Current-Driven Domain Wall Motion in Multilayer Nanowires

多层纳米线中电流驱动的畴壁运动

基本信息

批准号：
EP/I011668/1
负责人：
Christopher Marrows
金额：
$ 84.76万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FI011668%2F1
关键词：
Current Driven Domain Wall Motion

项目摘要

The study of spin-transfer torque at a magnetic domain wall continues to be one of the most vibrant areas of research in spintronics, motivated by the prospect of novel memory and logic systems and devices. At heart, the phenomenon is based on a fundamental law of nature: conservation of angular momentum. As an electron moves, as part of a flow of electrical current, through a magnetic domain wall, the direction of magnetisation around it will rotate from that in the first domain to that in the second. The magnetic moment on that electron, which arises from its spin angular momentum, will have to rotate accordingly. This results in a change of angular momentum on the electron by a single quantum unit. This change is compensated for by an equal change in the magnetisation of the metal that is carrying the current. The outcome is that if enough electrons pass through a domain wall, the 'electron wind' will push the wall along, just as a sail is blown along by wind in the atmosphere. The potential for using this effect to write and manipulate data represented magnetically in the next generation of nanoelectronics has lead to proposals for device architectures such as IBM's racetrack memory. At present, research in the field is overwhelmingly dominated by a single material and sample architecture: the lithographically patterned Permalloy nanowire. (Permalloy is a magnetically soft alloy of nickel and iron.) This is in spite of the fact that such nanostructures will probably not form the basis of any eventual device: the domain walls within them are too wide, too complex, and insufficiently rigid. Very high current densities, within an order of magnitude of the point of wire breakdown through electromigration, are needed to move them. From the point of view of basic research, it is clear that only a very restricted number of the possibilities for domain walls in nanowire systems has been investigated with any rigour. We will carry out a wide-ranging study of nanowires fabricated from multilayer films, drawing on years of experience in the preparation and study of such materials. Our attention will be focussed on two main classes of magnetic multilayer. The first class is the so-called synthetic antiferromagnet. Here two magnetic layers sandwich a thin metal spacer layer, through which they are coupled so that their magnetic moments prefer to lie in opposite directions. The lack of a net magnetic moment means that such structures are impervious to moderate magnetic fields and can be packed densely together on a chip without interacting, both attractive for spintronic technologies. Moreover, we have carried out preliminary micromagnetic simulations, which predict narrow, simple domain walls in such structures. The second class is multilayers in which the magnetisation lies perpendicular to the film plane. Recent results that we (and others) have obtained on these systems show that the efficiency of the spin-torque effect is roughly one hundredfold larger in these materials than in Permalloy - but that the defects in the materials lead to wall pinning effects that are larger by the same amount, so that huge current densities are still required. Here we will study the nature of the defects and so learn how to eliminate them, allowing such devices to operate with currents up to one hundred times smaller, leading to ten thousand times less power consumption. We will also investigate the control of the spin-torque effect using local electrical gates, making use of another recent discovery: the fact that in such thin perpendicular layers, a suitable structure incorporating an interface with a dielectric can give rise to electric fields acting as effective magnetic fields on moving electrons, giving rise to a new spin-torque effect through spin-orbit interactions. This will give control of domain wall pinning with a fine spatial and time resolution using voltages, giving the prospect of novel device architectures.

受新型存储器和逻辑系统及器件前景的推动，磁畴壁自旋转移矩的研究仍然是自旋电子学中最活跃的研究领域之一。从本质上讲，这种现象基于自然的基本定律：角动量守恒。当电子作为电流的一部分移动穿过磁畴壁时，其周围的磁化方向将从第一畴中的磁化方向旋转到第二畴中的磁化方向。该电子上由其自旋角动量产生的磁矩必须相应地旋转。这导致单个量子单元的电子角动量发生变化。这种变化可以通过承载电流的金属磁化强度的相同变化来补偿。结果是，如果有足够多的电子穿过磁畴壁，“电子风”就会推动磁畴壁前进，就像风帆在大气中被风吹动一样。利用这种效应在下一代纳米电子学中写入和操作以磁性表示的数据的潜力已经引发了对设备架构的提议，例如 IBM 的赛道存储器。目前，该领域的研究绝大多数以单一材料和样品结构为主：光刻图案化坡莫合金纳米线。（坡莫合金是镍和铁的软磁合金。）尽管这样的纳米结构可能不会形成任何最终器件的基础：它们内部的磁畴壁太宽、太复杂且刚性不够。移动它们需要非常高的电流密度（在电迁移导致的导线击穿点的一个数量级内）。从基础研究的角度来看，很明显，只有非常有限的纳米线系统中畴壁的可能性得到了严格的研究。我们将利用多年来在此类材料的制备和研究方面的经验，对由多层薄膜制成的纳米线进行广泛的研究。我们的注意力将集中在磁性多层的两大类上。第一类是所谓的合成反铁磁体。这里，两个磁性层夹着薄金属间隔层，它们通过该金属间隔层耦合，以便它们的磁矩倾向于位于相反的方向。缺乏净磁矩意味着这种结构不受中等磁场的影响，并且可以在芯片上密集地封装在一起而不会相互作用，这对于自旋电子技术来说都是有吸引力的。此外，我们还进行了初步的微磁模拟，预测了这种结构中狭窄、简单的磁畴壁。第二类是多层膜，其中磁化强度垂直于薄膜平面。我们（和其他人）在这些系统上获得的最新结果表明，这些材料中的自旋扭矩效应的效率大约比坡莫合金大一百倍，但材料中的缺陷会导致更大的壁钉扎效应相同的量，因此仍然需要巨大的电流密度。在这里，我们将研究缺陷的本质，从而了解如何消除它们，使此类设备能够以小一百倍的电流运行，从而将功耗降低一万倍。我们还将研究使用局部电门控制自旋扭矩效应，利用另一个最近的发现：事实上，在如此薄的垂直层中，结合有电介质的界面的合适结构可以产生充当移动电子的有效磁场，通过自旋轨道相互作用产生新的自旋扭矩效应。这将利用电压以精细的空间和时间分辨率控制畴壁钉扎，从而为新型器件架构带来了前景。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer.

DOI：
10.1038/ncomms9957
发表时间：
2015-12-08
期刊：
Nature communications
影响因子：
16.6
作者：
Benitez MJ;Hrabec A;Mihai AP;Moore TA;Burnell G;McGrouther D;Marrows CH;McVitie S
通讯作者：
McVitie S

Measuring and tailoring the Dzyaloshinskii-Moriya interaction in perpendicularly magnetized thin films