Spin information propagation in metallic and insulating ferromagnet based devices

自从1988年发现巨磁阻效应以来，自旋电子学的理论和实验都取得了巨大的进展。特别是，许多新的物理概念的产生和检测的自旋积累和自旋电流已被提出和确认。随后提出了一系列合理的基于自旋的器件。然而，除了基于自旋阀和磁隧道结的硬盘驱动器和随机存取存储器的巨大成功之外，其他提出的自旋器件甚至没有希望。从目前的理论和模拟的角度来看，无法转移新的自旋现象，如自旋霍尔电导，自旋泵和自旋电动势，以有前途的设备应用是由于太小的信号固有的这些现象和太难在实际的设备fabrication.Intellectual优点：目前的建议旨在推进自旋电子学领域的调查非平衡自旋波传播在各种外部可控条件。在描述磁化动力学的传统方法中，在电流和磁场的存在下，通过广义Landau-Lifshitz-吉尔伯特方程经典地处理磁化矢量。本文提出的新概念和方程涉及到导电电子和磁化强度的量子性质：电子和磁化强度的激发都是服从非平衡量子分布方程的量子对象。具体而言，传导电子和自旋波都能够在磁介质中传播自旋信息，尽管它们满足不同的量子统计。广义自旋流，包括电子和自旋波的自旋流，将在各种材料和器件中进行研究。其核心目标是寻找基于超越经典磁化传播的量子自旋传播的自旋器件。更广泛的影响：自旋电子学的研究从根本上推进了我们对经典磁化和量子电子输运之间边界的认识。这项研究将把传统的经典磁化模型带到一个全新的领域。自旋波的量子非平衡分布可以产生前所未有的有趣现象。可能的器件概念和提出的原型器件结构是高风险的，但在基于上级自旋的器件方面的潜在突破是可能的。该提案的教育部分包括研究生参与研究，培训和访问研究生和本科生的工业研究实验室，以及PI开发与该研究项目相关的自旋电子学课程和教科书。

Since the discovery of the giant magnetoresistive effect in 1988, tremendous advances in spintronics theory and experiment have been made. In particular, numerous novel physics concepts related to the generation and detection of spin accumulation and spin current have been proposed and confirmed. A wide range of plausible spin-based devices have subsequently been proposed. However, aside from the colossal success of hard disk drives and random access memories which are based on spin valves and magnetic tunnel junctions, other proposed spin devices have not been even remotely promising. From the view point of current theory and simulation, the inability to transfer new spin phenomena such as spin Hall conductance, spin pumping and spin electromotive force to promising device application is attributed to too small signals inherent in these phenomena and too difficulty in practical device fabrication.Intellectual merit:The present proposal aims to advance the spintronics field by investigating non-equilibrium spin-wave propagation in various externally controllable conditions. In the traditional approach of describing magnetization dynamics, the magnetization vector has been treated classically via generalized Landau-Lifshitz-Gilbert equations in the presence of the current and the magnetic field. The new concepts and equations proposed here involve quantum nature of the conduction electrons and magnetization: the excitations of electrons and of magnetization are quantum objects which obey the equation of the non-equilibrium quantum distributions. Specifically, both conduction electrons and spin waves enable to propagate spin information in magnetic media although they satisfy different quantum statistics. The generalized spin current, including the spin current of electrons and of spin waves, will be investigated in various materials and devices. The central goal is to find possible spin devices based on the quantum spin propagation beyond classical magnetization propagation.Broader impact: The spintronics research has fundamentally advanced our knowledge at the boundary between classical magnetization and quantum electron transport. The proposed research would take the traditional classical modeling for the magnetization to a fundamentally new region. The quantum non-equilibrium distribution for spin waves can generate unprecedented interesting phenomena. The possible device concepts and proposed prototype device structures are high risks but a potential breakthrough in superior spin-based devices is a possibility. The educational components of the proposal include strong graduate student participation in research, training, and visiting industrial research laboratories for the graduate and undergraduate students, as well as for PI to develop a spintronics course and textbook related to this research project.