SPINCURRENT: Domain Walls and Spin-Polarised Currents

在磁性材料中产生、操纵和检测自旋极化电流的能力，导致了自旋电子学领域活动的爆炸式增长。自旋电子学是利用电子的自旋和电荷来处理和存储信息的。关于自旋电子学的前景和未来影响的文章在《新科学家》、《科学美国人》、《IEEE频谱》、《今日物理学》和《物理世界》等普通读者杂志上比比皆是。科学影响的证据可以在《自然》、《科学》和《物理评论快报》等期刊上的大量研究文章中找到（1988年PRL报告发现巨磁电阻是有史以来被引用率最高的第六位），而IBM、日立、西门子、飞思卡尔、希捷等公司在自旋电子学研究方面的巨大收入（每年数十亿美元）是基于他们已经从早期利用基本巨磁电阻（GMR）自旋电子效应的设备（如硬盘自旋阀头）中获得的，以及未来技术突破预期的收入。利用自旋的设备可以提供更高的速度、更低的功耗和更密集的缩放，以及提供全新功能的机会，例如非易失性数据存储或可重构逻辑门。畴壁是一种天然存在的磁性纳米结构，在本提案中，我们正在寻求资金，以开展一项广泛的研究，研究自旋极化电流的纳米级磁性器件中畴壁的相互作用。这两个对象之间存在互反关系：一方面，畴壁可能会导致自旋极化电子在穿过畴壁时产生额外（或减少）散射，当磁化饱和到单一畴态时，畴壁被移除，从而引起电阻的变化。另一方面，当电子经历这种散射时，它们的波矢量和/或自旋状态将发生变化，相关的线动量或角动量将转移到壁上，从而产生力或扭矩。这会引起电流引起的壁面运动。这两种影响，以及巨大的科学兴趣，都具有重大的技术前景。

The ability to generate, manipulate and detect spin-polarised electrical currents in magnetic materials has resulted in an explosion of activity in the now burgeoning field of spintronics, where the spin, as well as the charge, of the electron is used to process and store information. Articles about the promise and future impact of spintronics are commonplace in general audience magazines such as New Scientist, Scientific American, IEEE Spectrum, Physics Today, and Physics World. Evidence for the scientific impact is found in the high number of research articles in journals such as Nature, Science and Physical Review Letters (the 1988 PRL reporting the discovery of giant magnetoresistance is the sixth most highly cited of all time), whilst the massive investment of companies such as IBM, Hitachi, Siemens, Freescale, Seagate etc. in spintronics-based research is based on the huge revenue (billions of $ p.a.) that they are already reaping from early devices exploiting the basic Giant Magnetoresistance (GMR) spintronic effect such as hard disc spin-valve heads, and the revenue that is expected from future technological breakthroughs. Devices taking advantage of spin offer operation at higher speeds, lower power, and denser scaling, as well as giving the opportunity of entirely new functionality, such as non-volatile data storage or reconfigurable logic gates . A domain wall is a naturally occurring magnetic nanostructure and in this proposal we are seeking funding to launch a wide ranging study of the interactions of domain walls in nanoscale magnetic devices with spin-polarised currents. There is a reciprocal relationship between these two objects: on the one hand, the domain wall may cause additional (or reduced) scattering of the spin-polarised electrons as they traverse it, giving rise to a change in resistance when the magnetisation is saturated to a single domain state and the wall is removed. On the other, as the electrons undergo this scattering their wavevector and/or spin state will change and the associated amount of linear or angular momentum is transferred to the wall, giving rise to a force or torque. This can cause current-induced wall motion. Both of these effects, as well as being of great scientific interest, are of substantial technological promise.