Antiferromagnet-based Ultrafast Magnetic Memory Devices

与现有的计算机存储器相比，基于磁性材料的存储器具有功耗低、可扩展性好等优点。此外，在没有电源的情况下，信息被保留在磁存储器中，为新的计算方案提供了可能性。然而，现有的磁存储器件的工作速度相对较低，这极大地限制了其应用。在这项提议中，将开发具有超快写入速度(1纳秒)的磁存储器件，这可能会给存储和数据存储行业带来革命性的变化。实现磁动力学的超快控制也有助于加深对磁性材料性质的认识。除了这些广泛的科学影响，该项目还为学生提供了独特的跨学科培训机会。这项研究计划与教育使命相结合，包括激发K-12学生对科学和工程的职业兴趣；为本科生提供前沿研究机会；通过课程开发和跨学科合作为学生未来的职业生涯做好准备。为了实现超快磁记忆，该计划试图利用自旋电子器件制造技术的快速发展和新磁性材料的最新进展。特别是，为了实现高速度和高存储密度的磁存储，将研究反铁磁体。与常规铁磁体相比，反铁磁体由于具有较高的磁共振频率，具有超快的动力学特性。然而，到目前为止，反铁磁体缺乏有效的控制和检测机制，这给反铁磁体在磁存储器件中的实际实现带来了挑战。在这个方案中，PI聚焦于由反铁磁体制成的具有内部破缺反转对称性的自旋电子器件，其中两个亚晶格的不等价性允许产生交错的自旋轨道扭矩，并为磁探测和操纵提供了可能性。所提出的实验工作的目标包括定量确定写入效率以及探索和优化反铁磁体的读取机制。具体地说，提出了一种独特的测量反铁磁自旋轨道扭矩的方案，通过该方案将揭示和量化反铁磁开关的潜在机制。此外，还将评估反铁磁器件的开关速度，并通过反铁磁磁畴移动实验确定影响高效磁开关的限制因素。最后，通过对隧道各向异性磁阻的研究，可以获得较高的开关比，从而为反铁磁器件提供一种有效的读出机制。总体而言，拟议的研究活动不仅将有助于实现具有快速访问时间和高密度的实用反铁磁磁存储器件，还将增进对反铁磁体中电流感应动力学的理解，并扩大对反铁磁体耦合系统中自旋电荷相互作用的认识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Compared with existing computer memories, memories based on magnetic materials have advantages of lower power consumption and better scalability. Moreover, information is retained in magnetic memories in the absence of power supply, providing possibilities of new computing schemes. However, existing magnetic memory devices have relatively low operating speed, which greatly limits their application. In this proposal, magnetic memory devices with ultrafast writing speed (1 nanosecond) will be developed, which can potentially bring in revolutionary changes in memory and data storage industry. The realization of the ultrafast control of magnetic dynamics could also advance understanding on the properties of magnetic materials. In addition to these broad scientific impacts, this project also provides students with unique transdisciplinary training opportunities. This research project is proposed to be integrated with the educational missions, including inspiring career interest of K-12 students in science and engineering; providing undergraduate students with cutting-edge research opportunities; and preparing students for future careers through curriculum development and interdisciplinary collaboration.To realize ultrafast magnetic memories, this proposal tries to leverage the fast development of fabrication techniques on spintronic devices with the recent advancement in new magnetic materials. Particularly, antiferromagnet will be studied for realizing magnetic memories with superior speed and high storage density. Compared with regular ferromagnet, antiferromagnet has ultrafast dynamics due to the high magnetic resonance frequency. However so far the lack of efficient control and detection mechanisms in antiferromagnet has made it challenging for practical implementations of antiferromagnet in magnetic memory devices. In this proposal, the PI focuses on spintronic devices made from antiferromagnet with internally broken inversion symmetry, where the inequality of the two sub-lattices allows the generation of staggered spin orbit torque and provides the possibility for magnetic probing and manipulation. The goals of the proposed experimental efforts include quantitatively determining the writing efficiency as well as exploring and optimizing the reading mechanisms of antiferromagnet. Specifically, a unique scheme for measuring antiferromagnet spin orbit torque is proposed, through which the underlying mechanisms for antiferromagnet switching will be revealed and quantified. Moreover, the switching speed of antiferromagnet devices will also be evaluated and the limiting factors on efficient magnetic switching will be determined through the antiferromagnet domain movement experiment. Finally, a high ON/OFF ratio will be pursued through the study of tunneling anisotropy magnetoresistance, which can lead to an efficient reading mechanism for antiferromagnet devices. In overall, the proposed research activities will not only facilitate the realization of practical antiferromagnet magnetic memory devices with fast accessing time and high density, but also enhance understanding on the current induced dynamics in antiferromagnet and widen awareness of the spin charge interaction in antiferromagnetically coupled systems.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.