Spin@RT: Room Temperature Spintronics

自旋电子学的目的是控制电子自旋，这样它就可以用来在新一代电子设备中提供新的功能。在追求这一目标的过程中，有大量令人兴奋的尖端基础物理，这是我们将集中努力的地方。第一代自旋电子学已经伴随我们好几年了，其中硬盘读取头等设备是基于金属的设备的常见例子。关于半导体在自旋电子学中的应用也有相当大的研究努力，但由于案件中明确的原因，我们将专注于金属和氧化物自旋电子学的研究。自旋电子学已经到了一个阶段，要想取得更大的进步，就需要基于本质上不同的物理原理的新一代设备。我们的建议有四个主要主题。首先，我们提出了一种新的想法，即在整个厚度的外延磁性纳米结构的电荷和自旋的传输过程中，电子波函数的相干性可以被保持。已有预测表明，相干输运将使磁阻提高一个数量级以上。仅MR方面的这种改进对诸如磁随机存取存储器(MRAM)的自旋电子器件的影响将是巨大的。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。这种对自旋累积的首次直接测量将提供关于自旋-电流扭矩的详细信息，该扭矩目前尚不存在，但对于第三个主题中描述的研究是迫切需要的。这样的测量将依赖于我们在大面积纳米器件制造、同步辐射的使用和微米级波导中的高频测量方面的专业知识。在第三个主题中，我们将使用迄今尚未开发的X射线、中子和时间分辨光学技术来研究纳米柱阵列电流感生磁态的时间和空间相干性，以区分自旋转移扭矩的分析模型，并了解最近报道的丰富的动力学行为。实验和理论之间的密切相互作用将使我们不仅能够理解，而且还可以通过选择材料和实验几何来操纵动态行为。最后，在第四个主题中，我们将利用纳米加工技术从磁阻材料中创造出新颖的纳米线结构，并使用一系列强大的磁性表征工具来观察电流诱导的磁畴壁运动。这将使我们能够解决一些关键但有争议的问题，如诱导壁面运动所需的最小电流密度，壁面速度的内在限制，以及磁区壁面结构的影响。

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.