ERI: Compositionally modulated ferrimagnets for spin-orbitronic devices

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。铁磁薄膜显示出独特的性能，可以创造新的低功耗，高速和高密度磁性器件。然而，无序可以通过改变薄膜性质来显著影响器件操作。该项目的目标是提供一种特定类型的无序的作用的理解，常见的各种亚铁磁材料-成分不均匀性-在确定的属性，使他们成为下一代磁性器件的理想选择。这项研究将为通过受控生长过程优化未来技术的这些效应提供框架，从而简化器件架构并提高性能。该研究还将产生广泛的教育影响，包括支持一名来自工程和物理领域代表性不足的毕业生，以及让本科生和当地高中生接触磁性材料的高级研究。参与这项研究的学生将有机会与布鲁克海文国家实验室的科学家合作，并获得成像经验和纳米纤维的经验。PI在孟菲斯大学的推广计划中的持续参与扩大了教育影响。TechnicalCurrent基于铁磁材料的自旋电子技术，包括存储器和逻辑器件，通常会导致与能耗，设备可扩展性和稳定性以及速度相关的限制。克服这些限制的一个有前途的方法是亚铁磁自旋电子学的发展，它承诺的优点，高速和低功耗操作常见的反铁磁材料，同时保持简单的生长方法和设备读出常见的过渡金属基铁磁体。这项研究将进一步了解组成调制对Dzyaloshinskiii-Moriya相互作用（Dzyaloshinskii-Moriya Interaction）的自旋轨道现象和过渡金属-稀土亚铁磁体中的自旋轨道扭矩的作用，这是开发高速，低功率器件的关键。该研究将通过以下方式解决这一问题：（1）通过控制溅射沉积和系统测量铁磁和自旋轨道有效场，提高我们对成分调制如何允许在铁磁单层中产生大的自旋轨道效应的理解，（2）定量地将薄膜厚度的磁性变化与Co基铁磁中的大自旋轨道效应联系起来，以及（3）提供一种框架，以基于上述组分调制来开发单层、有效的自旋-轨道扭矩器件，从而简化它们的制造要求并提高性能。为了实现这些目标，在成分变化的亚铁磁膜的磁和自旋轨道转矩的强度将检查由克尔显微镜测量的静态和动态域配置和测量的非对称畴壁运动驱动的磁场和电流。电子显微镜，体磁，和X射线技术将被用来链接这些属性直接组成的非均匀性。对标准霍尔交叉和纳米线几何形状进行的开关过程的电测量和直接成像将允许成分调制与器件性能直接相关，包括开关效率和有效磁场的强度，并为更快，更有效的磁存储器，逻辑，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Ferrimagnetic thin films display unique properties which may enable the creation of new low power, high speed, and high-density magnetic devices. However, disorder can significantly influence device operation by modifying thin film properties. The goal of this project is to provide an understanding of the role that a specific type of disorder common to a wide range of ferrimagnetic materials - compositional nonuniformity - plays in determining the properties that make them ideal for next-generation magnetic devices. This research will provide the framework for the optimization of these effects for future technologies through controlled growth processes, and in turn, simplifying device architectures and improving performance. The research will also have a wide educational impact, including supporting one graduate from an underrepresented group in Engineering and Physics as well as exposing undergraduate and local high school students to advanced research in magnetic materials. The students participating in this research will have the opportunity to collaborate with scientists at Brookhaven National Laboratory and gain hands on imaging experience as well as experience in nanofabrication. The educational impact is amplified by the PI’s ongoing participation in outreach programs at the University of Memphis.TechnicalCurrent spintronic technologies based on ferromagnetic materials, including memory and logic devices, often incur limitations related to energy consumption, device scalability and stability, as well as speed. One promising approach to overcoming these limits is the development of ferrimagnetic spintronics, which promises the advantages of high speed and low power operation common to antiferromagnetic materials while maintaining the straightforward growth methods and device readout of common transition metal based ferromagnets. This research will further the understanding of the role of compositional modulation on the spin-orbit phenomena of the Dzyaloshinskii-Moriya Interaction (DMI) and spin-orbit torques in transition metal-rare earth ferrimagnets, key to developing high speed, low power devices. The research will address this by (1) improving our understanding of how compositional modulation allows for the generation of large spin-orbit effects in ferrimagnetic single layers through controlled sputter deposition and systematic measurements of DMI and spin-orbit effective fields, (2) quantitatively linking the variation in magnetic properties through the film thickness to the large DMI in Co-based ferrimagnets, and (3) providing a framework to develop single layer, efficient spin-orbit torque devices based on the aforementioned compositional modulation, thereby simplifying their fabrication requirements and improving performance. To achieve these goals, the strength of DMI and spin-orbit torques in compositionally varied ferrimagnetic films will be examined by Kerr microscopy measurements of static and dynamic domain configurations and measurements of asymmetric domain wall motion driven by magnetic fields and electrical currents. Electron microscopy, bulk magnetometry, and X-ray techniques will be used link these properties directly to composition non-uniformities. Electrical measurements and direct imaging of switching processes taken for standard hall cross and nanowire geometries will allow the compositional modulation to be directly linked to device performance, including switching efficiencies and the strength of effective magnetic fields, and pave the way for faster, more efficient magnetic memory, logic, and signal processing devices.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.