THEORY OF NANOMAGNETS

技术概述：该奖项支持许多自旋与声子相互作用的量子动力学的理论研究和教育，主要集中在分子纳米磁体的应用上。正在研究的新方向包括磁雪崩理论，旋转感应磁，以及自旋-声子耦合引起的远程自旋-自旋相关的发生。改进磁雪崩理论的动机是需要理解在分子磁体晶体中观察到的磁爆燃现象。研究了磁焰的引燃机理和随后的传播机理。此外，另一种基于朗道-齐纳波传播的理论模型，使用解析和数值方法与该理论进行比较。研究了磁爆是由晶格变形耦合的自旋非线性动力学驱动的可能性。此外，研究人员正在开发一种理论方法，以解决在磁性纳米颗粒中观察量子巴内特效应的可能性。这个理论考虑了自由粒子的磁矩与机械旋转的耦合动力学。自旋与高频大振幅声波的相互作用将被研究，重点是动态自旋-旋转耦合。本研究解决了在分子磁体晶体中直接观察自旋-旋转耦合的可能。由于弱耦合自旋与声子相互作用的集合的集体行为正在被研究，以确定相干声子在提供自旋之间的远程相关性方面所起的作用。本研究将结合声子瓶颈、非辐射自旋声子态、自旋声子弛豫的相干放大等在分子磁体中的应用进行研究。研究了自旋晶格弛豫与磁体尺寸的关系。研究生和本科生以及高中生将积极参与本研究。这个项目涉及国际合作。该奖项支持理论研究和教育，旨在对纳米尺度上的磁性有基本的了解，并发现涉及纳米磁铁的新现象。随着材料接近纳米尺度，除了提高对经典物理分解的基本科学理解外，分子磁性材料和其他纳米级磁性颗粒有望对广泛的技术产生积极影响。例子包括磁共振成像技术、磁记录和更新颖的信息技术，如自旋电子学，它试图利用电子的磁性以及它们在新设备和量子计算中的电荷。当宏观材料拉伸、弯曲和扭曲时，磁性粒子与邻近粒子的相互作用方式对这些纳米级粒子的性能和操作环境有很大影响。解释这些相互作用的理论与发现由于这些相互作用而产生的潜在有用效应是同步发展的。基于这些效应的未来可能的技术进步包括激光的声学模拟，光束旋转引起的纳米级磁效应以及称为磁爆燃的特征。磁爆燃是点火和随后火焰蔓延的磁模拟。然而，在分子磁性材料中，这一过程是可逆的，这为我们以一种新的方式扩大对燃烧的理解提供了潜力。研究生和本科生以及高中生将积极参与本研究。这个项目涉及国际合作。

TECHNICAL SUMMARY:This award supports theoretical research and education on quantum dynamics of many spins interacting with phonons and concentrates primarily on applications to molecular nanomagnets. New directions under investigation include theories of magnetic avalanches, rotation-induced magnetism, and the occurrence of long-range spin-spin correlations due to spin-phonon coupling. The improved theory for magnetic avalanches is motivated by the need for understanding the phenomenon of magnetic deflagration observed in crystals of molecular magnets. Mechanisms initiating ignition and subsequent propagation of the magnetic flame are investigated. In addition an alternative theoretical model, based upon a propagating Landau-Zener wave, using analytical and numerical methods is being compared to this theory. The possibility that magnetic detonation is driven by non-linear dynamics of spins coupled with lattice deformations is being investigated. In addition, a theoretical method that addresses the possibility of observing the quantum Barnett effect in magnetic nanoparticles is being developed. This theory considers the coupled dynamics of a magnetic moment of a free particle with the mechanical rotations. The Interaction of spins with high-frequency large-amplitude sound waves will be investigated with an emphasis on dynamical spin-rotation coupling. This research addresses the possible direct observation of spin-rotation coupling in crystals of molecular magnets.Collective behavior due to an ensemble of weakly coupled spins interacting with phonons is a being studied to determine the role that coherent phonons play in providing long-range correlations between the spins. This study connects with the phonon bottleneck, non-radiative spin-phonon states, and coherent amplification of spin phonon relaxation will be studied in application to molecular magnets. The dependence of the spin-lattice relaxation on the size of the magnet will be investigated.Graduate and undergraduate students, as well as high school students will be actively involved in this research. This project involves international collaborations.NON TECHNICAL SUMMARYThis award supports theoretical research and education aimed at a fudamental understanding of magnetism on the nanoscale and the discovery of new phenomena involving nanomagnets. In addition to improving fundamental scientific understanding of the breakdown of classical physics as materials approach the nanoscale size regime, molecular magnetic materials and other nanoscale magnetic particles are expected to positively impact a broad range of technologies. Examples include magnetic resonance imaging technologies, magnetic recording and more novel information technologies such as spintronics, which seeks to exploit the magnetic properties of electrons as well as their charge in new devices and quantum computing. The performance and operating environment of these nanoscale particles is strongly influenced by the way the magnetic particles interact with neighboring particles as the macroscopic material stretches, bends and distorts. Theories to account for these interactions are being developed in parallel with the discovery of potentially useful effects that arise because of these interactions. Possible future technological advances based on these effects include an acoustic analog of the laser, beam rotation induced magnetic effects at the nanoscale and a feature known as magnetic deflagration. Magnetic deflagration is the magnetism analog of the ignition and subsequent spread of flames. However in molecular-magnetic materials the process is reversible which provides the potential for expanding our understanding of combustion in a novel way.Graduate and undergraduate students, as well as high school students will be actively involved in this research. This project involves international collaborations.