Spin Transport and Dynamics in Ferromagnet-Semiconductor Structures

本项目将研究铁磁-半导体混合异质结构中自旋输运和动力学的基本物理。本文将制备由自旋注入产生大量非平衡自旋居群的器件，并研究自旋极化梯度对电荷和自旋输运的影响。自旋输运的机制将通过开发新的自旋敏感电探测技术来探索。特别令人感兴趣的是自旋轨道效应和超精细效应，它们既提供了控制电子自旋的新手段，也提供了自旋弛豫的潜在来源。该项目由三个部分组成。首先，将开发允许在亚微米长度尺度上产生偏振梯度的新设备。其次，对自旋动力学敏感的电测量将用于研究GaAs和InxGa1-xAs中金属-绝缘体跃迁附近的自旋和电荷输运耦合。最后，将在纳秒级时间尺度上研究半导体和铁磁体自旋之间的动态耦合。非技术磁性材料，如铁、钴或镍是数据存储技术的基石，也是从汽车到心脏除颤器等广泛应用的传感器的关键组成部分。该项目将探索一类新型系统的基础科学，其中磁性材料（如铁）与半导体相结合。研究生和本科生将接受纳米制造和测量技术方面的培训，以制造和研究基于这些材料的设备。最近的研究表明，电子可以从铁磁性金属转移到半导体中，同时以自旋的形式保留磁性信息，这类似于附着在电子上的小磁铁。这个项目将决定磁性信息如何在半导体内部传输，然后以电子方式读出。将开发出结合极小磁体和薄层半导体的新型电子器件。极小（小于1微米）和快速（小于十亿分之一秒）设备开发的新领域将得到解决。这项研究的结果将在需要将存储和处理能力结合在单个电路元件中的应用中非常有用。

TechnicalThis project will address the fundamental physics of spin transport and dynamics in hybrid ferrromagnet-semiconductor heterostructures. Devices in which large non-equilibrium spin populations are generated by spin injection will be fabricated, and the effects of spin polarization gradients on both charge and spin transport will be investigated. Mechanisms for spin transport will be probed by exploiting new spin-sensitive electrical detection techniques. Of particular interest are spin-orbit and hyperfine effects, which provide both new means for controlling electron spins as well as potential sources of spin relaxation. The project consists of three components. First, new devices will be developed allowing for the generation of polarization gradients on sub-micron length scales. Second, electrical measurements sensitive to spin dynamics will be used to investigate the coupling of spin and charge transport near the metal-insulator transition in GaAs and InxGa1-xAs. Finally, dynamic coupling between spins in the semiconductor and the ferromagnet will be investigated on nanosecond time scales.Non-technicalMagnetic materials such as iron, cobalt or nickel represent a cornerstone of data storage technologies, and they are also a critical component in sensors for a wide range of applications from cars to cardiac defibrillators. This project will explore the fundamental science of a new class of systems in which magnetic materials such as iron are combined with semiconductors. Graduate and undergraduate students will be trained in the nanofabrication and measurement techniques required to fabricate and study devices based on these materials. Recent research has shown that electrons can be transferred from ferromagnetic metals into semiconductors while preserving magnetic information in the form of their spin, which is analogous to a small magnet attached to the electron. This project will determine how magnetic information can be transported inside semiconductors and then read out electronically. New electronic devices combining very small magnets with thin layers of semiconductor will be developed. New frontiers in the development of extremely small (less than one micron) and fast (less than one billionth of a second) devices will be addressed. The output of this research will be useful in applications where storage and processing capabilities need to be combined in a single circuit element.