研究者詳細 - 鄭　国慶

論文 - 鄭　国慶

分割表示 265 件中 241 - 260 件目／全件表示 >>

NMR Study in novel superconductors : Heavy Fermion and High - Tc Cuprate (共著)

Journal of Physics and Chemistry of Solids 56 ( 12 ) 1931 - 1935 1995年

Local Hole Distribution in the CuO₂ plane of High-Tc Cu-Oxides Studied by Cu and Oxygen NQR/NMR(共著)

J. Phys. Soc. Jpn. 64 ( 7 ) 2524 - 2532 1995年

NMR-STUDY OF SYMMETRY OF THE SUPERCONDUCTING ORDER-PARAMETER IN HIGH-T-C CUPRATE SUPERCONDUCTOR 査読

Y KITAOKA, K ISHIDA, GQ ZHENG, S OHSUGI, K YAMAZOE, K ASAYAMA

PHYSICA C 235 1881 - 1882 1994年12月

Magnetic-field enhancement of 63Cu and 17O relaxation rates in the mixed state of YBa2Cu4O8 observation of fermi-liquid state in the vortex cores

Guo-qing Zheng, Yoshio Kitaoka, Kunisuke Asayama, Yasuharu Kodama

Physica C: Superconductivity and its applications 227 ( 1-2 ) 169 - 175 1994年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

The 63Cu and 17O nuclear spin-lattice relaxation rates in YBa2Cu4O8 have been measured in the temperature and magnetic field ranges of 1.4-270 K and 4.0-11 T, respectively. In the mixed state, 1/T1 for both 63Cu and 17O are enhanced by the magnetic field. Most strikingly, in a high field of 11 T, 63(1/T1) and 17(1/T1) decrease in proportion to the temperature, T, below T=15 K and T=10 K, respectively. The magnetic-field dependence of 1/T1 is shown to be dominated by spin diffusion to the vortex cores, implying that the electronic state in the cores is characterized by the T1T=const. law. This result indicates that the electronic state in the vortex cores is described in terms of the Fermi-liquid picture, in sharp contrast to the unusual properties above Tc. © 1994.

DOI： 10.1016/0921-4534(94)90370-0

Scopus

researchmap

Cu NMR and NOR Studies of High-Tc Super conductor La_2-XSr_XCuO₄ 共著

Journal of Physical Society of Japan 63 ( 2 ) 700 - 715 1994年

Pressure dependence of Local Hole Distribution and Spin Correlation in La_1.85Sr_0.15CuO₄(共著)

235-240 ( 3 ) 1577 - 1578 1994年

⁶³Cu NMR study in high-T_c superconductor TlSr₂(Lu_1-xCa_x)Cu₂o_y 査読

K. Magishi, G.-q. Zheng, Y. Kitaoka, T. Kondo, Y. Shimakawa, T. Manako, Y. Kubo

Physica C: Superconductivity and its applications 235-240 ( PART 3 ) 1631 - 1634 1994年

CU-63 NMR-STUDY OF HEAVILY-DOPED SUPERCONDUCTOR TLSR2CACU2O7-GAMMA 査読

GQ ZHENG, K MAGISHI, Y KITAOKA, K ASAYAMA, T KONDO, Y SHIMAKAWA, T MANAKO, Y KUBO

PHYSICA B-CONDENSED MATTER 186-88 1012 - 1014 1993年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The Cu-63 Knight shifts have been measured for the heavily doped high-T(c) superconductors TlSr2CaCu2O7-y, with T(c) = 64 and 45 K. The spin part of the shift, K(s), is almost T-independent in the normal state and increases with decreasing T(c). From the analysis of the anisotropy in K(s) in both compounds, the transferred hyperfine field from the nearest-neighbor Cu spins has been deduced to be larger than that in YBa2Cu3O7, similar to the results for Tl2Ba2CuO6+y. A systematic correlation has been found in the heavily doped superconductors that the spin susceptibility and the nuclear quadrupole frequency increase with decreasing T(c), while 1/T1T is suppressed, as reported previously.

Web of Science

researchmap

¹⁷O NMR Study of La_2-XSr_xCuO₄ in the Lightly- and Heavily-Doped Regions 共著

Physica C 208 ( 3-4 ) 339 - 346 1993年4月

NMR in highly correlated superconductors 査読

K. Asayama, Y. Kitaoka, G. q. Zheng, K. Ishida, S. Ohsugi

Hyperfine Interactions 79 ( 1-4 ) 835 - 849 1993年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Kluwer Academic Publishers

Results of our systematic NMR study in high Tc cuprates are reviewed. The antiferromagnetic spin fluctuations (AFSF) decrease in the order of La1.85Sr0.15CuO4. YBa2Cu3O7 and Tl2Ba2CuO6+y. 1/T1 of63Cu in the CuO2 plane in the normal state follows essentially a Curie-Weiss law at high temperature and T1T = const. law at low temperature. The temperature dependence of 1/T1 and the Knight shift together with their impurity effect in the superconducting state strongly suggest d-wave pairing implying the AFSF to be responsible for the occurrence of superconductivity. From the NQR frequency measurement the density of Cu 3d and O 2p holes decreases and increases, respectively, in the order of La, Y and Tl compounds, which is consistent with the change of AFSF. The relation between Tc and vQ, and their pressure dependence suggest that there exists and optimum value of the ratio of Cu 3d and O 2p hole density to give a maximum in Tc. © 1993 J.C. Baltzer AG, Science Publishers.

