Spin@RT: Room Temperature Spintronics

自旋电子学的目的是控制电子自旋，以便它可以用于在新一代电子器件中提供新的功能。在追求这一目标的过程中，有大量令人兴奋的前沿基础物理学，这就是我们将集中精力的地方。第一代自旋电子学已经伴随我们几年了，其中诸如硬盘读头之类的设备是金属基设备的常见示例。半导体在自旋电子学中的应用也有相当多的研究工作，但由于本例中已阐明的原因，我们将集中于金属和氧化物自旋电子学的研究。自旋电子学已经达到了一个阶段，进一步的重大进展需要基于质的不同物理的新一代设备。我们的建议有四个主题。在第一，我们提出利用的新想法，电子波函数的相干性可以保存在整个厚度的外延磁性纳米结构的电荷和自旋的运输过程中。据预测，相干输运将提高磁电阻（MR）超过一个数量级。这种MR单独的改进对自旋电子器件如磁性随机存取存储器（MRAM）的影响将是巨大的。在第二个主题中，我们打算以一种全新的方式使用基于设备的X射线源的分辨率，具体地说，观察由于注入自旋极化电流而导致的贵金属自旋极化的微小但显著的变化。这是第一次直接测量自旋积累将提供详细的信息，自旋电流扭矩目前失踪，但迫切需要的研究中所描述的第三个主题。这种测量将依赖于我们在大面积纳米器件制造、同步辐射和高频测量在微米级波导中的使用方面的专业知识。在第三个主题中，我们将研究的时间和空间的相干性的电流诱导的磁性状态的纳米柱阵列使用迄今未开发的X射线，中子和时间分辨的光学技术，以区分自旋转移力矩的分析模型，并了解丰富的动态行为，最近已经报道。实验和理论之间的密切相互作用将使我们不仅能够理解，而且能够通过选择材料和实验几何形状来操纵动态行为。最后，在第四个主题中，我们将使用纳米纤维从磁阻材料中创建新的纳米线结构，并采用强大的磁性表征工具来观察畴壁的电流感应运动。这将使我们能够解决一些关键的，但有争议的问题，如诱导壁运动所需的最小电流密度，壁速度的内在限制，和畴壁结构的影响。

The aim of spintronics is to control the electron spin so that it can be used to provide new functionality in a new generation of electronic devices. Within the pursuit of this aim there is a great deal of exciting cutting-edge fundamental physics and this is where our efforts will be concentrated. The first generation of spintronics has been with us for several years where devices such as read-heads for hard discs are a commonplace example of a metal-based device. There is also considerable research effort into the use of semiconductors in spintronics, but for reasons made clear in the case, we shall concentrate on metal and oxide spintronic research. Spintronics has reached a stage where further significant progress requires a new generation of devices based on a qualitatively different physics. Our proposal has four major themes. In the first we propose to exploit the new idea that the coherence of electron wave functions may be preserved during the transport of charge and spin across the entire thickness of an epitaxial magnetic nanostructure. It has been predicted that coherent transport will improve the magnetoresistance (MR) by more than an order of magnitude. The impact of such an improvement in MR alone on spintronic devices such as magnetic random access memory (MRAM) will be immense. In the second theme we intend to use the resolution of facility-based x-ray sources in an entirely new way, specifically, to observe the small but significant changes in the spin polarisation of a noble metal that result from injection of a spin-polarised current. This first direct measurement of spin accumulation will provide detailed information on spin-current torque which is currently missing but urgently required for the research described in the third theme. Such measurements will rely on our expertise in large area nano-device fabrication, the use of synchrotron radiation and high frequency measurements in micro-scale waveguides. In the third theme we will study the temporal and spatial coherence of the current-induced magnetic state of nano-pillar arrays using hitherto unexploited x-ray, neutron and time-resolved optical techniques to distinguish between analytical models for spin-transfer torque, and to understand the rich dynamic behaviour that has recently been reported. Close interplay between experiment and theory will allow us not only to understand but also to manipulate the dynamic behaviour through the choice of materials and experimental geometry. Finally, in the fourth theme, we will use nanofabrication to create novel nanao-wire structures from magnetoresistive materials and employ a powerful collection of magnetic characterisation tools to observe the current-induced motion of domain walls. This will allow us to resolve a number of critical but controversial issues such as the minimum current density required to induce wall motion, the intrinsic limit upon wall velocity, and the influence of domain wall structure.