Synthetic Antiferromagnetic Skyrmions

在这个项目中，我们将稳定手性合成反铁磁多层膜中被称为Skyrmions的小圆形磁区，并研究它们的电流驱动动力学。该项目是基于我们团队最近的两项突破：我们能够在适当设计的单一手性垂直磁化层中稳定Skyrmions作为拓扑保护结构(使其抗湮灭)，以及能够在简单的面内磁化合成反铁磁体中以低电流密度移动耦合的拓扑缺陷(域壁)。尽管传统的Skyrmions是各种新型信息存储和处理设备的有趣候选者，这些设备提供了极低功率运行的前景，但由于拓扑阻尼，它们预计会在小尺寸下缓慢移动，并被导致Skrmion Hall效应的Magnus力转向与当前驱动方向的角度。为了实现它们的潜力，我们需要建立最佳的多层结构来支持合成的反铁磁天微子，这些天微子体积小，流动性强，并沿着电流驱动的方向移动。我们需要找到一种可靠的成核方法，能够以受控的方式产生合成的反铁磁天子，以便进一步研究。我们需要知道如何通过平衡两个分量天子上的马格努斯力来使合成的反铁磁天子直接响应于自旋电流驱动，从而将天米子的霍尔角减小到零。最后，我们需要学习如何利用预期的拓扑衰减抑制来移动合成的反铁磁天子，其速度比传统天子的速度高得多，尺寸也小得多。在这个项目中，我们将制备支持合成反铁磁性天米子的手性磁性多层膜，成像天米子结构，并制造纳米级器件，在其中我们可以测量电流驱动的天米子动力学。我们将把我们的专业知识与合成反铁磁性多层膜结合起来，并证明我们有能力在界面上诱导Dzyaloshinskii-Moriya相互作用，将两个极性和手性相反的耦合天米子结合成可以在室温下稳定的合成反铁磁性天米子，并使用最先进的显微镜技术在场下对它们的结构和运动进行成像。接下来，我们将研究由于施加包括磁场或电流脉冲在内的刺激，人工合成的反铁磁天微子在随机发生和故意引入的缺陷处的成核。然后，我们将准备Skyrmion跑道，利用这个优化的多层堆栈中的电流驱动力矩，可以沿着这些跑道推进合成的反铁磁性Skyrmion，并成像中等电流密度下的Skyrmion运动，以便测量Skyrmion霍尔角并找出它为零时的条件。我们将继续增加电流密度，利用在合成反铁磁中耦合的拓扑缺陷之间产生的拓扑阻尼的抑制来寻求高速天米子的运动。我们将获得的结果不仅将通过揭示这种新型材料组合提供的可能性而导致高影响力的出版物和会议报告，而且还将在基于合成反铁磁天子子的自旋电子学领域为技术应用开发潜在的有价值的技术。

In this project we will stabilise small circular magnetic domains called skyrmions in chiral synthetic antiferromagnetic multilayers and study their current-driven dynamics. The project is based on two recent breakthroughs by our groups: our being able to stabilise skyrmions as a topologically protected structure (making them resistant to annihilation) in a suitably designed single chiral perpendicularly magnetised layer, and being able to move coupled topological defects (domain walls) at low current density in a simple in-plane magnetised synthetic antiferromagnet.Whilst conventional skyrmions are interesting candidates for a variety of novel information storage and processing devices that offer the prospect of very low power operation, they are expected to move slowly at small sizes due to topological damping and are diverted at an angle to their current drive direction by the Magnus forces that lead to a skyrmion Hall effect. To realise their potential, we need to establish the optimal multilayer structure to support synthetic antiferromagnetic skyrmions that are small, highly mobile, and move in the direction of an electrical current drive. We need to find a reliable nucleation method to that can create synthetic antiferromagnetic skyrmions in a controlled manner for further study. We need to know how make synthetic antiferromagnetic skyrmions respond directly to spin current drives by balancing the Magnus forces on the two component skyrmions to reduce the skyrmion Hall angle to zero. Finally, we need to learn how to exploit the expected suppression of topological damping in order to move the synthetic antiferromagnetic skyrmions move at velocities far higher, and at smaller sizes, than for conventional skyrmions. In this project we will prepare chiral magnetic multilayers that support synthetic antiferromagnetic skyrmions, image the skyrmion structures, and fabricate nanoscale devices in which we can measure current-driven skyrmion dynamics. We will combine our expertise with synthetic antiferromagnet multilayers with our proven ability to induce strong Dzyaloshinskii-Moriya interactions at interfaces to combine two coupled skyrmions with opposite polarity and chirality into a synthetic antiferromagnetic skyrmion that can be stabilised at room temperature, with their structure and motion under field imaged using state-of-the-art microscopy techniques. Next, we will study the nucleation of synthetic antiferromagnetic skyrmions at randomly occurring and deliberately introduced defects due to the application of stimuli including pulses of magnetic field or electrical current. We will then prepare skyrmion racetracks along which synthetic antiferromagnetic skyrmions can be propelled using current-driven torques from this optimised multilayer stack and image the skyrmion motion at moderate current densities in order to measure the skyrmion Hall angle and find the conditions when it is zero. We will go on to increase the current densities to seek high velocity skyrmion motion exploiting the suppression of topological damping that arises between coupled topological defects in synthetic antiferromagnets.The results we shall obtain will not only lead to high impact publications and conference presentations by shedding light on the possibilities offered by this novel combination of materials, but also develop potentially valuable knowhow in the field of spintronics based on synthetic antiferromagnetic skyrmions for technological applications.