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.

自旋电子学明确地利用自旋（电子的固有量子力学性质）来实现新的功能。自旋电子器件的一个独特优势是它们的非易失性：它们在自旋中存储的信息即使在从器件中移除电源后也会保留和记忆。非易失性对于新生代的数字器件尤其重要，在这些数字器件中，晶体管的尺寸将减小到只有几纳米。在这种纳米尺度下，传统互补金属氧化物半导体（CMOS）晶体管的功耗将由漏电流主导;而对于自旋电子结构，可以完全消除这种能量浪费。自旋电子学的一个重要缺陷是在二进制计算机指令中将电子自旋在其向上或向下状态之间翻转到1和0的最低记录切换能量仍然比CMOS晶体管高两个数量级以上，这严重限制了自旋电子器件的当前应用。这个CAREER项目的重点是探索新的电压效应，以大大降低自旋器件的开关能量。通过成功展示超低功耗开关，该项目广泛影响了各种自旋电子器件以及新兴技术，如可穿戴计算机和物联网，待机状态下的零功耗是至关重要的，也是非常期望的。该研究的多学科性质影响了从高中到研究生的多个教育层次。教育活动建立在一个行之有效的计划，以鼓励和激励当地高中代表性不足的少数民族学生在大学攻读STEM专业。此外，首席研究员将利用这项CAREER研究继续他的外展工作，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。这项CAREER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）基于电压控制的层间交换耦合的开关;（2）基于电压诱导的有效场的开关;和（3）基于电压辅助的自旋转移力矩的开关。这三个开关的情况下，电压控制的各向异性和电压控制的磁性的背景下进行研究。电压控制的各向异性是一种电子效应，其中磁各向异性场可以基本上被修改，但饱和磁化强度基本上保持不变。电压控制磁性是一种离子效应，其中磁各向异性场和饱和磁化强度都可以由电压控制。这些影响的Rashba自旋轨道耦合和Dzyaloshinskiii-Moriya相互作用的依赖性将被调查。结合铁磁体中电压诱导电荷重新分布的实验，将对不同的开关机制有一个完整的理解。此外，这些新的方法，以显着降低开关能量将直接实现在高品质的磁性隧道结具有强垂直磁各向异性，它不仅可以作为独立的自旋电子存储器或逻辑单元，但也可以作为许多其他自旋电子器件，如横向自旋阀和自旋霍尔存储器的重要组成部分。在这个项目中获得的结果将改变我们的理解磁电耦合是如何介导的电子和离子在超薄磁性薄膜。该项目的成功为超低开关能量自旋电子器件铺平了道路，这种器件可以与传统CMOS器件互补，甚至上级。