Spectroscopy of Pressure- and Field-Induced Insulator-Metal Transitions: Exploring Charge- and Spin-Organization in Complex Oxides and Magnetic Semiconductors

压力和场引起的绝缘体-金属转变的光谱学：探索复杂氧化物和磁性半导体中的电荷和自旋组织

• 批准号: 0244502
• 负责人: S. Lance Cooper
• 金额: --
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0244502&HistoricalAwards=false
• 关键词: Spectroscopy; Pressure; Field; Induced; Insulator

There is now strong evidence that some of the most scientifically interesting and technologically promising phenomena exhibited by correlated systems occur near low temperature phase boundaries. These phenomena include the spontaneous organization of mesoscale charge, spin, and orbital structures, and "colossal" sensitivities of physical properties to applied pressure and magnetic field. A better understanding of these exotic phenomena demands greater insight into how the low energy dynamical properties evolve across the low temperature phase transitions of these materials. This individual investigator award supports research that utilizes a unique method for using inelastic light scattering to spectroscopically explore - in a way not previously possible - the important evolution of the spin, charge, and lattice dynamics of correlated systems while pressure- and/or field-tuning through low temperature phase transitions. The principle focus of this study will be on two classes of phenomena: (A) Quantum phase transitions in complex oxides, to study the evolution and effects of spontaneous charge-, spin-, and orbital-organization near low temperature phase transitions. (B) Spin electronics in magnetic semiconductors, to explore the evolution and impact of magnetic cluster formation near phase transitions. Not only will this research afford critical information about the dynamics near various low temperature phase transitions of technologically important materials, but it will provide the scientific community a greater understanding of the limitations and benefits of applying low-temperature/high-pressure light scattering for studying phase transitions and extreme phase regimes in a variety of systems. Further, this project will train graduate student and postdoctoral researchers in cutting-edge pressure and spectroscopic techniques, eventually adding to the technical base of the country.Intensive recent research has uncovered a variety of functional materials exhibiting scientifically important phenomena with technologically promising properties, e.g., in magnetic storage devices, magnetic sensors, switches, etc. These exotic properties include extremely large sensitivities of the electrical properties to the application of magnetic fields ("colossal" magnetoresistance), and abrupt magnetic field- and pressure-sensitive transitions between electrically-conducting and -non-conducting phases. It is now believed that these exotic properties are likely caused by the spontaneous formation of nanometer-scale structures when these materials transition between conducting and non-conducting phases; however, the nature of this causal connection needs to be significantly elucidated before scientists can understand how best to design these materials for technological advantage. This individual investigator research project will utilize a unique method in which laser light is used to study how the magnetic-field- and pressure-dependent evolution of nanometer-scale structures give rise to the dramatic and technologically-useful properties in complex oxides and spin-electronic materials. The information that will be obtained with this project is an essential prerequisite to the effective design and utilization of these materials as devices. Further, this project will train graduate student and postdoctoral researchers in cutting-edge pressure and spectroscopic techniques, eventually adding to the important technical base of the country.

现在有充分的证据表明，相关系统表现出的一些最科学有趣和技术上有希望的现象发生在低温相边界附近。 这些现象包括中尺度电荷，自旋和轨道结构的自发组织，以及对施加压力和磁场的物理特性的“巨大”敏感性。 更好地理解这些异国情调现象，需要更深入地了解这些材料的低温相变跨低温动力学特性如何发展。 该个别研究者奖支持了使用一种独特的方法，该研究利用一种使用非弹性光散射来探索光谱 - 以前是不可能的 - 与相关系统的自旋，电荷和晶格动态的重要演变，而通过低温相变量进行压力和/或场调节。 这项研究的主要重点将放在两类现象上：（a）复杂氧化物中的量子相变，以研究自发电荷，自旋 - 自旋和轨道 - 和轨道 - 在低温度相变的附近的进化和影响。 （b）磁性半导体中的自旋电子学，以探索磁簇形成在相变附近的演化和影响。 这项研究不仅将提供有关技术重要材料各种低温相变的动力学的关键信息，而且还将为科学界提供对应用低温/高压光散射的局限性和好处的更多了解，以研究各种系统中的极端相变和极端相位方案。 此外，该项目将培训研究生和博士后研究人员在最先进的压力和光谱技术方面，最终增加了该国的技术基础。最近的研究发现了各种功能性材料，这些功能材料具有科学意义的现象，具有技术上有希望的特性，例如，这些磁性特性，包括磁性储存器件，磁性传感器，磁性传感器，磁性感官，磁性传感器，磁性感官，磁性感官，磁性型，磁性感官，磁性感官，磁性感官，磁性感官，磁性感官，磁性型，传感器，传感器，传感器，传感器，传感器，传感器，传感器，磁性材料，磁性材料，磁性材料。 （“巨大”的磁磁性），以及电磁场和 - 导向相之间的突然磁场和压力敏感性的过渡。 现在，人们认为这些外来特性可能是由于这些材料在导电和非导向阶段之间的材料过渡时的自发形成而引起的。但是，在科学家才能理解如何最好地设计这些材料以获得技术优势之前，需要显着阐明这种因果关系的性质。 该单独的研究者研究项目将利用一种独特的方法，在该方法中，激光光用于研究纳米尺度结构的磁场和压力依赖性的演化如何产生复杂氧化物和自旋电子材料中戏剧性和技术使用的特性。 该项目将获得的信息是将这些材料作为设备有效设计和利用的必要先决条件。 此外，该项目将培训研究生和博士后研究人员的尖端压力和光谱技术，最终增加了该国重要的技术基础。