CAREER:Toward ultra-low energy switching in spintronic devices

职业：自旋电子器件中的超低能量开关

• 批准号: 1554011
• 负责人: Weigang Wang
• 金额: $ 50万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-02-01 至 2023-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1554011&HistoricalAwards=false
• 关键词: CAREER; Toward; ultra; low; energy

Spintronics makes explicit use of spin, an inherent quantum-mechanical property of electrons, to achieve novel functionalities. A unique advantage of spintronic devices is their nonvolatility: the information they store in spin is retained and remembered even after power is removed from the devices. Nonvolatility is particularly important for the nascent generation of digital devices in which transistor dimensions will be reduced to only a few nanometers. At this nanoscale the power consumption of traditional complementary metal-oxide semiconductor (CMOS) transistors will be dominated by leakage current; whereas, for spintronic structures such energy waste can be completely eliminated. An important draw back for spintronics is the lowest recorded switching energy to flip electron spins between their up or down states to 1s and 0s in binary computer instructions, is still more than two orders of magnitude higher than a CMOS transistor, which severely limits the present applications of spintronic devices. This CAREER project is focused on exploring novel voltage effects to greatly reduce the switching energy of spin-based devices. By successfully demonstrating ultra-low energy switching, this project broadly impacts a wide range of spintronic devices as well as emergent technologies such as wearable computers and the Internet of Things, for which zero power consumption in the standby state is critical and highly desired. The multidisciplinary nature of the research impacts multiple levels of education, from high school to graduate students. The education activities build on a proven plan to encourage and inspire underrepresented minority students in local high schools to pursue STEM majors in college. Moreover, the PI will leverage this CAREER research to continue his outreach efforts to improve the general public's understanding of spintronics through activities such as 'Physics Open House' and 'Physics Phun Nite'.This CAREER award explores energy-efficient switching mechanisms in spintronic structures. Three different, but complementary approaches will be studied: (1) switching based on voltage-controlled interlayer exchange coupling; (2) switching based on voltage-induced effective field; and (3) switching based on voltage-assisted spin transfer torque. These three switching scenarios are studied under the context of voltage-controlled anisotropy and voltage-controlled magnetism. Voltage-controlled anisotropy is an electronic effect where the magnetic anisotropy field can be substantially modified, but the saturation magnetization remains largely the same. Voltage-controlled magnetism is an ionic effect where both the magnetic anisotropy field and the saturation magnetization can be controlled by voltage. The dependence of these effects on the Rashba spin-orbit coupling and Dzyaloshinskii-Moriya Interaction will investigated. Combined with the experiments that characterize the voltage-induced charge redistribution in ferromagnets, a complete understanding on different switching mechanisms will be achieved. Furthermore, these new approaches to dramatically decrease the switching energy will be directly implemented on high quality magnetic tunnel junctions with strong perpendicular magnetic anisotropy, which can not only perform as stand-alone spintronic memories or logic cells, but can serve also as the essential part of many other spintronic devices, such as lateral spin valves and spin-Hall memories. The results obtained in this project will transform our understanding of how magnetoelectric coupling is mediated by both electrons and ions in ultra-thin magnetic films. Success for this project paves a path to ultra-low switching energy spintronic devices that could be complementary, or even superior, to traditional CMOS devices.

自旋电子学明确利用自旋（电子固有的量子力学特性）来实现新颖的功能。自旋电子器件的一个独特优势是它们的非易失性：即使在器件断电后，它们在自旋中存储的信息也会被保留和记住。非易失性对于新一代数字设备尤其重要，其中晶体管尺寸将减小到只有几纳米。在这种纳米尺度上，传统互补金属氧化物半导体（CMOS）晶体管的功耗将主要由漏电流决定；而对于自旋电子结构来说，这种能量浪费可以完全消除。自旋电子学的一个重要缺点是二进制计算机指令中记录的将电子自旋在向上或向下状态之间翻转为 1 和 0 的最低开关能量，仍然比 CMOS 晶体管高两个数量级以上，这严重限制了目前的技术自旋电子器件的应用。该职业项目的重点是探索新颖的电压效应，以大大降低基于自旋的器件的开关能量。通过成功演示超低能耗开关，该项目广泛影响了各种自旋电子器件以及可穿戴计算机和物联网等新兴技术，其中待机状态下的零功耗至关重要且非常迫切。该研究的多学科性质影响着从高中到研究生的多个层次的教育。这些教育活动建立在一项行之有效的计划的基础上，旨在鼓励和激励当地高中代表性不足的少数族裔学生在大学攻读 STEM 专业。此外，PI 将利用这项职业研究继续其外展工作，通过“物理开放日”和“物理 Phun Nite”等活动提高公众对自旋电子学的理解。该职业奖探索自旋电子结构中的节能开关机制。将研究三种不同但互补的方法：（1）基于压控层间交换耦合的切换； (2)基于电压感应有效场的切换； (3)基于电压辅助自旋转移矩的切换。这三种开关场景是在压控各向异性和压控磁性的背景下研究的。电压控制各向异性是一种电子效应，其中磁各向异性场可以显着改变，但饱和磁化强度基本保持不变。压控磁是一种离子效应，磁各向异性场和饱和磁化强度都可以通过电压控制。我们将研究这些效应对 Rashba 自旋轨道耦合和 Dzyaloshinskii-Moriya 相互作用的依赖性。结合表征铁磁体中电压感应电荷重新分布的实验，将实现对不同开关机制的完整理解。此外，这些大幅降低开关能量的新方法将直接在具有强垂直磁各向异性的高质量磁隧道结上实现，它不仅可以作为独立的自旋电子存储器或逻辑单元，还可以作为核心部分许多其他自旋电子器件，例如横向自旋阀和自旋霍尔存储器。该项目获得的结果将改变我们对超薄磁性薄膜中电子和离子如何介导磁电耦合的理解。该项目的成功为超低开关能量自旋电子器件铺平了道路，该器件可以补充甚至优于传统 CMOS 器件。