GOALI: Novel Magnetic Structures for Energy-Efficient Spin-Based Electronic Devices

摘要：自旋电子学，通常被称为自旋电子学，利用电子的自旋和电荷来提供功能更强、更节能的器件。近年来，自旋传递力矩的概念因其在计算机存储器和基于自旋电子学的逻辑器件中提供高密度而受到广泛关注。然而，现有的电子自旋转矩效率较低，因此需要高电流才能在器件中存储信息。阿拉巴马大学和IBM研究中心的大学-工业团队提出了一项关于新型自旋电子器件结构的研究，该结构利用磁性多层结构中温差产生的自旋电流来产生自旋传递扭矩，这种方法可能非常有效。了解界面处的自旋转移特性并成功演示所提出的概念可以大大提高自旋基器件的能量效率，从而开辟新的应用。拟议的项目需要多学科的努力，将对科学知识、教育推广和基础设施作出重大贡献。项目人员将在与拟议的研究有关的几项正在进行的教育和外联活动中发挥关键作用。这些措施包括与当地学校合作，促进高中生参与研究、公众参观和示范。拟议的项目将研究一种新的自旋电子器件概念，解决当前自旋转移扭矩器件所需的高写入电流问题。项目目标背后的物理原理是基于最近的一项理论预测，该预测概述了一种热路径，可以提高切换超薄磁层所需的自旋扭矩效率。关键材料是一种磁绝缘体，它在热激发时产生自旋波（或磁振子）。当磁振子将自旋信息传递给相邻导电间隔层中的传导电子时，最终结果是自旋极化电流的放大。所提出的热磁方法具有在自旋转移扭矩器件中实现一到两个数量级更大的量子产率的潜力。这项研究合作将从根本上发展新的知识和理解理论上预测的由基于氧化物的磁绝缘体内产生的磁振子的热自旋扭矩效应。候选异质结构中自旋-扭矩和自旋-泵送行为的基础研究应进行。铁磁共振、磁光技术和图像化纳米结构的磁显微镜技术将阐明热自旋传递扭矩效应，并量化热自旋电流转换效率。独特的合成策略应寻求开发磁性尖晶石氧化物和石榴石薄膜的低温生长过程，这有望成为整合不同材料的关键。

Abstract:Spin-based electronics, commonly referred to as spintronics, exploits the spin of the electron in addition to its charge to provide more functional and energy-efficient devices. In recent years the concept of spin-transfer torque has gained much attention since it offers high density in computer memory and logic devices based on spintonics. However, existing electronic spin-torque efficiency is low, and, as a result, requires high current for information storage in devices. This proposal from the university-industry team at the University of Alabama and IBM Research Center puts forward an investigation into novel spin-based electronic device structures that utilizes a potentially extremely efficient means of generating spin-transfer torque - by spin currents generated by a temperature difference in magnetic multilayer structures. Understanding the spin transfer properties at the interfaces and successful demonstration of the proposed concept can lead to considerable improvement in the energy efficiency of spin-based devices that will open up new applications. The proposed project requires a multidisciplinary effort that will make significant contributions to scientific knowledge, education outreach and infrastructure. Project personnel will play a key role in several ongoing education and outreach activities related to the proposed research. These include collaboration with local schools to facilitate participation by high school students in research, public tours and demonstrations.The proposed project will investigate a novel spintronic device concept that addresses the issue of high write currents required for present spin-transfer torque devices. The physical principle behind the project goals is based on a recent theoretical prediction that outlines a thermal route of enhancing the spin torque efficiency required to switch an ultra-thin magnetic layer. The key material is a magnetic insulator which generates spin waves (or magnons) when thermally excited. The net result is amplification in the spin-polarized current when the magnons transfer spin information to the conduction electrons in an adjoining conducting spacer layer. The proposed thermagnonic method has the potential for achieving one to two orders-of-magnitude greater quantum yield in spin-transfer torque devices. The research collaboration will develop fundamentally new knowledge and understanding of the theoretically predicted thermal spin-torque effect from magnons generated within oxide-based magnetic insulators. Fundamental investigations of spin-torque and spin-pumping behavior in candidate heterostructures shall be undertaken. Ferromagnetic resonance, magneto-optic techniques, and magnetic microscopy of patterned nanostructures shall elucidate the thermal spin-transfer torque effect and quantify the thermal-to-spin-current conversion efficiency. Unique synthetic strategies shall be pursued that exploit low temperature growth processes for magnetic spinel oxide and garnet films, which is expected to be crucial for integrating a disparate set of materials.