Scalable Three Terminal Memory Devices based on Silicon-Compatible Antiferromagnetic Materials

反铁磁材料是没有净宏观磁化的磁有序材料。它们提供的特性使它们有望用于高密度，快速和低功耗的非易失性存储器设备：首先，相邻位之间没有位间偶极子相互作用，使得可以将相邻位放置得比铁磁设备更靠近。其次，反铁磁体由于其交换主导的动力学，可能具有皮秒范围内的超快写入时间。第三，基于这些材料的设备将不受磁场干扰，使它们比基于铁磁体的设备更安全。然而，迄今为止，这些器件的实现一直受到与反铁磁材料电相互作用的困难的阻碍，特别是在工业相关材料和纳米尺度下。该项目旨在开发具有完全电读写能力的三端反铁磁存储器件，该器件基于硅兼容反铁磁材料，可以集成到现有的半导体制造工艺中。该项目将产生重大的经济影响，使磁存储器能够满足比目前更广泛的市场，包括动态随机存取存储器和嵌入式静态随机存取存储器。除了经济影响外，该项目还将通过纳入重要的外联和教育活动，产生更广泛的影响。这包括通过西北大学艺术工程跨学科外联项目，通过表演艺术（科学为主题的戏剧和电影放映）向更广泛的公众进行宣传。研究成果也将被整合到PI在西北大学教授的一门新开发的课程中，该课程侧重于磁学和自旋电子学的基础和应用。该提案的智力价值在于三端非易失性存储器件的器件设计、建模、制造和电学特性。该器件将主要基于非共线导电反铁磁材料，该材料可以在硅衬底上沉积（例如，SnMn 3、GaMn 3、IrMn 3和相关化合物）。磁性状态将通过来自相邻重金属的电流感应自旋轨道扭矩来电控制。该项目旨在展示该设备操作的规模缩小到行业相关的钻头直径。该项目还将通过隧道磁阻结构将电写入机制与电读出集成，将Néel矢量修改转化为电阻变化。读取和写入路径的分离允许更高的循环耐久性和用于读取和写入步骤的材料参数的单独优化。热预算，统计变化引起的设备的可变性，以及其他影响的制造工艺对设备特性的影响将进行调查。将充分表征所开发的存储器装置以在写入时间、写入能量、写入错误率（即，切换概率）、读取干扰率和循环耐久性。设备级权衡（例如，在速度和耐久性之间）将被表征并与其他现有的和新兴的存储器技术进行比较。建模将在微磁水平上进行，以帮助器件设计，并在基于物理的紧凑模型水平上进行，以允许在电路设计环境中实施。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Antiferromagnetic materials are magnetically ordered materials without a net macroscopic magnetization. They offer characteristics that make them promising for high-density, fast, and low-power nonvolatile memory devices: Firstly, there is no inter-bit dipole interaction between neighboring bits, making it possible to place adjacent bits closer together than with ferromagnetic devices. Secondly, antiferromagnets can potentially have ultrafast write times in the picosecond range, due to their exchange-dominated dynamics. Thirdly, devices based on these materials would be immune to tampering by magnetic fields, making them more secure than ferromagnet-based devices. However, to date, the realization of these devices has been hindered by the difficulty of electrically interacting with antiferromagnetic materials, particularly in industry-relevant materials and at nanoscale dimensions. This project aims to develop three-terminal antiferromagnetic memory devices with full electrical read and write capability, based on silicon-compatible antiferromagnetic materials that can be integrated in existing semiconductor manufacturing processes. This project will have a significant economic impact by enabling magnetic memories to address broader markets than currently possible, including dynamic random-access memory and embedded static random-access memory. In addition to its economic impact, this project will achieve broader impact through the incorporation of significant outreach and education activities. This includes outreach to the broader public through performance arts (science-themed plays and film screenings) through the Engineering Transdisciplinary Outreach Project in the Arts at Northwestern University. Research results will also be integrated into a newly developed course that the PI is teaching at Northwestern University, which focuses on the fundamentals and applications of magnetism and spintronics.The intellectual merit of this proposal is in the device design, modeling, fabrication, and electrical characterization of three-terminal nonvolatile memory devices. The devices will be primarily based on noncollinear conductive antiferromagnetic materials that can be sputter-deposited on silicon substrates (e.g., SnMn3, GaMn3, IrMn3 and related compounds). The magnetic state will be controlled electrically via current-induced spin-orbit torque from an adjacent heavy metal. The project aims to demonstrate scaling of this device operation down to industry-relevant bit diameters. The project will also integrate the electrical write mechanism with electrical readout via a tunneling magnetoresistance structure, translating the Néel vector modification into an electrical resistance change. The separation of read and write paths allows for higher cycling endurance and separate optimization of material parameters for the read and write steps. Thermal budgets, statistical variations induced by device variability, and other effects of the fabrication process on device characteristics will be investigated. The developed memory devices will be fully characterized to compare their performance to existing ferromagnet-based memory devices in terms of write time, write energy, write error rates (i.e., switching probability), read disturb rates, and cycling endurance. The device-level tradeoffs (e.g., between speed and endurance) will be characterized and compared to other existing and emerging memory technologies. Modeling will be performed both at the micromagnetic level to aid in device design, and at the physics-based compact model level, to allow for implementation into circuit design environments.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.