Spin Pumping in Ferromagnet-Semiconductor Heterostructures

铁磁体半导体异质结构中的自旋泵浦

• 批准号: 1708287
• 负责人: Paul Crowell
• 金额: $ 43.28万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708287&HistoricalAwards=false
• 关键词: Spin; Pumping; Ferromagnet; Semiconductor; Heterostructures

Non-Technical Abstract:Magnetic materials such as iron form the basis of storage technologies such as computer hard disks, while semiconductors such as silicon are the foundation of a vast array of microelectronic devices. This project addresses the fundamental question of how these two very different types of materials can be combined to create electronic devices with new capabilities, including the integration of memory and processing functions on a single chip. To help accomplish this, the principal investigator and his team investigate a process in which information is transferred from the magnetic material to the semiconductor using microwaves, which are the types of waves used in applications such as cellphones. The microwaves are used as a "pump" to generate a flow of spin (the carrier of information) from the magnetic material into the semiconductor. The project determines how efficient this process is and how the flow of spin can be detected inside the semiconductor. By using microwaves instead of an ordinary current generated by a battery, the speed of these devices operate can be enhanced. New magnetic materials for transferring spin into the semiconductor are explored, also allowing for more efficient operation at higher temperatures. In addition to advancing a technology that can be used in information processing, the project trains undergraduate and graduate students in techniques for fabricating and measuring this new class of electronic devices.Technical Abstract:Semiconductors provide a unique environment for controlling spin-polarized carriers using electric and magnetic fields, but the transfer of spin from ferromagnetic materials into semiconductors is a significant challenge. This project develops a means to transfer spins directly from a metallic ferromagnet into a semiconductor at microwave frequencies. This approach, known as spin pumping, has been applied effectively to metals, but it has not yet been tested quantitatively in the case of semiconductors. The effort exploits recent advances in the generation and detection of spin-polarized carriers in devices integrating highly-polarized Heusler alloy ferromagnets with III-V semiconductors. These heterostructures are optimized for operation at microwave frequencies, and the spin pumping approach is then compared quantitatively with established spin transport techniques, including non-local spin valve and spin Hall effect measurements. The important parameters governing the spin-pumping mechanism, including the interfacial mixing conductance and spin Hall angle, are to be measured independently. The spin pumping efficiency is enhanced by modifying the ferromagnet-semiconductor interface, allowing for spin injection into systems with strong spin-orbit interaction. The ultimate goal of the program is to demonstrate the conversion of a spin current to a charge current in a two-dimensional electron system that is driven by spin pumping from a ferromagnet. This requires a progression of devices starting in GaAs-based heterostructures and moving towards InAs quantum wells.

非技术摘要：铁等磁性材料构成了计算机硬盘等存储技术的基础，而硅等半导体则是大量微电子设备的基础。 该项目解决了如何将这两种截然不同的材料组合起来以创建具有新功能的电子设备的基本问题，包括在单个芯片上集成存储器和处理功能。 为了帮助实现这一目标，首席研究员和他的团队研究了一种利用微波（手机等应用中使用的波类型）将信息从磁性材料传输到半导体的过程。 微波用作“泵”，产生从磁性材料到半导体的自旋流（信息载体）。 该项目确定了该过程的效率以及如何检测半导体内部的自旋流。 通过使用微波代替电池产生的普通电流，可以提高这些设备的运行速度。 人们探索了用于将自旋转移到半导体中的新磁性材料，也允许在更高温度下更有效地运行。 除了推进可用于信息处理的技术外，该项目还培训本科生和研究生制造和测量此类新型电子器件的技术。 技术摘要：半导体为利用电场和磁场控制自旋极化载流子提供了独特的环境，但自旋从铁磁材料到半导体的转移是一个重大挑战。 该项目开发了一种在微波频率下将自旋直接从金属铁磁体转移到半导体的方法。这种称为自旋泵浦的方法已有效地应用于金属，但尚未在半导体中进行定量测试。这项工作利用了在将高极化赫斯勒合金铁磁体与 III-V 族半导体集成的器件中自旋极化载流子的生成和检测方面的最新进展。这些异质结构针对在微波频率下的操作进行了优化，然后将自旋泵浦方法与已建立的自旋输运技术（包括非局部自旋阀和自旋霍尔效应测量）进行定量比较。 控制自旋泵浦机制的重要参数，包括界面混合电导和自旋霍尔角，需要独立测量。 通过修改铁磁体-半导体界面可以提高自旋泵浦效率，从而允许将自旋注入具有强自旋轨道相互作用的系统。该计划的最终目标是演示在由铁磁体自旋泵浦驱动的二维电子系统中自旋电流到充电电流的转换。 这需要一系列器件从基于 GaAs 的异质结构开始，逐渐转向 InAs 量子阱。

项目成果

Influence of the magnetic proximity effect on spin-orbit torque efficiencies in ferromagnet/platinum bilayers

• DOI: 10.1103/physrevb.97.020403
• 发表时间: 2017-11
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: T. Peterson;A. McFadden;C. Palmstrøm;P. Crowell

Interplay of large two-magnon ferromagnetic resonance linewidths and low Gilbert damping in Heusler thin films

Heusler 薄膜中大二磁振子铁磁共振线宽和低吉尔伯特阻尼的相互作用

• DOI: 10.1103/physrevb.101.134430
• 发表时间: 2020
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Peria, W. K.;Peterson, T. A.;McFadden, A. P.;Qu, T.;Liu, C.;Palmstrøm, C. J.;Crowell, P. A.
• 通讯作者: Crowell, P. A.