Nanowire Spin-Valves for Antiferromagnet Spintronics

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“新兴的自旋电子学领域已经彻底改变了信息技术，特别是在过去十年中磁记录面密度的爆炸性增长。自旋电子学的核心是允许低磁场应用的自旋阀和允许磁状态的局部电操纵的自旋转移矩（STT）效应。它们实现了许多迷人的基于自旋的电子应用，从快速、可扩展、非易失性和节能的磁性随机存取存储器到基于畴壁的逻辑和可调谐高频STT振荡器。到目前为止，STT效应仅在铁磁体中进行了研究，直到最近提出了基于反铁磁体（AF）的STT效应。该项目旨在研究多层纳米线中的新型AF-STT效应，并建立一种新型的基于纳米线的AF自旋电子学研究的自旋阀。研究的技术优点如下。将通过电化学沉积将自旋阀并入纳米线。纳米线的晶体结构，特别是AF组分的晶体结构，将被优化。明确定义的结构保证了均匀的电流密度，并允许定量测量交换偏置偏移以测量AF-STT。电流密度，方向和温度对AF-STT的影响将在纳米线阵列和单个纳米线中进行研究。磁化反转机制和不可逆电阻跳跃之间的相关性将使用一阶反转曲线方法以及超快动态研究的时间分辨磁光克尔效应。最后，AF界面磁性微结构的修改的直接证据将通过X-射线磁性圆二色性和线性二色性来探测。 这些研究不仅将系统地和最终地证明AF-STT效应，而且还将推进对STT效应的基本理解，并为自旋电子学探索开辟全新的材料和机制。多层自旋阀纳米线也可用作MR传感器和MRAM元件的原型大规模并行阵列。研究的更广泛影响包括技术进步、学生教育和培训以及对公众的宣传。提出的多层自旋阀纳米线AF-STT研究将有深远的技术影响，因为自旋阀和STT是现代自旋电子器件的核心。拟议项目还将对教育和培训产生广泛影响。参与研究的研究生将获得良好的大学和国家实验室研究环境的机会。该项目还将涉及本科生，特别是那些旨在从事教学职业的学生，以及高中生。演讲技巧将在学生培训中得到强调。研究工作将被纳入课程开发，并有助于扩大本科实验室课程和研究生课程。计划开展外联活动，包括积极参与纳米科学非正式科学教育（NISE）网络。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."The emerging field of spintronics has already revolutionized information technology, particularly in the explosive growth of the magnetic recording areal density over the past decade. At the heart of spintronics are spin-valves that permits low magnetic field applications and a spin-transfer torque (STT) effect that allows local electrical manipulation of magnetic states. They enable a host of fascinating spin-based electronics applications, from fast, scalable, non-volatile and energy-efficient magnetic random access memory, to domain wall based logic and tunable high frequency STT oscillators. The STT effect has so far been exclusively studied in ferromagnets, until the recent theoretical proposals of antiferromagnet (AF) based STT effect. The PI aims at investigating the novel AF-STT effect in multilayered nanowires and building a novel type of nanowire based spin-valves for AF spintronics explorations. The technical merits of the research are as follows. Spin-valves will be incorporated into nanowires by electrochemical deposition. Crystal structures of the nanowires, particularly those of the AF components, will be optimized. The well-defined structure guarantees uniform current density and allows quantitative measures of the exchange bias shift to gauge the AF-STT. The effect of current density, direction, and temperature on the AF-STT will be investigated, in both arrays of nanowires and a single nanowire. Correlation between magnetization reversal mechanisms and irreversible resistance jumps will be examined using a first order reversal curve method as well as ultrafast dynamic study by time-resolved magneto-optical Kerr effect. Finally, direct evidence on the modification of the AF interfacial magnetic microstructure will be probed by x-ray magnetic circular and linear dichroism. These studies will not only systematically and conclusively demonstrate the AF-STT effect, but also advance the basic understanding of the STT effect and open up whole new classes of materials and mechanisms for spintronics explorations. The multilayered spin-valve nanowires also serve as prototype massively parallel arrays of MR sensors and MRAM elements. The broader impacts of the research include technological advances, student education and training, and outreach to the general public. The proposed multilayered spin-valve nanowires for AF-STT studies will have far reaching technological impacts since both spin-valve and STT are at the heart of modern spintronic devices. The proposed project will also have broad impacts on education and training. Graduate students involved will receive excellent exposure to university and national laboratory research environment. This project will also involve undergraduate students, especially those aiming at a teaching career, as well as high school students. Presentation skills will be emphasized in student training. The research efforts will be integrated into curriculum development and help to expand an undergraduate lab course and a graduate course. Outreach activities including active participation in the Nanoscience Informal Science Education (NISE) network are planned.