NMR Investigations of the Static and Dynamic Properties of Spin Density Waves

自旋密度波的静态和动态特性的核磁共振研究

• 批准号: 9319304
• 负责人: W. Gilbert Clark
• 金额: $ 25.5万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-04-01 至 1997-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9319304&HistoricalAwards=false
• 关键词: NMR; Investigations; Static; Dynamic; Properties

9319304 Clark Technical abstract: The main issues addressed by this project are the static and dynamic properties of spin density waves (SDW) in anisotropic conductors. Nuclear magnetic resonance (NMR) spin echoes will be used as a microscopic probe, in conjunction with electrical transport. Most of the work will be on the Bechgaard salts (TMTSF)2X (X=PF6, ClO4, AsF6, etc.). Both "ordinary" and field induced spin density waves with varying degrees of pinning will be investigated. The physical quantities to be obtained from this work include the temperature dependence of the order parameter, the displacement of the condensate in response to an electrical field below threshold, its sliding velocity above threshold, the spatial and temporal distribution of the sliding velocity above threshold, SDW memory and repinning effects, and the temperature and frequency dependence of SDW phason fluctuations. Non-technical abstract: The purpose of this project is to investigate an unusual property of several organic materials that conduct electricity. At low temperatures the conducting electrons form a semiconducting state with an undulating magnetic structure called a spin density wave (SDW). This SDW is usually pinned to the underlying material imperfections. When, however, a small electric field above a certain threshold is applied to the material, the SDW slides. Under these conditions, it becomes a new type of electrical current. The measurements to be made are electrical conduction and nuclear magnetic resonance spin echo studies of the basic properties of these SDWs. They include the size of the undulating magnetic field, how its size varies with temperature, its thermal vibrations, how it moves when driven by an electric field, and the complex way it becomes pinned again when the electric field is removed. p:\wickman\abstract\clark.doc

9319304 Clark 技术摘要：该项目解决的主要问题是各向异性导体中自旋密度波（SDW）的静态和动态特性。核磁共振（NMR）自旋回波将与电传输结合用作显微探针。大部分工作将集中在 Bechgaard 盐 (TMTSF)2X（X=PF6、ClO4、AsF6 等）上。将研究具有不同钉扎程度的“普通”和场诱导的自旋密度波。从这项工作中获得的物理量包括序参数的温度依赖性、凝结体响应低于阈值的电场的位移、高于阈值的滑动速度、高于阈值的滑动速度的空间和时间分布， SDW 记忆和重新固定效应，以及 SDW 相子波动的温度和频率依赖性。 非技术摘要：该项目的目的是研究几种导电有机材料的不寻常特性。在低温下，导电电子形成半导体状态，具有称为自旋密度波（SDW）的波动磁结构。该 SDW 通常与底层材料缺陷有关。然而，当材料上施加高于特定阈值的小电场时，SDW 就会滑动。在这些条件下，它成为一种新型电流。要做的测量是对这些 SDW 基本特性的电导和核磁共振自旋回波研究。它们包括波动磁场的大小、其大小如何随温度变化、热振动、在电场驱动时如何移动，以及当电场移除时它再次被固定的复杂方式。 p:\wickman\abstract\clark.doc