2768-2771, Sep, 1996  
    The temperature dependence of the Cu-63/65-NMR relaxation rate T-1(-1) and the spectrum of the lightly doped high-T-c cuprate La1.89Ca1.11Cu2O6+delta (La2126) with bilayer CuO planes have been studied. The field-swept spectrum tvas explained by assuming that there are two Cu sites with quadrupole frequencies of (63)nu(Q) = 25.6 and 32 MHz. The Knight shift decreased monotonically with decreasing temperature in the normal state, which is consistent with the reported result that the system belongs to the Lightly doped region where the hole content is less than the optimum value. The Curie-Weiss temperature dependence of (T1T)(-1) = 2600/(T + 110) (K . s)(-1) in the normal state down to T-c indicates that the pseudo-spin gap does not always exist in lightly doped bilayer systems.
  • T Goto, S Nakajima, M Kikuchi, Y Syono, T Fukase
    PHYSICAL REVIEW B, 54(5) 3562-3570, Aug, 1996  
    The end member of the T1-based high-T-c cuprate TIBa2YCu2O7 (Tl1212) with the zero nominal hole number has been synthesized and studied by Cu/Tl NMR. The existence of the antiferromagnetic ordering was demonstrated by the Zeeman-splitted zero-field Cu spectra. Static parameters at the Cu site such as the hyperfine field H-Cu=8.62 T and the quadrupolar frequency (63)v(Q)=20.44 MHz were found to be comparable to other high-T-c related antiferromagnets La2CuO4 and YBa2Cu3O6. The relaxation rate T-l(-1) of the Cu site of Tl1212 showed a significant deviation from the magnon theory, and was much smaller than La2CuO4 and YBa2Cu3O6. The scaling between the temperature dependence of Tl T-l(-1) and Cu T-l(-1), the ratio of which was consistently explained with the hyperfine coupling constants determined by the analysis of spectra, showed that the relaxation is dominated by the 3d spin fluctuation. A possible relation between the spin fluctuation in the antiferromagnetic phase and the superconductivity in the high-T-c phase is also stated.
  • GOTO TAKAYUKI, Seki K, Chiba K, Miyagawa K, Kazama S, Fukunaga M, Nakajima S, Kikuchi M, Syono Y, Fukase T
    Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy, 42(2) 339-349, Jul, 1996  
  • Kawaji S, Fukano A, Okamoto T, GOTO TAKAYUKI, Fukase T
    Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy, 42(2) 259-262, Jul, 1996  
  • Fukase T, Hanaguri T, Kamata M, Ishizuka K, Suzuki T, GOTO TAKAYUKI, Sasaki T
    Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy, 42(2) 327-331, Jul, 1996  
  • Takayuki Goto, Satoru Nakajima, Masae Kikuchi, Yasuhiko Syono, Tetsuo Fukase
    Physica C: Superconductivity and its Applications, 263(1-4) 253-256, May, 1996  
    The non-magnetic impurity effect has been investigated by NMR on Zn-doped TlBa2CaCu2O7 + δ belonging to the over-doped region, where the reduction rate in Tc with Zn-doping was found to be approximately - 2.3 K/%, much smaller than La1.85Sr0.15CuO4 and YBa2Cu3O7. The temperature dependence of the Cu-NMR Knight shift was analyzed with the partially closed d-wave model proposed by Ishida et al. to find that the residual density of states at the Fermi level increases with the Zn-concentration. The ratio between the residual density of states and the reduction rate in Tc was found to be in accordance with the theoretical calculation in the unitarity limit by Miyake.
  • T Goto, K Chiba, M Fukunaga, T Fukase
    PHYSICA C, 263(1-4) 355-358, May, 1996  
    The magnetization of 4f-spins in the electron-doped high-T-c cuprate with T'-type structure M(2-x)Ce(x)CuO(4) (M = Nd, Pr, Sm, Eu) has so far prevented NMR studies of the Cu 3d-spin and the conduction carrier. We have successfully synthesized the 4f-spin-free cuprate (La1-yYy)(2-x)CexCuO4 for Cu-NMR study. The observed sharp spectra of Cu-63/65 without quadrupolar splittings similar to other conventional electron-doped cuprates like Nd2-xCexCuO4 indicate that the doped carrier in this system is electron-like. With Ar-annealing treatment, though the electrical resistance showed a drastic reduction, the Cu-NMR Knight shift did not change appreciably, suggesting that the Ar-annealing treatment does not bring any change in the carrier concentration.
