Magnetic Skyrmion for Nonvolatile Low-Power Spin-Orbitronics Applications

本提案旨在解决与互补金属氧化物半导体（CMOS）的缩放相关的挑战性问题：功耗和可变性。为了实现这一目标，提出的研究探索了基于磁skyrmions的非易失性、高密度和低功耗室温应用的磁存储器件的可能性。磁基子是一种类似粒子的、拓扑保护的磁畴。作为一种非易失性信息载体，存储器器件中的每个独立的skyrmion由于体积小、驱动电流密度低和额外的拓扑保护，可以实现高密度、低功耗的操作。本研究将建立一种以拓扑保护自旋织构作为信息载体的磁存储器件框架。这种影响将是变革性的，从而使新型磁存储器的构建成为可能。高密度内存将有助于加速大数据和物联网时代的进步。同时，当与CMOS半导体技术集成时，它有可能解决能耗挑战，从而进一步推进技术节点。此外，这一跨学科研究还具有巨大的教育影响，因为自旋轨道耦合工程的新知识将对新生产生新的教育意义。从高中到本科/研究生，以及博士后（包括女性和少数民族）的学生将通过PI参与加州大学洛杉矶分校的高中和新生拓展项目，接触和培训物理科学和工程以及计算机科学这一跨学科和多学科的新兴领域。这些新兴学科的学生培训将提供多样化的人力资本，精通科学方法并具有应用经验。通过加州纳米系统和NSF-ERC纳米多铁系统的转化应用，目前的推广项目进一步扩大了教育影响。虽然skyrmions本质上可以存在于一组所谓的磁材料（B-20）化合物中，但磁性多层或界面中的skyrmions将与现有的磁记录/存储技术更加兼容。因此，本项目重点研究铁磁层/重材料（FM/HM）薄膜系统中skyrmion的产生、操纵和检测。该系统为应用程序提供了最大限度地调整和调优skyrmion属性的可能性。单个宇宙粒子的产生和湮灭将通过实验实现，并进行动态和静态的理论分析。相对论性自旋轨道耦合（SOC）产生的自旋轨道转矩可以通过电流控制对skyrmions的操纵。通过磁隧道结，利用磁阻效应可以检测到每个单独的粒子。单个Skyrmions的单个自旋纹理将通过微磁模拟建模。从这项研究中获得的知识和经验将使信息的电子编码和解码成为可能；在本研究中，使用了常见的低温工艺薄膜材料系统，自动确保了设备与当前的CMOS或磁记录技术完全兼容。该研究具有变革性，因为它调用了许多独特的创新：(1)FM/HM异质结构中的界面Dzyaloshinskii-Moriya相互作用，以创建具有可控尺寸的skyrmion；(2)利用电流诱导的自旋-轨道转矩在调频/调频界面上有效地操纵skyrmion运动；(3)利用高质量的MTJ进行信息编码和检测；(4)纳米结构工程与压控磁各向异性（VCMA）。

This proposal aims to resolve the challenging issues related to the scaling of complementary metal-oxide-semiconductor (CMOS): power dissipation and variability. To achieve this goal, the proposed research explores the possibilities to build magnetic memory devices based on magnetic skyrmions for room-temperature applications featuring in nonvolatile, high density and low-power consumption. A magnetic skyrmion is a particle-like, topologically protected magnetic domain. As a nonvolatile information carrier, each individual skyrmion in a memory device can enable high-density, low-power operations due to the small size, the low driving current density and the extra topological protection. The proposed research will establish a framework for magnetic memory devices using topologically protected spin texture as the information carrier. The impact will be transformative and thus enables the construction of novel magnetic memory. The high-density memory will help accelerate the progress of the big data and internet-of-things era. Meanwhile, when integrated with the CMOS semiconductor technology, it potentially resolves the energy dissipation challenge and thus further advances the technology node. Additionally, this interdisciplinary research also has a vast educational impact, as the new knowledge from the spin orbit coupling engineering will have emerging educational meaning for new students. Students with education level from high school to undergraduate/graduate students, and postdocs (including women and minorities) will be exposed and trained in this inter- and multi-disciplinary and emerging fields of physical science and engineering as well as computer science through PI's participation of the high school and freshman outreach programs at UCLA. The training of students in these emerging disciplines will provide diverse human capital, versed in scientific method and experienced in the applications. The educational impact is further amplified by current outreach programs through the California NanoSystems and the NSF-ERC on Translational Applications of Nanoscale Multiferroic Systems.Although skyrmions can intrinsically exist in a group of so-called helimagnetic materials (B-20) compounds, skyrmions in magnetic multilayers or interfaces will be more compatible with existing magnetic recording/memory technologies. Thus, the proposed project focuses on the study of skyrmion creation, manipulation and detection in ferromagnetic layer/heavy-material (FM/HM) thin-film systems. This system provides the possibility to furthest adjust and tune the skyrmion properties for application purposes. The creation and annihilation of single, individual skyrmions will be experimentally realized and theoretically analyzed dynamically and statically. The manipulation of skyrmions can be controlled by currents via spin-orbit torque coming from the relativistic spin-orbit coupling (SOC). Each individual skyrmion can be detected using magnetoresistance effect via magnetic tunnel junctions. Single spin textures of single Skyrmions will be modeled via micromagnetic simulation. Knowledge and experience learnt from this study will enable electrically encoding and decoding of information; the use of commonly accessible thin film material systems with low-temperature process in this research automatically ensures devices to be fully compatible with current CMOS or magnetic recording technology. The proposed research is transformative since it invokes many unique innovations from (1) interfacial Dzyaloshinskii-Moriya interaction in FM/HM heterostructures to create skyrmion with controllable sizes; (2) effectively manipulation of skyrmion motion by the current-induced spin-orbit torque at the FM/HM interface; (3) the use of high-quality MTJ for information encoding and detection; (4) nanostructure engineering and voltage-controlled magnetic anisotropy (VCMA).