Anomalous Physical Properties of Strongly Correlated Electron System with Frustration and Spin Chirality

具有挫败和自旋手性的强相关电子系统的反常物理性质

• 批准号: 14340103
• 负责人: SATO Masatoshi
• 金额: $ 8.96万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340103/
• 关键词: spin chirality; anomalous Hall effect; spin glass; frustration; superconductivity; NMR; pyrochlore system; spinel system; Ns_xCoO_2・yH_2O; Nd_2Mo_2O_7; non-trivial magnetic structure

Studies focused mainly on strongly correlated electrons with geometrical frustration have been carried out. (i)Unusual behaviors of the anomalous Hall resistivity(AHR) of ferromagnetic systems with non-trivial magnetic structure have been studied to clarify if the behavior is related to the ordering of spin chirality χ locally defined for three spins S_1, S_2 and S_3 as χ≡S_1(S_2×S_3). Ground states of frustrated spin systems have been studied experimentally for various pyrochiore type oxides. (ii) Superconductivity of Na_xCoO_2・yH_2O has been studied mainly by means of NMR. (iii)We have also studied the physics of high-T_c Cu oxides mainly by studying the characteristics of their magnetic excitation spectra.To see the origin of unusual behaviors of AHR of Nd_2Mo_2O_7, the magnetic structure has been analyzed as a function of the applied magnetic field Hand the H-dependence of the chirality (or AHR) has been directly calculated from the obtained results. Mo→Ti substitution effects on the behaviors of the AHR has also been studied. The results of these studies clearly indicate that the chiral order mechanism proposed theoretically does not, at least, have a primary role in determining the behavior of the AHR of Nd_2Mo_2O_7. In the study on AHR of a reentrant spin glass system Fe_<1-x>Al_x, it has been shown that the uniform chirality induced by the coupling of the frozen chirality with the uniform magnetization contributes to AHR. In the study on so-called spin ice system, Ho_2Ti_2O_7, we hav.e shown what kind of spin correlation this strongly frustrated spin system has at T→0.To clarify if the superconductivity of Na_xCoO_2・yH_2O with triangular lattice of CoO_2, The NQR 1/T_1T and the NMR Knight shift K have been measured, where a very small (or no) coherence peak of 1/T_1T and the decrease of K have been observed. Extensive studies are now being carried out.

研究主要集中在强关联电子的几何挫折已经进行。（i）研究了具有非平凡磁结构的铁磁系统的反常霍尔电阻率（AHR）的反常行为，以阐明这一反常行为是否与三个自旋S_1，S_2，S_3的自旋手征性χ的有序性有关：χ <$S_1（S_2×S_3）。实验研究了不同烧绿石型氧化物的自旋阻挫系统的基态。(ii)本文主要用NMR研究了Na_xCoO_2·yH_2O的超导电性。（iii）我们还研究了高T_cCu氧化物的物理性质，主要是研究了它们的磁激发谱的特征，分析了Nd_2Mo_2O_7的磁结构与外加磁场的关系，并根据所得结果直接计算了手征度（或AHR）与H的关系，以了解Nd_2Mo_2O_7的AHR异常行为的根源。研究了Mo→Ti替代对AHR性能的影响。这些研究结果清楚地表明，理论上提出的手征有序机制至少在决定Nd_2Mo_2O_7的AHR行为方面不起主要作用。在对重入自旋玻璃Fe_ Al_x的AHR研究中<1-x>，我们发现，由冻结手征与均匀磁化耦合而产生的均匀手征对AHR有贡献。在对自旋冰系统Ho_2Ti_2O_7的研究中，我们揭示了这种强阻挫自旋系统在T→ 0时的自旋关联。为了阐明具有CoO_2三角晶格的Na_xCoO_2·yH_2O的超导电性，我们测量了NQR 1/T_1T和NMR Knight位移K。其中观察到很小（或没有）的1/T_1T相干峰和K的降低。目前正在进行广泛的研究。

项目成果

K.Tsuchida et al.: "Ru-NMR Studies and Specific Heat Measurements of Bi_3Ru_3O_<11> and La_4Ru_6O_<19>"J.Phys.Soc.Jpn.. 73 No.3. 698-702 (2004)

K.Tsuchida等人：“Bi_3Ru_3O_<11>和La_4Ru_6O_<19>的Ru-NMR研究和比热测量”J.Phys.Soc.Jpn..73 No.3。

T.Miyashita: "^<59>Co-NMR Studies on La_4Co_3O_<10+δ>"J.Phys.Soc.Jpn.. 71No.12. 3043-3046 (2002)

T.Miyashita：“La_4Co_3O_<10+δ>的^<59>Co-NMR研究”J.Phys.Soc.Jpn..71No.12(2002)。

M.Ito et al.: "Effects of "Stripes" on the Magnetic Excitation Spectra of La_<1.48>Nd_<0.4>Sr_<0.12>CuO_4"J.Phys.Soc.Jpn.. 72 No.7. 1627-1630 (2003)

M.Ito 等人：““条纹”对 La_<1.48>Nd_<0.4>Sr_<0.12>CuO_4 磁激发光谱的影响”J.Phys.Soc.Jpn.. 72 No.7。

T.Kageyama: "Anomalous Hall Effect of Reentrant Spin Glass State Fe_<1-X>Al_X(X〜0.3)"J.Phys.Soc Jpn.. 72 No.6. 1491-1494 (2003)

T.Kageyama：“重入自旋玻璃态 Fe_<1-X>Al_X(X〜0.3) 的反常霍尔效应” J.Phys.Soc Jpn.. 72 No.6 (2003)

S.Iikubo: "Magnetic Structure and the Anomalous Hall Effect of Cu_<1-X>Zn_XCr_2Se_4"Physica B. 329-333. 707-709 (2003)

S.Iikubo：“Cu_<1-X>Zn_XCr_2Se_4 的磁性结构和反常霍尔效应”Physica B. 329-333。