DOI： 10.1007/BF00567615

Scopus

researchmap

NMR and NQR Studies of Spin Correlation and Superconductivity in High-Tc Oxides(共著)

J. Phys. Chem. Solids. 54 ( 10 ) 1385 - 1392 1993年

⁶³Cu NQR/NMR Study of Zn-Substituted YBa₂Cu₄O₈ -Effect of Impurity on Spin-Gap-Like Behavior- 共著

Journal of Physical Society of Japan 62 ( 8 ) 2591 - 2594 1993年

NMR in Highly Correlated Superconductors. (共著)

Hyperfine Interaction 79 ( 1-4 ) 835 - 849 1993年

¹⁷O NMR Study of L₁₀cal Hole Density and Spin Dynamics in YBa₂Cu₄O₈ 共著

Physica C 193 ( 1-2 ) 154 - 162 1992年4月

NQR AND NMR IN HIGH-TC SUPERCONDUCTORS 査読

K ASAYAMA, Y KITAOKA, GQ ZHENG

ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES 47 ( 1-2 ) 7 - 11 1992年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：VERLAG Z NATURFORSCH

Recent NQR and NMR experiments on La2-xSrxCuO4, YBa2Cu3O7, Tl2Ba2CuO6+y and other compounds are reviewed. The antiferromagnetic spin fluctuations decrease in the order of La, Y, Tl compounds. In the normal state the T-dependence of (T1T)-1 is considered to follow the Curie-Weiss law at high temperature and the (T1T) = const law at low temperature. The T dependence of 1/T1 below T(c) suggests strongly d-wave pairing. Correlations of the NQR frequency of Cu-63 and O-17 with the antiferromagnetic spin fluctuations and the superconducting transition temperature are discussed.

Web of Science

researchmap

CORRELATION BETWEEN TC AND THE HOLE DENSITY AT CU AND OXYGEN 査読

GQ ZHENG, E YANASE, K ISHIDA, Y KITAOKA, K ASAYAMA, Y KODAMA, S ENDO

PHYSICA C 185 767 - 768 1991年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Dependence of NQR frequency, nu-Q(Cu) on pressure up to 1.3GPa is reported for La1.85Sr0.15CuO4 and YBa2Cu4O8. Correlations are found between some physical quantities and the ratio of the hole density in Cu2 to that in O2(3), n(Cu2)/n(O2, 3) which is extracted from nu-Q's. It is proposed tha there exists an optimum of n(Cu2)/n(O2, 3) for T(c) and that the increase of T(c) under pressure is due to the approach of n(Cu2)/n(O2, 3) to the optimum through the local hole transfer.

Web of Science

researchmap

O-17 AND CU-63 NMR INVESTIGATIONS OF HIGH-TC SUPERCONDUCTOR LA1.85SR0.15CUO4 WITH TC = 38-K 査読

K ISHIDA, Y KITAOKA, GQ ZHENG, K ASAYAMA

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 60 ( 10 ) 3516 - 3524 1991年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOCIETY JAPAN KIKAI-SHINKO BUILDING

O-17 and Cu-63 NMR measurements have been made in L1.85Sr0.15CuO4 with T(c) = 38 K. Both O-17 Knight shift and quadrupole tensor were determined from the analyses of the O-17 spectrum of oriented powder. The quadrupole frequencies of the planar oxygen and Cu nuclei are consistently interpreted by the analyses of Hanzawa et al. made in YBa2Cu3O7 with the electric field gradients due to the on-site holes at Cu and O sites. Then the weight factor of the Cu-3d(x2 - y2) and 2p-sigma wave functions are deduced, the latter having the larger weight. From the Knight shifts vs the bulk susceptibility plots, the hyperfine coupling constants for O-17 and Cu-63 were almost the same as those in YBa2Cu3O7. Both shifts decrease significantly below T(c) having residual parts of 63K(ab) = 0.38% and 17K(c) = 0.02% at 4.2 K, which were larger than those in YBa2Cu3O7.

Web of Science

researchmap

NMR Investigation of High Tc superconductors under Pressure 共著

Solid State Commu. 79 ( 1 ) 51 - 55 1991年

NQR study of high-T_c superconductor TlSr₂CaCu₂O_7-δ 査読

G.-q. Zheng, Y. Kitaoka, K. Asayama, T. Kondo, Y. Shimakawa, T. Manako, Y. Kubo

Physica C: Superconductivity and its applications 185-189 ( PART 2 ) 765 - 766 1991年

Proximity-Effect-Induced Superconductivity and NMR Relaxation in Na-Cu Multilayered thin Films 共著

J. Phys. Soc. Jpn. 60 ( 2 ) 599 - 607 1991年

　前のページ - 次のページ　

<鄭 国慶>

論文 - 鄭 国慶

<鄭　国慶>

論文 - 鄭　国慶