Spin Transport Studies In Band And Interface Tailord Materials: Towards Total Spin Polarization For Spin Electronics

带和界面定制材料中的自旋输运研究：自旋电子学的总自旋极化

• 批准号: 0504158
• 负责人: Jagadeesh Moodera
• 金额: $ 43.75万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-11-01 至 2012-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0504158&HistoricalAwards=false
• 关键词: Spin; Transport; Studies; Band; Interface

Nontechnical:Enabled by advances in basic research as well as driven by a rising demand for ultra-high density magnetic storage, there is an enormous interest of late in devices based on electron spin transport. In this NSF sponsored project we will investigate fundamental properties as well as applied aspects of magnetism related to this, with an expected impact on the field at the basic level as well as the future spin-based information technology. To reach this goal, spin-polarized transport studies of several novel systems will carried out, and to understand and manipulate the spin polarization, P (the degree to which transport electrons are spin polarized), and develop "tailored" materials. For example, we will explore the Cobalt-Iron_Boron alloy system, which recently demonstrated very large tunneling magnetoresistance (TMR) values (the higher it is the more useful for application), to achieve even higher P and TMR values. This material system remains largely unexplored and this study should open the way for candidate materials where P approaches 100%, without the interface problems of a half metal ferromagnet. Ferromagnet-insulator interface bonding is crucial in controlling the magnitude of P. We will aim at controlling this bonding for higher P. The possibility to make structures on a nanometer scale with well-tailored materials and interfaces will allow us to create new materials that show suitable properties. In particular, spin-polarized transport through quantum islands gives rise to novel effects such as spin-resonant tunneling, which can greatly enhance the TMR (observed in our laboratory) with the possibility of making spin transistors. The education of students in science through this outreach program will continue in an effective way to meet the national need for enhanced science education. Continuing the tradition, along with training graduate students and postdoctoral researchers, undergraduates and high-school students extensively participate in this research. It will enormously benefit these younger generation by getting trained for future spin based nano technology.Technical:In this NSF supported individual project a series of investigations are proposed that focus on fundamental properties as well as applied aspects of magnetism, which will benefit both at the basic level as well as for the future spin-based information technology. Spin-polarized transport studies of several novel systems will be done to understand and manipulate the spin polarization (P), necessary for future spin devices. The role of the ferromagnet-insulator interface bonding is crucial in controlling the magnitude of P. Our aim is to control this bonding and explore novel tunnel barriers to achieve higher P, including the exploration of the Co-HfO2 system, predicted to have P=100%. Spin filter tunneling is one of the few ways in which near 100% P (demonstrated in our group in the past), which will be explored for achieving P=100% above LHe temperatures. Based on the electronic structures of the constituent CoB and FeB alloys, we believe it is possible to "tailor" the (Co,Fe)-B band hybridization to achieve even higher P and tunnel magnetoresistance (TMR) values. This material system remains largely unexplored and should open the way for candidate materials with high P, without the interface problems of a half metal ferromagnet. Exploiting dimensionality on a nanoscale, in particular, spin-polarized transport through quantum islands can give rise to novel effects such as spin-resonant tunneling, which can greatly enhance the TMR, as has been observed in our laboratory. Double magnetic tunnel junctions exploiting non-equilibrium spin accumulation and ballistic spin transport will be explored, with potential for novel devices such as spin transistors. As in the past in addition to graduate students, postdoctoral researchers and visiting scientists, undergraduates and high-school students participate in this research program. The education of students in science through this outreach program will continue in an effective way to meet the national need for science education.

非技术性：由于基础研究的进步以及对超高密度磁存储需求的不断增长，最近对基于电子自旋输运的设备产生了巨大的兴趣。在这个NSF赞助的项目中，我们将研究基本性质以及与此相关的磁性的应用方面，并在基本水平上对该领域以及未来基于自旋的信息技术产生预期的影响。为了实现这一目标，将对几种新型系统进行自旋极化输运研究，并理解和操纵自旋极化P（输运电子自旋极化的程度），并开发“定制”材料。 例如，我们将探索钴-铁_硼合金系统，该系统最近显示出非常大的隧道磁阻（TMR）值（越高对应用越有用），以实现更高的P和TMR值。这种材料系统在很大程度上尚未探索，这项研究应该为P接近100%的候选材料开辟道路，而没有半金属铁磁体的界面问题。 铁磁体-绝缘体界面键合在控制P的大小方面至关重要。我们的目标是控制这种键合以获得更高的P。利用定制的材料和界面在纳米尺度上制造结构的可能性将使我们能够创造出具有合适性能的新材料。特别是，通过量子岛的自旋极化传输产生了诸如自旋共振隧穿等新效应，这可以大大增强TMR（在我们实验室中观察到），并有可能制造自旋晶体管。通过这一推广方案对学生进行科学教育将继续有效地满足国家对加强科学教育的需要。延续传统，沿着培养研究生和博士后研究人员，本科生和高中生广泛参与本研究。这将极大地有利于这些年轻一代通过得到培训，为未来的自旋为基础的纳米技术。技术：在这个NSF支持的个人项目提出了一系列的调查，重点是基本属性以及应用方面的磁性，这将有利于在基础水平，以及为未来的自旋为基础的信息技术。几个新系统的自旋极化输运的研究将进行理解和操纵的自旋极化（P），必要的未来自旋器件。铁磁-绝缘体界面键合的作用是至关重要的，在控制P的大小。我们的目标是控制这种键合，并探索新的隧道势垒，以实现更高的P，包括探索的Co-HfO 2系统，预测有P= 100%。自旋过滤器隧穿是接近100% P的少数方法之一（过去在我们的小组中证明），这将被探索以在LHe温度以上实现P=100%。基于组分Co B和Fe B合金的电子结构，我们相信有可能“定制”（Co，Fe）-B带杂化以实现甚至更高的P和隧道磁阻（TMR）值。这种材料系统仍然在很大程度上未被探索，应该开辟了高P的候选材料的道路，没有半金属铁磁体的界面问题。利用纳米尺度上的维度，特别是通过量子岛的自旋极化传输可以产生新的效应，如自旋共振隧穿，这可以大大增强TMR，正如我们实验室所观察到的那样。利用非平衡自旋积累和弹道自旋输运的双磁隧道结将被探索，具有诸如自旋晶体管之类的新型器件的潜力。与过去一样，除了研究生、博士后研究人员和客座科学家之外，本科生和高中生也参与了该研究项目。通过这一推广方案对学生进行科学教育将继续以有效的方式满足国家对科学教育的需求。