Topological spin structures beyond skyrmions from first-principles

磁性skyrmions -稳定的，本地化的自旋结构-持有未来的自旋电子应用的巨大希望。它们在自旋电子器件中潜在应用的一个关键限制是Skyrmion Hall效应，该效应导致Skyrmion从电流方向偏转。因此，像跑道一样的几何形状的skyrmions向轨道的边缘移动，导致它们的湮灭，从而丢失信息。就使用skyrmion作为信息载体而言，仅通过skyrmion的存在（=1）或不存在（=0）来存储位也是阻碍。非常希望具有另一种可以充当零位值的亚稳自旋结构。因此，研究一种以上亚稳自旋结构可以共存的系统，不仅从基本观点来看是有趣的。一个动物园的拓扑自旋结构以外的skyrmions，例如反skyrmions，反铁磁skyrmions或高阶skyrmions，已被预测。这些自旋结构表现出有前途的性能，最显着的改进控制由于没有Skyrmion霍尔效应。然而，大多数的理论研究是基于自旋模型与任意的磁相互作用参数和这些自旋结构的稳定性仍然在很大程度上未被探索。特别是，塌缩机制是未知的，保护它们免受湮灭的能垒也没有计算出来。最终，需要确定这种拓扑自旋结构的寿命，这是一个非常具有挑战性的任务，由于可能的过渡路径的复杂性，不仅需要计算能垒，而且需要计算阿克里先乌斯定律的尝试频率。此外，还迫切需要将第一性原理计算与原子自旋模拟相结合，以探索Skyrmions之外的拓扑自旋结构的性质，并预测有前途的材料系统，以便发现和潜在应用。我们将使用密度泛函理论（DFT），在第一性原理电子结构理论的基础上开发和应用原子自旋模拟程序预测新的磁性界面，表现出超越skyrmions的拓扑自旋结构。使用尖端的原子自旋模拟-在该项目中进一步开发，以便它们可以应用于Skyrmions之外的拓扑自旋结构-我们将探索它们的性质，例如崩溃和创建机制，它们的稳定性和它们在有限温度下的寿命基于DFT参数所有磁相互作用。系统的选择是这样的，他们是实验可行的，这可能会允许发现拓扑自旋结构超越skyrmions和实验研究其属性。这将是在自旋电子器件中使用这种自旋结构的重要一步。

Magnetic skyrmions – stable, localized spin structures – hold great promise for future spintronic applications. A key limitation of their potential application in spintronic devices is the skyrmion Hall effect which leads to a deflection of skyrmions from the direction of the electric current. Therefore, skyrmions in a race-track like geometry move towards the edge of the track resulting in their annihilation and thus the loss of information. In terms of using skyrmions as information carriers it is also hindering that the bit can only be stored by the presence (=1) or absence (=0) of the skyrmion. It is highly desirable to have another kind of metastable spin structure which can act as the zero bit value. Therefore, it is not only interesting from the fundamental point of view to study systems in which more than one type of metastable spin structure can co-exist. A zoo of topological spin structures beyond skyrmions, e.g. antiskyrmions, antiferromagnetic skyrmions or higher-order skyrmions, has been predicted. These spin structures exhibit promising properties most prominently improved control due to the absence of the skyrmion Hall effect. However, most of the theoretical studies are based on spin models with arbitrary magnetic interaction parameters and the stability of these spin structures remains largely unexplored. In particular, the collapse mechanisms are unknown and the energy barriers protecting them against annihilation have not been calculated. Ultimately, the lifetime of such topological spin structures needs to be determined which is a very challenging task due to the complexity of possible transition paths and the need to calculate not only energy barriers but also the attempt frequencies of the Arrhenius law. There is also a strong need for first-principles calculations in combination with atomistic spin simulations to explore the properties of topological spin structures beyond skyrmions and to predict promising material systems for their discovery and for potential applications.In this project, we will develop and apply an atomistic spin simulations code built on first-principles electronic structure theory using density functional theory (DFT) to predict novel magnetic interfaces exhibiting topological spin structures beyond skyrmions. Using cutting-edge atomistic spin simulations – which are further developed within this project such that they can be applied to topological spin structures beyond skyrmions – we will explore their properties such as collapse and creation mechanisms, their stability and their lifetime at finite temperature based on DFT parameters for all magnetic interactions. The choice of systems is such that they are experimentally feasible which may allow to discover topological spin structures beyond skyrmions and to experimentally investigate their properties. This will be an important step towards using such spin structures in spintronic devices.