Non-volatile magnetic memory devices based on field-free spin-orbit torque switching of perpendicularly polarized magnets.

基于垂直极化磁体的无场自旋轨道扭矩切换的非易失性磁存储器件。

• 批准号: 2208057
• 负责人: Simranjeet Singh
• 金额: $ 34.49万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2208057&HistoricalAwards=false
• 关键词: Non; volatile; magnetic; memory; devices

Exploitation of spin degree of freedom in solid state systems is key to realizing ultrafast, energy efficient, and densely packed magnetic data storage devices. In these magnetic memory devices, the information is encoded in the magnetization direction of a bistable ferromagnetic thin film layer. To achieve thermally stable and closely packed magnetic bits, a perpendicularly magnetized ferromagnetic layer is preferred. Spin orbit torques, generated by applying a charge current to an adjacent spin source material, has emerged as an efficient means to manipulate or switch the perpendicularly magnetized ferromagnetic layer. However, an external magnetic field is required to achieve deterministic spin orbit torque switching of a perpendicularly magnetized ferromagnetic layer because the charge-current induced spin current in conventional spin-source materials is polarized in the film plane due to the crystal symmetry. This fundamental limitation in conventional spin-source materials has prevented the use of spin orbit torque to achieve field-free deterministic switching of ferromagnets with perpendicular magnetic anisotropy. To overcome this longstanding hurdle in the field of spintronics, this research program proposes to explore low-symmetry crystal structure and topological electronic structure in a special class of materials, namely Weyl semimetals, to demonstrate field-free deterministic magnetization switching of variety of perpendicularly magnetized ferromagnets. A successful outcome of this research program will lead to next generation energy efficient magnetic memory and spin-logic devices. This research program will support the education and training of a graduate student and undergraduate students. Through proposed research activities, the graduate student and undergraduate students will be trained in experimental techniques and skill sets for spin orbit torques for nonvolatile magnetic memory devices. Educational outreach activities and events will be planned to kindle scientific interest and provide interactions and mentorship for middle school and high school students, especially those belonging to underrepresented minorities in southwestern Pennsylvania. Moreover, hands-on experimental demos to explain spin and magnetism-related phenomena will be developed for outreach activities.Utilization of topology and crystal-symmetry in emergent quantum materials, to obtain large current induced spin orbit torques for an energy efficient and field-free manipulation of the magnetization in FM materials, is promising for spintronic device applications. In this context, Weyl semimetals provide a distinct opportunity to obtain highly efficient and unconventional charge to spin conversion owing to strong spin-orbit coupling, symmetry breaking, and topology-based phenomena. The goal of this research program is to demonstrate field-free operation of spin orbit torque-based prototype magnetic memory devices that exploit the interplay of low-symmetry crystal structure and topological electronic structure in Weyl semimetal candidate materials to generate spin current with out-of-plane spin polarization. The main research objectives of this program are to use electric field induced out-of-plane oriented spin current in Weyl semimetals to demonstrate field-free magnetization manipulation in three different classes of ferromagnets with perpendicular magnetic anisotropy, namely: (1) van der Waals based semi-metallic ferromagnets; (2) van der Waals based semiconducting ferromagnets; and (3) a ferromagnetic insulator. In proposed devices, integrated electrostatic gates will be used to tune the charge carrier density in Weyl semimetal thin films, to control magnetism in semiconducting ferromagnets for enhanced spin orbit torque-based device functionalities, and to probe electric-field dependent switching phase diagram to map out the optimal parameter space for low-energy spin orbit torque switching for magnetic memory applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

固态系统中自旋程度的开发是实现超快，能源效率和密集的磁性数据存储设备的关键。在这些磁性记忆设备中，信息是在双磁性薄膜层的磁化方向上编码的。为了获得热稳定且紧密堆积的磁位，首选垂直磁化的铁磁层。通过将电荷电流应用于相邻的自旋源物质而产生的旋转轨道扭矩已成为一种有效的手段来操纵或切换垂直磁化的铁磁层。但是，需要外部磁场来实现垂直磁化铁磁层的确定性旋转轨道扭矩切换，因为由于晶体对称性，在传统的自旋源材料中电荷电流诱导的旋转电流在膜平面上极化。常规自旋源材料中的这种基本限制阻止了使用自旋轨道扭矩实现具有垂直磁各向异性的铁磁体的无现场确定性切换。为了克服SpinTronics领域的这一长期障碍，该研究计划提议在特殊类别的材料（即Weyl Semimetals）中探索低对称性的晶体结构和拓扑电子结构，以证明无现场的确定性确定性磁力化切换了各种垂直磁性磁性磁力强度的磁力。该研究计划的成功结果将导致下一代节能的磁记忆和自旋逻辑设备。该研究计划将支持研究生和本科生的教育和培训。通过拟议的研究活动，将对研究生和本科生进行实验技术和技能培训，用于用于非挥发性磁性记忆设备的旋转轨道扭矩。教育外展活动和活动将计划在宾夕法尼亚州西南部的中学和高中学生，尤其是那些属于代表性不足的少数群体的学生，为中学和高中生提供互动和指导。此外，将开发动手实验性演示来解释与磁性和磁性相关的现象，以进行外展活动。在紧急量子材料中拓扑和晶体对称性的利用，以获得大型电流诱导的旋转旋转轨道扭矩，以进行能源有效且无野外的磁力操纵，从而在FM材料中进行磁化材料的无效操纵，可用于旋转设备进行启动式旋转设备。在这种情况下，Weyl半法定为获得高效和非常规的电荷提供了一个独特的机会，以通过强旋转轨道耦合，对称性断裂和基于拓扑的现象，从而获得高效和非常规的电荷。该研究计划的目的是证明基于旋转轨道扭矩的原型磁性记忆设备的无现场操作，以利用魏尔半分化候选材料中低对称性晶体结构和拓扑电子结构的相互作用，以产生与平面外旋转极化的旋转电流。该程序的主要研究目标是使用电场诱导的Weyl Semimetals中面向脱落的旋转电流，以证明三种不同类别的具有垂直磁各向异性的铁磁体中的无现场磁化操纵，即：（1）van der waals基于半金属金属的费用磁铁； （2）基于范德华的半导体铁磁体； （3）铁磁绝缘子。在拟议的设备中，将使用集成的静电门来调整Weyl半光薄膜中的电荷载体密度，以控制半导体的半导体铁电磁体中的磁性，以增强基于旋转轨道扭矩的设备功能，并用于探测电场依赖性相位图以绘制出较低的旋转旋转型旋转型旋转的旋转型号，以绘制出磁性旋转的空间。法定任务，并被认为是值得通过基金会的智力优点和更广泛影响的审查标准来评估的值得支持的。