Non-local spin transport across electronic phase transitions

纳米磁性和自旋电子学（操纵电子的自旋）的成功已经使材料的磁性设计成为可能。然而，这些成就更加强调精确控制电子自旋的传输。这一点在硬盘驱动器读头中最为明显，读头尺寸的持续减小严重限制了隧道磁阻传感器的未来使用，这是ICT行业的一个重大挑战。现在正在积极寻求低阻抗替代品，全金属器械重新成为关注的焦点。值得注意的是，尽管像读头这样的自旋电子器件无处不在，但我们对纳米尺度下金属系统中自旋输运的理解仍然存在明显的差距。即使在磁阻器件中使用的（相对）简单的铁磁和非磁性材料中，最近的结果也对我们在这一水平上的理解提出了质疑。这对它们的未来使用提出了一些重大挑战。除了这些材料之外，我们对它们的了解就更少了，一般来说，精确的电子相位和自旋输运之间更广泛的相互作用才刚刚开始被探索。这种限制对当前技术的影响是显而易见的，其中绝大多数自旋电子器件仅限于考虑远程铁磁材料的操纵，例如在存储应用中。事实上，除了铁磁开关之外，用自旋控制状态的可能性可能会给自旋电子器件带来全新的功能，可能会导致变革性的新技术--这是一个令人兴奋的前景。我们将首先探索纯自旋输运，使用一种称为“非局部自旋阀”的设备作为研究平台，以结合复杂的磁性材料。最初，这将涉及定制自旋通道特性，以系统地揭示特定缺陷在限制自旋输运中的作用-这是增强金属器件中自旋信号的关键结果。然后，我们将了解电子相和自旋扩散之间的相互作用，试图探测自旋输运通过主机的基本相变，包括自旋玻璃冻结，金属绝缘和铁磁反铁磁。通过这样做，丰富的新信息的相互作用的自旋电流与相位将被揭示。通过一些自旋生成技术，我们将研究的扭矩的作用，从吸收自旋电流稳定阶段，提高临界温度，移动相边界和诱导临界波动在主机这些过渡。通过使用NLSV进行这些研究，我们将能够在一个新的但与技术相关的环境中探索这种影响。

The successes of nanoscale magnetism and spintronics (where the spin of the electron is manipulated) have been enabling for materials-by-design magnetism. However, these accomplishments have placed ever more emphasis on precisely controlling the transportation of electron spin. This is nowhere more critically seen than in the case of hard disk drive read heads, where continued reduction in read head size places serious limits to the future use of tunnel magneto-resistance sensors - a major challenge for the ICT industry. Low impedance alternatives are now actively sought, with all-metallic devices returning to the forefront of interest. Remarkably, despite the ubiquity of spintronic devices like read heads, there remain stark gaps in our understanding of spin transport in metallic systems at the nanoscale. Even in the (relatively) simple ferromagnetic and non-magnetic materials used in magnetoresistive devices, recent results have called into question our understanding at this level. This imposes a number of substantial challenges for their future use. Moving beyond these materials even less is known and, in general, the wider interplay between precise electronic phase and spin transport is only beginning to be probed. The impact of such limitations to current technology is readily seen, with the vast majority of spintronic devices limited to considering only the manipulation of long-range ferromagnetic materials, e.g. in storage applications. Indeed, the possibility of controlling state with spin, beyond ferromagnetic switching, could bring entirely new functionality to spintronic devices, potentially leading to transformative new technologies -- an exciting prospect.The aim of this proposal is to explore mediating phase transitions using pure spin currents. We will first explore pure spin transport, using a device known as a 'non-local spin valve' as a research platform to incorporate complex magnetic materials. Initially this will involve tailoring spin channel properties to systematically bring to light the role of specific defects in limiting spin transport -- crucial results for enhancing spin signals in metallic devices. We will then move to understand the interplay between electronic phase and spin diffusion, attempting to probe spin transport across a host of fundamental phase transitions, including spin glass freezing, metallic to insulating and ferro- to antiferro-magnetic. By doing so, a wealth of new information on the interaction of spin currents with phase will be revealed. Through a number of spin generation techniques, we will examine the role of the torques from absorbed spin currents in stabilising phases, enhancing critical temperatures, moving phase boundaries and inducing critical fluctuations across a host of these transitions. By using the NLSV for these studies, we will be able to explore such effects in a novel but technologically relevant environment.