Magnetoresistive sensors for magnetic domain wall technologies

磁性纳米技术的最新发展已经出现了新的器件概念，可以在某些应用中挑战传统的硅基微电子。磁性设备相对于其他技术的一个关键优势是，它们通常不需要电力来保存数据。在特定情况下，磁性纳米技术设备还可以提供更高的设备密度、更低的功耗、更好的可靠性或比它们的竞争对手更多的功能。其中一些磁性装置是用薄铁磁层制成的，由只有几个原子厚的非磁性金属间隔层隔开。上层和下层将具有不同的磁化方向，并且由于被称为“巨磁电阻”（GMR）的效应，整个设备的电阻取决于它们的相对方向。这些设备已经在许多应用中广泛用作磁场传感器，例如在计算机和汽车产品中。其他基于平面磁性纳米线网络的技术正在被开发，通常只有一个单一的磁性层，没有间隔层。导线的几何形状很重要，因为这限制了磁化沿导线轴线的两个方向之一。这为表示数字信息的二进制数提供了一个简单的系统。相反的磁化方向可以相遇，在这种情况下，它们被一个称为“畴壁”的过渡区域隔开。畴壁可以很容易地创建或移除，并通过纳米线中的磁场或电流在纳米线网络中传播。通过这种方式，信息通过电路写入、删除和发送，无论是传感器、存储器还是逻辑器件。然而，为了使这些设备在商业上取得成功，我们必须以与现代电子兼容的形式读出磁性数据。到目前为止还没有任何这方面的证明。在这个合作研究项目中，我们将通过开发一种纳米级设备来读取磁性纳米线中的数据来解决这一缺陷。我们最近的计算表明，畴壁的磁场在纳米线附近非常高。我们将利用这个磁场改变附近传感器的磁结构，并使用GMR检测这些变化。这将是磁性纳米线技术的重要一步，因为它将允许纳米线器件完全集成为独立的集成电路。我们还将使用这些传感器进行科学测量，以提高我们对磁性纳米线中畴壁行为的理解。该项目的申请者在纳米制造、磁性纳米线、GMR材料和纳米级磁性系统的计算机建模方面汇集了世界领先的经验，使其成为承担如此具有挑战性的项目的理想团队。

Recent developments in magnetic nanotechnology have seen new device concepts emerge that could challenge traditional silicon-based microelectronics in certain applications. A key advantage of magnetic devices over alternative technologies is that they generally do not require power to retain data. In specific cases, magnetic nanotechnology devices may also offer higher device density, lower power consumption, improved reliability or additional functionality compared with their rivals. Some of these magnetic devices are made using thin ferromagnetic layers separated by a non-magnetic metal spacer layer just a few atoms thick. The upper and lower layer will have different magnetisation directions and the electrical resistance of the overall device depends on their relative orientation due to an effect known as 'giant magnetoresistance' (GMR). Already, these devices are widely used as magnetic field sensors in many applications, e.g. in computers and automotive products. Other technologies are being developed based upon networks of planar magnetic nanowires, usually with just a single magnetic layer and no spacer layers. The geometry of the wires is important, since this restricts magnetisation to lie in one of two directions along the wire axis. This provides a simple system for representing the binary numbers of digital information. Opposite magnetisation directions can meet, and where this happens, they are separated by a transition region known as a 'domain wall'. Domain walls can be easily created or removed and made to propagate through a nanowire network using magnetic fields or electrical currents in the nanowires. In this way, information is written, deleted and sent through a circuit, be it a sensor, memory or logic device. However, for these devices to be commercially successful, we must have read-out of the magnetic data in form compatible with modern electronics. There have not been any demonstrations of this to date. In this collaborative research programme, we will address this deficiency by developing a nanoscale device to read data in magnetic nanowires. Our recent calculations have shown that the magnetic field from domain walls is very high close to the nanowires. We will use this field to change the magnetic configuration of a nearby sensor and detect these changes using GMR. This will be a significant step for magnetic nanowire technologies since it will allow nanowire devices to be fully integrated as stand-alone integrated circuits. We will also use these sensors for scientific measurements to improve our understanding of the behaviour of domain walls in magnetic nanowires.The applicants for this project bring together world-leading experience in nanofabrication, magnetic nanowires, GMR materials and computer modelling of nanoscale magnetic systems, making this the ideal team to undertake such a challenging project.