  • K Seki, T Goto, T Fukase
    PHYSICA C, 263(1-4) 290-293, May, 1996  
    La-NMR and ultrasonic studies have been performed on Zn2+-and Ce4+-doped high-T-c cuprate La2-xBaxCuO4 with x around 1/8, where the superconductivity is anomalously suppressed. The investigations of the substituent concentration dependence of the magnetic and the structural phase transition temperatures have revealed that the main and direct force for the suppression of the superconductivity is the magnetic ordering around the hole concentration 1/8, and that the structural phase transformation enhances the suppression.
  • T Fukase, M Kamata, K Ishizuka, T Suzuki, T Goto, T Sasaki
    PHYSICA C, 263(1-4) 420-423, May, 1996  
    The anisotropy of the activation energy of the flux pinning in a La1.85Sr0.15CuO4 single crystal was investigated by ultrasonic measurements in various directions of wave vector k, polarization vector u and magnetic fields H. The large activation energy of U(0 K, 14 T) = 972 K and small field dependence alpha H--0.3 were obtained for H parallel to c-plane, when the flux motion is parallel to the c-axis where the intrinsic pinning mechanism due to the layered structure is effective. The elastic modulus of the flux-line lattice which moves parallel to the c-axis is proportional to H-2 cos (2) theta, and the value of U rapidly decreases with increasing tilt angle theta between H and the c-plane (U(theta = 10 degrees) similar to 300 K. U(theta = 30 degrees) similar to 75 K). These angular dependences of the elastic modulus and the activation energy can be explained on the basis of the intrinsic pinning mechanism and the three-dimensional stepwise flux-line structure.
  • Takayuki Goto, Satoru Nakajima
    Physical Review B - Condensed Matter and Materials Physics, 54(5) 3562-3570, 1996  Peer-reviewed
    The end member of the Tl-based high-(Formula presented) cuprate (Formula presented)(Formula presented)(Formula presented) (Tl1212) with the zero nominal hole number has been synthesized and studied by Cu/Tl NMR. The existence of the antiferromagnetic ordering was demonstrated by the Zeeman-splitted zero-field Cu spectra. Static parameters at the Cu site such as the hyperfine field (Formula presented)=8.62 T and the quadrupolar frequency (Formula presented)=20.44 MHz were found to be comparable to other high-(Formula presented) related antiferromagnets (Formula presented)(Formula presented) and (Formula presented)(Formula presented)(Formula presented). The relaxation rate (Formula presented) of the Cu site of Tl1212 showed a significant deviation from the magnon theory, and was much smaller than (Formula presented)(Formula presented) and (Formula presented)(Formula presented)(Formula presented). The scaling between the temperature dependence of Tl (Formula presented) and Cu (Formula presented), the ratio of which was consistently explained with the hyperfine coupling constants determined by the analysis of spectra, showed that the relaxation is dominated by the 3d spin fluctuation. A possible relation between the spin fluctuation in the antiferromagnetic phase and the superconductivity in the high-(Formula presented) phase is also stated. © 1996 The American Physical Society.
  • T Fukase, M Kamata, T Hanaguri, T Sasaki, T Suzuki, T Goto, Tanaka, I, H Kojima
    PHYSICA B, 216(3-4) 274-276, Jan, 1996  
    The flux line lattice (FLL) elasticity and its anisotropic pinning have been investigated in a single crystalline La1.85Sr0.15CuO4, by ultrasonic measurements under high magnetic fields. The depinning activation energies are deduced from measurements under various settings of the directions of wave vector k, polarization vector a and magnetic fields H as U-ac(0 K, 14 T) = 972 K for H perpendicular to c, u parallel to c, U-ab(0 K, 14 T) = 201 K for H perpendicular to c, u parallel to(cxH) and U-ca(0 K, 14 T) = 25 K for H parallel to c, u perpendicular to c. The magnetic field dependence of U are also deduced as U(ac)proportional to H--0.3 and U(ca)proportional to H--1.5. The angular dependence of U-ac is discussed on the basis of the intrinsic pinning mechanism.
  • T Suzuki, K Chiba, T Goto, T Fukase
    CZECHOSLOVAK JOURNAL OF PHYSICS, 46(3) 1237-1238, 1996  
    The effect of magnetic field on the structural phase transitions at low temperature in La2-xSrxCuO4 has been investigated using the ultrasonic sound velocity experiment. An increase in the sound velocity V-s is observed below similar to 10K around x=0.12, which seems to be a precursor of the structural phase transition. This increase of V-s is drastically enhanced by applying a magnetic field. In case of x=0.120, the temperature where V-s shows the upturn shifts from 5K(H=OT) to 12K(H=15T), whereas,in x=0.160, V-s is not affected by magnetic fields up to 15T. These results suggest that the structure at low temperature (P-42/ncm or Pccn)in La2-xSrxCuO4 around x=0.12 is stabilized in magnetic fields.
