FRG: NIRT: Quantum Spin Dynamics in Molecular Nanomagnets

****非技术摘要****该奖项来自于一份响应纳米尺度科学与工程计划的提案，NSF 04-043，类别NIRT。它支持一项跨学科的研究工作，将研究化学合成磁性纳米结构的量子动力学。磁性设备小型化到这种尺寸对磁性信息处理的进步至关重要，这是美国的一个重要产业。用于制造磁性纳米结构的传统技术存在严重的局限性。由于这个原因，人们对化学合成越来越感兴趣，化学合成提供了一种自下而上或基于分子的方法来组装磁性纳米结构——通常是磁性结构的原子尺度控制。本项目将重点研究磁化动力学以及纳米磁体的环境如何影响这些动力学。对于大型磁体，这种耦合导致能量耗散或磁摩擦。对于磁性纳米结构来说，环境也会导致量子信息的丢失，这被称为退相干。本项目的一个重要目标是了解纳米磁体中能量耗散和退相干的微观机制，并制定综合策略来减轻某些环境影响，如退相干。磁性纳米结构的化学合成将与先进的磁测量技术相结合，包括高速高灵敏度磁强计、磁共振和中子散射。该项目将为本科生、研究生和博士后科学家提供最高质量的跨学科研究培训。学生将接受尖端化学合成和磁测量技术的培训。材料研究部和化学部为本项目提供支持。****技术摘要****该奖项来自于一项响应纳米尺度科学与工程计划的提案，NSF 04-043，类别NIRT。它支持一项跨学科的研究工作，将使用自下而上或基于分子的方法来研究纳米级单分子磁体（SMMs）的量子自旋动力学。这是一种利用溶液法化学合成磁性纳米结构的强大方法。了解纳米磁体的动力学对技术应用非常重要。特别有趣的是，目前人们对自旋和它们的环境之间的耦合如何影响它们的动力学知之甚少。在经典磁学中，这种耦合导致磁化进动的耗散和阻尼。在量子情况下，与环境的相互作用限制了自旋相干时间并导致量子信息的丢失。本研究项目将研究：量子磁化动力学；能量和角动量松弛；以及纳米磁铁的自旋激发。一个重要的目标是进一步了解纳米磁体的耗散和退相干的微观机制，并制定综合策略来减轻某些环境影响，如退相干。将采用以下实验技术：脉冲EPR，时间分辨和高灵敏度磁强计，核磁共振和非弹性中子散射。通过与橡树岭国家实验室（ORNL）的合作，该团队可以使用后一种技术。该计划将为本科生、研究生和博士后科学家提供最高质量的跨学科研究培训，其中包括新的化学合成方法和先进的磁测量技术的培训。材料研究部和化学部为本项目提供支持。

****NON-TECHNICAL ABSTRACT****This award results from a proposal received in response to Nanoscale Science and Engineering initiative, NSF 04-043, category NIRT. It supports an interdisciplinary research effort that will investigate the quantum dynamics of chemically synthesized magnetic nanostructures. The miniaturization of magnetic devices to this size is critical to advances in magnetic information processing, which is an important industry in the United States. Conventional techniques used to fabricate magnetic nanostructures have serious limitations. For this reason, there is a growing interest in chemical syntheses that provide a bottom-up or molecule-based approach to the assembly of magnetic nanostructures--often, with atomic scale control of magnetic structure. This project will focus on the magnetization dynamics and how the environment of the nanomagnet affects these dynamics. For a large magnet, this coupling leads to energy dissipation or magnetic friction. For magnetic nanostructures the environment also leads to the loss of quantum information, known as decoherence. An important aim of this project is to understand the microscopic mechanisms of energy dissipation and decoherence in nanomagnets, and to develop synthetic strategies to mitigate certain environmental effects, such as decoherence. Chemical synthesis of magnetic nanostructures will be combined with advanced magnetic measurement techniques, which include high-speed high-sensitivity magnetometry, magnetic resonance and neutron scattering. This program will provide the highest quality interdisciplinary research training to a diverse group of undergraduate students, graduate students and post-doctoral scientists. Students will be trained in cutting edge chemical synthesis and magnetic measurement techniques. The Division of Materials Research and the Division of Chemistry provide support for this project.****TECHNICAL ABSTRACT****This award results from a proposal received in response to Nanoscale Science and Engineering initiative, NSF 04-043, category NIRT. It supports an interdisciplinary research effort that will investigate the quantum spin dynamics of nanometer-sized single-molecule magnets (SMMs) using a bottom-up or molecule-based approach. This is a powerful approach in which magnetic nanostructures are synthesized chemically using solution methods. An understanding of the dynamics of nanomagnets is important to technological applications. Of particular interest, and very poorly understood at present, is how the coupling between spins and their environment affect their dynamics. In classical magnetism this coupling leads to dissipation and damping of the magnetization precession. In the quantum case, interaction with the environment limits the spin coherence time and leads to the loss of quantum information. This research program will study: quantum magnetization dynamics; energy and angular momentum relaxation; and spin-excitations in nanomagnets. An important aim is to further understand the microscopic mechanisms of dissipation and decoherence in nanomagnets, and to develop synthetic strategies to mitigate certain environmental effects, such as decoherence. The following experimental techniques will be employed, pulsed EPR, time-resolved and high-sensitivity magnetometry, NMR and inelastic neutron scattering. The latter technique is available to this team through a partnership with Oak Ridge National Lab (ORNL). This program will provide the highest quality interdisciplinary research training to a diverse group of undergraduate, graduate and post-doctoral scientists, which will include training in new chemical synthesis methods and advanced magnetic measurement techniques. The Division of Materials Research and the Division of Chemistry provide support for this project.