Observation of Local Field Distribution in the Mixed State of Cuprate Superconductor through ESR Experiments

通过ESR实验观察铜酸盐超导体混合态的局域场分布

• 批准号: 07640496
• 负责人: NISHIDA Akihiko
• 金额: $ 0.32万
• 依托单位: Fukuoka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640496/
• 关键词: cuprate superconductor; mixed state; local field distribution; ESR; spin probe; vortex fluctuation; inhomogeneity; 不可逆特性; 不均一幅; 磁場侵入長

Temperature dependence of Cu^<2+> ESR in Tl_2Ba_2Ca_2Cu_3O_<10> superconductor was meqsured, and various anomalies of the spectroscopic g factor, linewidth and intensity were observed. The g factor began to decrease below the transition temperature T_c, the phenomena being explained by the superconducting shielding effect against the external field. On the other hand, the linewidth was observed to broaden below the flux melting temperature T_m rather than T_c, and interpreted with the frozen local field inhomogeneity in the mixed state. The motional narrowing was suggested between T_m and T_c. The ESR intensity also indicated drastic decrease below T_c with more enhanced reduction at lower modulation frequencies, and attributed to energy dissipation due to viscous flux motion.Next, sintered, single crystalline and oriented YBa_2Cu_3O_<7-delta> samples were prepared, and ESR of the DPPH free radical applied on each sample surface was observed (spin probe method) in order to investigate … More various factors contributing to the local field inhomogeneity and distribution. Asymmetrically broadened lineshape just below T_c for the sintered pellet evolved into clear double peak structures at lower temperatueres. The ESR parameters for the individual peaks were then evaluated with computer simulations and lineshape fittings. Combined examinations of temperature dependent ESR parameters with scanning micro-probe analyzes revealed large contribution of sample inhomogeneity (steady and weak superconductivity) to the line broadening as dominant one rather than the ideal field distribution in the mixed state. More enhanced ESR broadening was observed corresponding to the fine structures for the oriented sample, while broadening for the single crystal was fairly mild, indicating applicability and effectiveness of the present spin-probe method.Related measurements of magnetization and resistivity as well as ESR on Mn-doped Y-based superconductor were performed along with comprehensive examinations on the peculiar flux behaviors and characteristic local field variations in Suprate superconductors. Less

测量了Tl2Ba2Ca2Cu3O&lt；10&gt；超导体中Cu2+&gt；ESR随温度的变化，观察到了光谱g因子、线宽和强度的各种反常现象。G因子在转变温度T_c以下开始下降，这可以用超导对外场的屏蔽效应来解释。另一方面，在熔剂熔化温度T_m而不是T_c以下观察到线宽变宽，并用混合态冻结的局域场不均匀来解释。其次，制备了烧结型、单晶型和取向YBa2Cu3O7-β-…样品，并用自旋探针法观察了样品表面DPPh自由基电子自旋共振的情况更多的各种因素导致了局部场的不均匀和分布。T_c以下的非对称展宽线型在较低温度下演化为清晰的双峰结构。然后通过计算机模拟和线型拟合来评估各个峰的ESR参数。结合随温度变化的ESR参数和扫描微探针分析表明，样品的不均匀性(稳态和弱超导电性)对谱线展宽的贡献很大，而不是混合态的理想场分布。与取向样品的精细结构相对应，ESR展宽得到了更多的增强，而单晶的展宽相对较小，这表明了自旋探针方法的适用性和有效性。对掺锰Y基超导体的磁化强度、电阻率以及ESR进行了相关测量，并对超导体特有的磁通行为和特征的局域场变化进行了全面的研究。较少

项目成果

Akihiko Nishida: "ESR Lineshape Simulation Studies on Polycrystalline Materials with Axial Symmetry" Fukuoka Univ. Sci. Rep.25. 89-98 (1995)

西田明彦：“轴对称多晶材料的 ESR 线形模拟研究”福冈大学。

Akihiko Nishida: "Vortex Dynamics and Frequency-Dependent ESR Anomalies in Tl_2Ba_2Ca_2Cu_3O_<10>" Advances in Superconductivity. 8. 591-594 (1996)

Akihiko Nishida：“Tl_2Ba_2Ca_2Cu_3O_<10> 中的涡动力学和频率相关 ESR 异常”超导进展。

Akihiko Nishida: "ESR Observations in Mn-Doped YBa_2Cu_3O_<7-δ> Superconductors" Advances in Superconductivity. 10(in press). (1998)

Akihiko Nishida：“Mn 掺杂 YBa_2Cu_3O_<7-δ> 超导体的 ESR 观察”《超导进展》10（出版中）。

A.Nishida, C.Taka and K.Horai: ""ESR Observations in Mn-Doped YBa_2Cu_3O_<7-delta> Superconductors"" Advances in Superconductivity. 10 (in press). (1998)

A.Nishida、C.Taka 和 K.Horai：“Mn 掺杂 YBa_2Cu_3O_<7-delta> 超导体中的 ESR 观察””超导性进展。

Akihiko Nishida: "Field Inhomogeneity at the Surface of YBa_2Cu_3O_<7-δ> and eSR Anomalies" Advances in Superconductivity. 9. 475-478 (1997)

Akihiko Nishida：“YBa_2Cu_3O_<7-δ> 表面的场不均匀性和 eSR 异常”超导进展 9. 475-478 (1997)。