  • T Goto, T Watanabe, K Kiinoshita, A Matsuda, M Sera, T Fukase
    CZECHOSLOVAK JOURNAL OF PHYSICS, 46(4) 2175-2176, 1996  
    The temperature dependence of Cu-NMR relaxation rate T-1(-1) and spectra have been measured for La-based high-T-c, cuprate La1.89Ca1.11Cu2O6+delta with the bilayer type of CuO planes. The shift showed a monotonic decrease with lowering temperature in the normal state, showing that this compounds belongs to the lightly doped region. The Curie Weiss temperature dependence of (T1T)(-1) down to T-c shows that the pseudo spin-gap does nor always exist in the bilayer systems.
  • T Goto, S Nakajima, M Kikuchi, Y Syono, T Fukase
    CZECHOSLOVAK JOURNAL OF PHYSICS, 46(4) 2173-2174, 1996  
    Cu-NMR study has been performed on the Zn-substituted TlBa2Ca(Cu1.xZnx)(2)O-7+delta belonging to the over-doped region. The temperature dependence of the Knight shift w as successfully explained in terms of the partially closed d-wave model proposed by Kitaoka et al. The reduction in T-c, by Zn-substitution was also consistent with Miyake's theoretical calculation on the potential scattering of the unitarity limit in the d-wave superconductors.
  • 後藤貴行
    物性研究, 64(6) 673-692, Sep, 1995  
  • GOTO TAKAYUKI
    11th International Conference, High Magnetic Fields in the Physics of Semiconductors, 440(3) xxxii+765, 1995  
  • T GOTO, K SEKI, S KAZAMA, H KOIZUMI, T FUKASE
    PHYSICA C, 235(3) 1663-1664, Dec, 1994  
    The high-T-c oxide La2-xBaxCuO4 shows a local minimum in the midst of the curve of T-c versus x around x congruent to 0.125, where the antiferromagnetic ordering and the structural phase transformation form the orthogonal phase to the tetragonal are reported to take place. In order to investigate the relation between these two phase transitions and the anomalous dip in T-c, Zn-concentration dependence of their transition temperatures has been studied by La-139-NMR and the ultrasonic attenuation. By Zn-substitution up to 6%, the Neel temperature showed significant reduction while the structural phase transformation temperature stayed almost constant, suggesting that these two are independent of each other.
  • T GOTO, S KAZAMA, T FUKASE
    PHYSICA C, 235 1661-1662, Dec, 1994  
    In order to investigate the origin of the anomalous dip in T-c at x congruent to 0.115 for La2-xSrxCuO4, the temperature dependence of Cu-63/65/La-139-NMR spectra has been studied on samples prepared by the spray-dry method. Spectra of Cu-63/65-NMR for the sample x congruent to 0.115 showed a huge broadening at 4.2 K, demonstrating the existence of the antiferromagnetic ordering of 3d-spins. The Neel temperature determined by La-139-NMR, showed maximum of T-N congruent to 32 K at x=0.115, which just coincided with the location of the dip in T-c, suggesting the crucial interplay between the antiferromagnetism and the suppression in T-c.
  • T GOTO, S KAZAMA, K MIYAGAWA, T FUKASE
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 63(9) 3494-3503, Sep, 1994  
    La-based high-T-c oxides La2-xBaxCuO4 (LBCO) and La2-xSrxCuO4 (LSCO) show a local minimum in the curve of T-c versus x around 0.125 for LBCO and around 0.115 for LSCO. in order to investigate the origin of this local minimum, temperature dependence of (CU)-C-63/65/La-139-NMR/NQR spectra has been studied on spray-dry-made samples with various Ba/Sr-concentrations. Existence of the antiferromagnetic ordering was confirmed by a significant broadening in the resonance lines at low temperatures below 35 K for LBCO (x congruent to 0.125) and 32 K for LSCO (x congruent to 0.115). By the analysis on the anisotropy in the broadening, the direction of the ordered field was found to be within the CuO plane. The hyperfine field and the Neel temperature showed a maximum at the Ba/Sr-concentration around which T-c is most suppressed, suggesting the crucial interplay between the antiferromagnetic ordering, and the suppression in T-c.
