Spintronics with Yttrium Iron Garnets - From Fundamental Physics to Device Concepts

使用钇铁石榴石的自旋电子学 - 从基础物理到设备概念

• 批准号: 1231598
• 负责人: Mingzhong Wu
• 金额: $ 33万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1231598&HistoricalAwards=false
• 关键词: Spintronics; Yttrium; Iron; Garnets; Fundamental

Abstract: Recent work demonstrates that one can transmit spin currents into and out of yttrium iron garnet thin films, as well as use such films to generate spin currents. This demonstration opens a new research field of yttrium iron garnet-based spintronics. This new program will address four issues in this emerging field: (1) spin pumping at yttrium iron garnet/normal metal interfaces; (2) relaxation control in yttrium iron garnet films through interfacial spin scattering and its device applications; (3) spin-wave amplification through interfacial spin scattering and potential device applications; and (4) spin Seebeck effects and potential device applications. Topic (1) addresses the efficiency of spin angular momentum transfer across yttrium iron garnet/normal metal interfaces. Topics (2) and (3) consider the scattering of spin-polarized electrons off the surface of a yttrium iron garnet film and study the effects of such interfacial spin scattering on both uniform and non-uniform modes in the film, and make use of the interfacial spin scattering and yttrium iron garnet thin films to demonstrate a new type of spin torque oscillator as well as low-loss delay lines and phase shifters. Topic (4) studies the spin Seebeck effect in yttrium iron garnet films in a perpendicular configuration in which the temperature gradient is perpendicular to both the film plane and the magnetization. Under Topic (4), work is also planned to demonstrate a new spin torque oscillator that relies on thermally induced interfacial angular momentum transfer. Although several device concepts will be demonstrated, the new program does not include plans for the implementation and integration of spintronic devices such that the workload is reasonable. The new program is supported by preliminary work and collaborations with three leading groups in spintronics. Education activities include teaching spintronics in Advanced Solid State Physics course.Intellectual Merits: (1) This program will yield the first results on fundamental physics underlying (i) spin angular momentum transfer across yttrium iron garnet/normal metal interfaces, (ii) interactions between spin currents in normal metal layers and excitations in yttrium iron garnet films, and (iii) relaxation control through thermally induced angular momentum transfer. (2) The program will demonstrate new methods for relaxation control in magnetic insulators. Such control is highly desirable because magnetization relaxation not only plays a critical role in the dynamics of spin-based devices but also sets a natural limit to the response time of a device. (3) Two new types of spin torque oscillators will be demonstrated. (4) The program will yield novel approaches for spin-wave amplifications and thereby opens the door to a new class of spin-wave devices. Broader Impacts: The program will touch on several fundamental issues and will therefore have a significant impact on the advancement of the new research field of yttrium iron garnet spintronics. The technological significance of yttrium iron garnet spintronic devices originates from two features of yttrium iron garnets: (1) extremely small damping and (2) electrically insulating property. The small damping, for example, will allow for the development of new spin torque oscillators that exhibit much narrower spectral linewidth and much larger signal-to-noise ratios than ferromagnetic metal-based oscillators. The advancement of spin wave-based microwave devices and logic devices is bottlenecked by spin-wave damping. The new approaches for spin-wave amplification will promote the development of these devices. The program will provide research opportunities for graduate, undergraduate, and high school students. Outreach to high schools in Colorado will be accomplished through the Colorado State University Little Shop of Physics program. The results from this program will be disseminated broadly through conference presentations, publications, and visits to national laboratories and industry.

摘要：最近的研究表明，人们可以将自旋电流传输到和流出钇铁石榴石薄膜，并使用这种薄膜来产生自旋电流。这一演示开辟了钇铁石榴石基自旋电子学的新研究领域。这一新计划将解决这一新兴领域中的四个问题：(1)Y-Fe石榴石/正常金属界面的自旋泵浦；(2)通过界面自旋散射的弛豫控制及其器件应用；(3)通过界面自旋散射的自旋波放大和潜在的器件应用；以及(4)自旋塞贝克效应和潜在的器件应用。主题(1)讨论了Y-Fe-石榴石/正常金属界面自旋角动量转移的效率。主题(2)和(3)考虑了自旋极化的电子在钇铁石榴石薄膜表面的散射，研究了这种界面自旋散射对薄膜中均匀模和非均匀模的影响，并利用界面自旋散射和钇铁石榴石薄膜展示了一种新型的自旋扭矩振荡器以及低损耗延迟线和移相器。课题(4)研究了温度梯度与薄膜平面和磁化强度垂直的垂直位形中的自旋Seebeck效应。在主题(4)下，还计划展示一种新的自旋扭矩振荡器，该振荡器依赖于热诱导的界面角动量转移。尽管将演示几个设备概念，但新计划不包括实施和集成自旋电子设备的计划，从而使工作量是合理的。新计划得到了前期工作的支持，并与自旋电子学的三个领先团队进行了合作。教学活动包括教授高级固态物理课程中的自旋电子学。智力优势：(1)这项计划将产生关于基础物理的第一个结果，其基础是(I)Y铁石榴石/正常金属界面上的自旋角动量转移，(Ii)正常金属层中的自旋电流与Y铁石榴石薄膜中的激发之间的相互作用，以及(Iii)通过热诱导角动量转移来控制弛豫。(2)该程序将演示磁性绝缘子松弛控制的新方法。这样的控制是非常可取的，因为磁化松弛不仅在基于自旋的器件的动力学中起着关键作用，而且还对器件的响应时间设定了自然的限制。(3)将演示两种新型的自旋扭矩振荡器。(4)该计划将产生新的自旋波放大方法，从而为一类新的自旋波装置打开大门。更广泛的影响：该计划将涉及几个基本问题，因此将对新的钇铁石榴石自旋电子学研究领域的进展产生重大影响。钇铁石榴石自旋电子器件的技术意义源于钇铁石榴石的两个特性：(1)极小的阻尼和(2)电绝缘性能。例如，较小的衰减将允许开发新的自旋扭矩振荡器，与铁磁性金属振荡器相比，这种振荡器具有更窄的谱线宽度和更高的信噪比。自旋波衰减是制约基于自旋波的微波器件和逻辑器件发展的瓶颈。新的自旋波放大方法将促进这些器件的发展。该计划将为研究生、本科生和高中生提供研究机会。科罗拉多州高中的外展将通过科罗拉多州立大学物理小商店计划完成。该计划的成果将通过会议报告、出版物和对国家实验室和工业的访问广泛传播。