GOALI: Spin-Transfer in Magnetic Nanostructures

摘要：该项目汇集了来自纽约大学和IBM的顶尖研究人员，旨在进一步了解和应用纳米级磁性器件和材料。磁性纳米结构在信息处理领域的应用最为广泛。由于世界范围内对数据处理和存储的需求不断增长，它们在美国形成了一个庞大产业的支柱。美国工业和大学实验室在这一领域的创新研究保持了我们在这一重要领域的世界领先地位。人们已经发现，在微型磁性器件中，直流电可以通过一种称为自旋转移的机制来改变磁化方向。这是一项令人兴奋的发展，可能会使磁性信息处理和存储方面取得巨大进步。关于电流和磁化之间相互作用的本质，有一些重要而基本的问题，这个项目将通过使用纽约大学独特的高频测量技术和美国国家实验室可用的磁成像方法，研究自旋电流激发的磁性纳米结构来解决。这项研究将与磁学研究前沿领域年轻科学家的培训相结合。参与这项合作的研究生和本科生将通过学术界和工业界的互动以及纽约大学和IBM之间的交流获得经验。通过接触工业环境中的各种观点、专业知识和技术，他们的教育将得到丰富。高中生也将参与这项研究。技术摘要：这个NSF-GOALI项目汇集了来自纽约大学和IBM的纳米磁学领域的顶尖研究人员，旨在进一步了解自旋转移的物理学。自旋转移是一种机制，通过自旋极化电流可以扭转纳米磁体的磁取向，并引起磁激励，如自旋波。了解自旋转移引起的自旋激发的性质是目前研究的一个非常活跃的领域。本研究旨在促进对自旋转移相互作用产生的两种类型的集体自旋激发的理解和应用：磁孤子，这是在纳米尺度电接触中激发到磁性薄膜的局部自旋激发，以及在易平面磁层中激发的超自旋电流。关于磁孤子的寿命，动力学和相干度的基本问题将在实验中解决，其中孤子动力学可以通过外部扰动（例如应用场和电流）来控制。扫描透射x射线显微镜将用于成像磁化动力学，以提供电流诱导自旋激发性质的直接信息。平行的理论工作将探索温度和其他扰动的影响，以及受限几何对孤子寿命和动力学的影响，并将探索非拓扑和拓扑状态之间的转换。超自旋电流将在由近端纳米接触组成的样品中进行探索，用于自旋电流的注入和检测。这些实验旨在证明和评估这种新提出的自旋输运机制的有效性。参与这项合作的研究生和本科生将通过学术界和工业界的互动以及纽约大学和IBM之间的学生交流获得经验。他们的教育将通过这个综合实验和理论项目，以及在工业环境中出现的各种观点，专业知识和技术而丰富。高中学生也将被鼓励参与这个研究项目。

Non-Technical Abstract:This project brings together leading researchers from New York University and IBM with the aim of furthering the understanding and application of nanometer scale magnetic devices and materials. Magnetic nanostructures are widely used in technology with the most advanced applications found in information processing. Because of ever-increasing worldwide demands for data processing and storage, they form the backbone of a huge industry in the United States. Innovative research in this area at U.S industrial and university laboratories has maintained our world leadership in this vital area. It has been discovered that in miniature magnetic devices a direct electrical current can switch the direction of magnetization by a mechanism known as spin-transfer. This is an exciting development that may enable dramatic improvements in magnetic information processing and storage. There are important and fundamental questions about the nature of the interaction between the current and magnetization that this project will address through studies of magnetic nanostructures excited by spin-currents using unique high frequency measurement techniques available at NYU and magnetic imaging methods available at U.S. National Labs. This research will be integrated with the training of young scientists in this forefront area of magnetism research. Graduate and undergraduate students involved in this collaboration will gain experience by interactions between academia and industry and through exchanges between NYU and IBM. Their education will be enriched through exposure to a variety of perspectives, expertise and techniques present in an industrial setting. High school students will also participate in this research.Technical Abstract:This NSF-GOALI project brings together leading researchers in nanomagnetism from New York University and IBM with the aim of furthering the understanding of the physics of spin-transfer. Spin-transfer is a mechanism by which a spin-polarized current can reverse the magnetic orientation of a nanomagnet and induce magnetic excitations such as spin-waves. Understanding the nature of spin-transfer induced spin excitations is a very active area of present day research. The proposed research seeks to advance the understanding and application of two types of collective spin excitations that are generated by the spin-transfer interaction: magnetic solitons, which are localized spin excitations excited in nanometer scale electric contacts to magnetic thin films, and superspin currents excited in easy-plane magnetic layers. Fundamental questions regarding the lifetime, dynamics and degree of coherence of magnetic solitons will be addressed experimentally in samples in which soliton dynamics can be controlled with external perturbations (e.g. applied fields and currents). Scanning transmission x-ray microscopy will be used to image the magnetization dynamics to provide direct information on the nature of the current-induced spin excitations. Parallel theoretical work will explore the effects of temperature and other perturbations, as well as the effects of confined geometries, on soliton lifetimes and dynamics, and will explore transitions between nontopological and topological states. Superspin currents will be explored in samples consisting of proximal nanocontacts for the injection and detection of spin-currents. These experiments will aim to demonstrate and evaluate the efficiently of this newly proposed mechanism of spin transport. Graduate and undergraduate students involved in this collaboration will gain experience by interactions between academia and industry and through student exchanges between NYU and IBM. Their education will be enriched through this integrated experimental and theoretical project, as well as the variety of perspectives, expertise and techniques present in an industrial setting. High school students will also be encouraged to participate in this research project.