Relationship between unconventional superconducting phase and magnetic phase in strongly correlated electron compounds

强关联电子化合物中非常规超导相与磁相的关系

• 批准号: 18340102
• 负责人: ISHIDA Kenji
• 金额: $ 10.7万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2006
• 资助国家: 日本
• 起止时间: 2006 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18340102/
• 关键词: strongly correlated electron system; Cobaltate; Cuprate; Unconventional sunerconductivity; Magnetism; NMR; NQR; uSR; 銅酸化物超伝導; コバルト酸化物

During this research project, we have performed NMR and nuclear quadrupole resonance (NQR) on various strongly correlated electron compounds in order to investigate superconducting properties and spin dynamics in the normal state. Especially, bilayered hydrate (BLH) cobaltate superconductors (Na_x(H_3O)_zCoO_<2-y>H_2O) and cuprate superconductors (La_<2-x>Sr_xCuO_4) are intensively studied.1) Co NMR/NQR Studies on Na_x(H_3O)_zCoO_<2y>H_2OWe found a weak magnetism in a nonsuperconducting BLH cobaltate sample with Co-NQR measurements. This sample shows the divergence of 1/T_1 T at T_M〜5.5 K, below which the Co-NQR spectrum is broadened due to the appearance of the internal field at the Co site. We also found that the NQR frequency v_〓 correlates with magnetic fluctuations just above T_c from measurements of NQR spectra and 1/TlT in more than 10 BLH samples with various T_c and T_M. Phase diagram of BLH cobaltate superconductors was developed by plotting T_c and T_M against v_〓. It was shown that superconductivity with the highest T_c is observed in the vicinity of a magnetic phase, suggesting that magnetic fluctuations play an important role in the occurrence of unconventional superconductivity.2) Static magnetism and superconductivity in La_<2-x>,Sr_xCuO_4Relationship between magnetism and superconductivity was investigated with transverse-field (TF) μSR in La_<1.93>Sr_<0.07>CuO_4 (T_c〜17 K), which is close to the border of two phases. We found the occurrence of the static magnetism at T_g〜4K far below T_c. The magnetic volume fraction was estimated to be more than 90 %. We conclude that the static magnetism with staggered correlation coexists with superconductivity.

在这个研究项目中，我们对各种强相关电子化合物进行了核磁共振和核四极共振（NQR），以研究正常状态下的超导特性和自旋动力学。特别是双层水合物(BLH)钴酸盐超导体(Na_x(H_3O)_zCoO_<2-y>H_2O)和铜酸盐超导体(La_<2-x>Sr_xCuO_4)得到了深入研究。1)Na_x(H_3O)_zCoO_<2y>H_2O的Co NMR/NQR研究我们发现 使用 Co-NQR 测量非超导 BLH 钴酸盐样品中的弱磁性。该样品在T_M〜5.5 K处显示出1/T_1 T的发散，低于该发散度，由于Co位点处内场的出现，Co-NQR光谱变宽。我们还发现，在具有不同 T_c 和 T_M 的 10 多个 BLH 样本中，通过测量 NQR 谱和 1/TlT，NQR 频率 v_〓 与略高于 T_c 的磁波动相关。 BLH 钴酸盐超导体的相图是通过绘制 T_c 和 T_M 与 v_〓 的关系图来绘制的。结果表明,在磁相附近观察到了最高T_c的超导性,表明磁涨落在非常规超导的发生中发挥了重要作用。2)La_<2-x>,Sr_xCuO_4中的静态磁性与超导性利用横向场(TF)μSR研究了磁性与超导性的关系。 La_<1.93>Sr_<0.07>CuO_4 (T_c〜17 K)接近两相边界。我们发现静磁发生在远低于T_c的T_g〜4K。磁性体积分数估计超过90%。我们得出结论，交错关联的静磁性与超导性共存。

项目成果

Co-NMR Measurements on crystalline sample of the bilayered hydrate Na_x(H_3O)_zCoO_2・yH_2O

双层水合物Na_x(H_3O)_zCoO_2·yH_2O晶体样品的Co-NMR测量

• 发表时间: 2008
• 期刊: Journal of Physical Society of Japan 77(印刷中)
• 作者: Y. Ihara;K. Ishida;H. Ohta and K. Yoshimura
• 通讯作者: H. Ohta and K. Yoshimura

Phase diagram for Na_x(H_3O)_zCoO_<2y>H_2O

Na_x(H_3O)_zCoO_<2y>H_2O 相图

• 发表时间: 2007
• 期刊: New Research on Superconductivity, NOVA Science Publishers, Inc
• 作者: Y.;Ihara;K.;Ishida;H.;Sakurai;E.;Takayama-Muromachi
• 通讯作者: Takayama-Muromachi

Magnetic Correlations and Superconductivity in La_<2-x>Sr_xCuO_4 TF-uSR Study

La_<2-x>Sr_xCuO_4 TF-uSR研究中的磁相关性和超导性

• 发表时间: 2006
• 作者: K.;Ishida
• 通讯作者: Ishida

Phase diagram in bilayered-hydrate Na_xCoO_<2-y>H_2O revealed by Co nuclear quadrupole resonance

Co核四极共振揭示双层水合物Na_xCoO_<2-y>H_2O相图

• 发表时间: 2006
• 期刊: Physica B-Cond Matter 378-80
• 作者: K.;Ishida;Y.;Ihara;H.;Takeya;C.;Michioka;K.;Yoshimura;K.;Takada;T.;Sasalci;H.;Salcurai;E.;Takayama-Muromachi
• 通讯作者: Takayama-Muromachi

Magnetic Correlations and Superconductivity in La_<2-x>Sr_xCuO_4 TF-μSR Study

La_<2-x>Sr_xCuO_4 TF-μSR研究中的磁相关性和超导性

• 发表时间: 2007
• 作者: 三上史記;松田和之;真庭豊;石田憲二
• 通讯作者: 石田憲二