NMR Studies of Structural Phase Transitions of Quasi one-dimensional Jahn-Teller Crystals

准一维 Jahn-Teller 晶体结构相变的核磁共振研究

• 批准号: 62540246
• 负责人: HAUO NIKI
• 金额: $ 0.96万
• 依托单位: University of the Ryukyus
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1987
• 资助国家: 日本
• 起止时间: 1987 至 1988
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62540246/
• 关键词: Nuclear Magnetic Resonance (NMR); Nuclear Quadrupole Resonance (NQR); Low Dimensional Magnetic Materials; Structural Phase Transition; ヤーンーテラー効果; ヤーン-テラー効果; 核磁気共鳴; 核四重極共鳴

The ABX_3 type of Jahn-Teller crystal such as CsCuCl_3 and RbCuCl_3 undergo structural phase transition which has been studied microscopically by NMR and NQR. Since the change of physical properties induced by the phase transition is revealed by the frequency, line width and relaxation time of resonance, accurate measurement of these quantities is necessary. Since the Cu atom is par-amagnetic in room temperatures, line width and relaxation time of resonance signal of each atom are broader than those of non-magnetic substances by the order of 10. Moreover, since measurement at high temperatures are required, it was urgent to improve S/N ratio, necessarily resulting in construction and improvement of NMR and NQR apparatus. Following are two features in constructing and improving the apparatus 1) Development of a marginal oscillator capable of wide-line and automatic measurement. 2) Construction of apparatus for NMR and NQR for pulse method. These apparatus were employed in NMR measurements of ^1H nucleus of high temperature superconductor YBa_2Cu_3O_7- H_<0.2>. The magnetic field penetration depth can be de-termined from the temperature dependence of NMR line width and the knowledge of spin-lattice relaxation time T_1 has been acquired. Moreover, use of the apparatus for Cl NQR in Chloral Iso-Butylhemiacetal has given much knowledge about lattice defect. The study of Jahn-Teller crystals CsCuCl_3 and RbCuCl_3 and clarification of the origin of their structural phase transitions will be extensively continued.

ABX_3型Jahn-Teller晶体如CsCuCl_3和RbCuCl_3经历结构相变，已通过NMR和NQR在显微镜下研究。由于相变引起的物理性质的变化是通过共振的频率、线宽和弛豫时间来揭示的，因此需要精确测量这些量。由于Cu原子在室温下是顺磁性的，因此各原子的共振信号的线宽和弛豫时间比非磁性物质宽10个量级。此外，由于需要在高温下进行测量，因此迫切需要提高信噪比，必然需要NMR和NQR装置的建设和改进。以下是该装置构造和改进的两个特点： 1）开发了能够宽线自动测量的边际振荡器。 2)脉冲法NMR、NQR装置的构建。这些装置用于高温超导体YBa_2Cu_3O_7-H_ 0.2 的^ 1 H核的NMR测量。磁场穿透深度可以根据NMR线宽的温度依赖性来确定，并且已经获得了自旋晶格弛豫时间T_1的知识。此外，氯醛异丁基半缩醛中Cl NQR装置的使用提供了很多关于晶格缺陷的知识。对Jahn-Teller晶体CsCuCl_3和RbCuCl_3的研究以及对其结构相变起源的澄清将继续广泛进行。

项目成果

Haruo NIKI: "Nuclear Spin-Lattice Relaxation of ^1H in YBa_2Cu_3O_<7- >H_<0.2>" Journal of The Physical Society of Japan.

Haruo NIKI：“YBa_2Cu_3O_<7->H_<0.2> 中 ^1H 的核自旋晶格弛豫”日本物理学会杂志。

Haruo NIKI: "Construction of Signal Averager using Wave Memory and Microcomputer (II)" Bulletin of The College of Science Universityof The Ryukyus. 45. 19-38 (1987)

Haruo NIKI：“使用波存储器和微型计算机构建信号平均器（II）”琉球理科大学学院通报。

Haruo NIKI: "Computer-Enhanced Wide-Line NQR Spectrometer of Marginal Oscillator-Detector Type using Field Effect Transistors" Kaiho-Kagaku PC Kenkyukai.

Haruo NIKI：“使用场效应晶体管的边缘振荡器检测器型计算机增强宽线 NQR 光谱仪”Kaiho-Kagaku PC Kenkyukai。

Haruo,Niki.: Journal of the Physical Society of Japan.

Haruo，Niki。：日本物理学会杂志。

Haruko NIKI: Journal of Molecular Structure.

Haruko NIKI：分子结构杂志。