  • S KAWAJI, K HIRAKAWA, M NAGATA, T OKAMOTO, T FUKASE, T GOTOH
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 63(6) 2303-2313, Jun, 1994  
    Properties of the breakdown of the quantum Hall effect due to current have been measured in specially designed samples with the width ranging from 10 to 120 mum made from a Ga-As/AlGaAs heterostructure wafer at temperatures between 0.5 and 1.2 K in magnetic fields up to 23 T. Critical current in the onset of the breakdown is proportional to the sample width. The critical current density does not depend on temperature but depends on the Hall-plateau quantum number i for i = 1, 2 and 4 where R(H)(i)=h/ie2. Experimental results can be explained by production of dissipative carriers by inter-Landau-level transitions from the filled Landau level to the empty Landau level cuased by strong local electric fields in the extended states enhanced due to the localization.
  • S KAWAJI, K HIRAKAWA, M NAGATA, T OKAMOTO, T FUKASE, T GOTO
    SURFACE SCIENCE, 305(1-3) 161-165, Mar, 1994  
    Magnetic field dependence of the device-width-dependent breakdown current in the quantum Hall effect is measured in magnetic fields up to 23 T at 0.5 K for GaAs/AlGaAs Hall bars having a total length of 2900 mum, a source and drain-electrode width of 400 mum and different widths 10, 20 and 35 mum in its central 600 mum long part. Results are explained in terms of localization in Landau levels without edge-state transport.
  • K MIYAGAWA, T GOTO, T FUKASE
    PHYSICA B, 194(2) 2175-2176, Feb, 1994  
    The temperature dependence of La-139-NMR spectra has been studied on the copper oxide superconductor La2-xBaxCuO4 around x congruent-to 0.125, at which the superconductivity is anomalously suppressed. The significant broadening in resonance lines was observed below 35K, suggesting the antiferromagnetic phase transition of Cu 3d-spins. The analysis of the spectra has revealed that the internal field at La site is approximately 170 Oe, perpendicular to c-axis.
  • T GOTO, K MIYAGAWA, S NAKAJIMA, M KIKUCHI, Y SYONO, T FUKASE
    PHYSICA B, 194(2) 2179-2180, Feb, 1994  
    Zero-field spectra of the antiferromagnetic Cu-NMR have been observed on the Tl-based copper oxide TlBa2YCu2O7 (Tl1212). The internal field and the electric field gradient at Cu site have been found to be comparable to other antiferromagnetic phase of high-T(c) oxides. Hyperfine coupling constants of both Cu and Tl sites have been obtained through the analysis of Tl and Cu spectra.
  • M FUKUNAGA, T GOTO, K MIYAGAWA, T FUKASE
    PHYSICA B, 194(2) 2279-2280, Feb, 1994  
    All the electron-doped high-T(c) oxides discovered so far inevitably contain lanthanides, whose 4f-spin fluctuation hides all the NMR information on the superconductivity. The new copper oxide superconductor (La1-yYy)2-xCexCuO4 with T'-type structure, which is free from 4f-spins has been successfully synthesized. Obtained compounds showed a nearly zero electric field gradient(EFG) at Cu site, which demonstrates that the doped carrier is electronic.
  • T GOTO, S KAZAMA, K MIYAGAWA, M FUKUNAGA, T FUKASE
    PHYSICA B, 194(2) 2173-2174, Feb, 1994  
    The copper oxide superconductor La2-xSrxCuO4 shows x-T(C) curve with a small dip at x=0.115. In order to investigate the origin of this kink, the temperature dependence of La-139-NMR spectra has been studied. The significant broadening in the spectra was observed below 30K, suggesting the existence of the antiferromagnetic phase transition around x=0.115.
  • T. Suzuki, A. Fujita, K. Fukamichi, T. Goto
    Journal of Physics: Condensed Matter, 6(29) 5741-5750, 1994  
    The annealing effect on the magnetic phase diagram of the Y-Fe amorphous alloy system has been investigated by means of differential magnetic susceptibility. Y-Fe amorphous alloys annealed at 250 degrees C for 30 min exhibit a re-entrant spin-glass behaviour in a similar manner to the as-prepared samples in an applied magnetic field. The Curie temperature is enhanced but the spin-freezing temperature Tf is depressed by annealing. These facts suggest that the Fe-Fe interatomic distance, which significantly influences the magnetic properties, increases on annealing. The magnetic phase diagram of the Y-Fe amorphous alloy system in an applied magnetic field is similar to that of various re-entrant spin-glass-type Fe-based amorphous alloy systems in zero magnetic field.
  • GOTO TAKAYUKI, Shinohara Takeshi, Sato Takashi, Nakajima Satoru, Kikuchi Masae, Syono Yasuhiko, Miyagawa Kazuya, Fukase Tetsuo
    Advances in Superconductivity V, Springer-Verlag, 133-136, Aug, 1993  

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