EAGER-Generation of Perpendicularly Polarized Spin Current from the Spin-Orbit Effects in Ferromagnetic Thin Film Structures for Memory Applications

存储器应用中的铁磁薄膜结构中的自旋轨道效应急切地产生垂直极化的自旋电流

• 批准号: 1738679
• 负责人: Xin Fan
• 金额: $ 7.95万
• 依托单位: University of Denver
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2018-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1738679&HistoricalAwards=false
• 关键词: EAGER; Generation; Perpendicularly; Polarized; Spin

To accommodate the ever-increasing demand of computational power, there has been a great effort in searching for new types of memories that are fast and energy-efficient. Magnetic random access memory, which uses magnetism to store information and electricity to read/write information, is a potential candidate as the new generation of memory because magnetism is intrinsically non-volatile and switches fast. The main technical challenge is to reduce the amount of energy it takes to switch the magnetization in the writing process of the magnetic random access memory. This project aims to explore an efficient way to switch the magnetization by using a spin current, i.e. a flow of electron spins, with a specially engineered spin orientation. This work will provide transformative information on how to generate perpendicular spins from magnetic structures, which will significantly lower the power consumption in magnetic random access memories with perpendicular magnetizations. The outcome from this research will lead to a significant advance in data storage and information technologies. The spin-orbit effects have been demonstrated to be a promising way to convert an electric current into a spin current that can efficiently switch a magnetization. However, thus far the spin currents generated by the spin-orbit effects are constrained by thin film geometries and therefore are only polarized in-plane. It is inefficient to use an in-plane polarized spin current to switch a perpendicular magnetization, which is technically attractive in the application of memories due to their scalability and thermal stability. In this proposal, the investigator plan to explore the generation of a perpendicularly polarized spin current using the spin-orbit effects in ferromagnetic structures, which is based on the hypothesis that the ferromagnetism provides an additional control on the spin orientation. Two complementary structures will be investigated: the spin filtering, where the spin polarization is aligned with the magnetization, and spin rotation, where the spin polarization is rotated about the magnetization. This project leverages on unique expertise in detecting the spin torque on magnetization using the sensitive magneto-optic-Kerr-effect magnetometry and ferromagnetic resonance-based magnetometry. The specific tasks in the project are (1) quantifying the efficiency to generate perpendicularly polarized spin current in the two ferromagnetic structures and (2) designing efficient device for switching magnetization with a fast switching time. This study will also provide important insights in the comprehensive spin-orbit effects from magnetic structures.

为了满足计算能力的不断增长的需求，在寻找快速和节能的新记忆方面付出了巨大的努力。使用磁性来存储信息和电力以读/写入信息的磁随机访问记忆是新一代记忆的潜在候选者，因为磁力本质上是非挥发性的，并且很快就切换了。主要的技术挑战是减少在磁随机存储器的写作过程中切换磁化所需的能量量。该项目旨在探索一种使用自旋电流（即具有特殊设计的旋转方向的电子旋转流动）来切换磁化的有效方法。这项工作将提供有关如何从磁性结构中生成垂直自旋的变革性信息，这将大大降低具有垂直磁化的磁随机访问记忆中的功耗。这项研究的结果将导致数据存储和信息技术的重大进步。自旋轨道效应已被证明是将电流转换为可以有效切换磁化的自旋电流的一种有希望的方法。但是，到目前为止，由自旋轨道效应产生的自旋电流受薄膜几何形状的约束，因此仅是偏振面内的。使用平面偏光旋转电流来切换垂直磁化的效率低下，由于其可扩展性和热稳定性，在记忆的应用中，在技术上具有吸引力。在该提案中，研究者计划使用铁磁性结构中的自旋轨道效应探索垂直极化的自旋电流的产生，该旋转轨道效应基于以下假设：铁磁性为自旋方向提供了额外的控制。将研究两个互补结构：自旋滤波，其中自旋极化与磁化强度和自旋旋转对齐，其中自旋极化围绕磁化而旋转。该项目利用了使用敏感的磁磁 - 凯尔效应磁力测定法和基于铁磁共振的磁力测定法检测磁化上的自旋扭矩的独特专业知识。项目中的特定任务是（1）量化效率，以在两个铁磁结构中生成垂直极化的自旋电流，以及（2）设计有效的设备，以快速切换时间进行切换磁化。这项研究还将为磁性结构的综合自旋轨道效应提供重要的见解。

项目成果

Spin–Orbit Torques in Metallic Magnetic Multilayers: Challenges and New Opportunities

• DOI: 10.1142/s2010324717400136
• 发表时间: 2017-10
• 作者: Tao Wang;J. Xiao;X. Fan

Free-layer-thickness-dependence of the spin galvanic effect with spin rotation symmetry

• DOI: 10.1063/1.5048012
• 发表时间: 2018-09-17
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Aljuaid, Wafa S.;Allen, Shane R.;Fan, Xin
• 通讯作者: Fan, Xin