Thermally excited Skyrmions: from individual to collective dynamics

热激发斯格明子：从个体到集体动力学

• 批准号: 403502522
• 负责人: Professor Dr. Mathias Kläui
• 金额: --
• 依托单位: Arbeitsgruppe Theorie magnetischer Materialien
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/403502522?language=en
• 关键词: Thermally; excited; Skyrmions; individual; collective

In this project we will use a combined theoretical and experimental approach to understand the statics and dynamics of thermally excited skyrmions. We will go beyond currently studied ferromagnetic systems and explore systems with multiple magnetic sublattices that are coupled antiparallelly, including synthetic as well as intrinsic ferrimagnetic and antiferromagnetic skyrmions with complex properties resulting from their multiple sub-lattices.The first step is to ascertain the thermal dynamics of individual skyrmions based on our joint work on ferromagnetic skyrmions and first observations of diffusion in ferrimagnetic and synthetic antiferromagnetic skyrmion systems. With exciting predictions of strongly enhanced diffusive dynamics for low net magnetic moments, this bodes well for diffusion-based non-conventional computing. Thus, we will probe the skyrmion diffusion from the regime of large ferromagnetic moments down to zero net moment where the sub-lattices fully compensate each other. We will vary the net magnetic moment in ferrimagnets by tuning the temperature and in synthetic antiferromagnets by choosing appropriate thicknesses of the layers. In the second step, we will probe the collective dynamics of skyrmion ensembles that can form different phases, such as the hexatic phase and topological phase transitions unique to 2D systems. We start by statistically analysing the skyrmion positions in a sample, which allows us to quantify the potential landscape that the skyrmions feel, including probing predictions of enhanced attempt frequencies for antiferromagnetic skyrmions and the skyrmion interactions that govern the resulting phase transitions. The phases and phase transitions will then be probed by analysing their local orientational order parameter in comparison to numerical simulations. Finally, we will use the unique dynamic tunability of skyrmion sizes and shapes to study the dynamics of the phase formation and phase transition. By abruptly varying the skyrmion size and shape, we can study the time-resolved equilibration process to identify key processes driving phase transitions.We will implement the work using a range of selected experimental magnetic techniques that operate at variable temperature in combinations with variable applied magnetic fields. We will use primarily real-time magnetic microscopy for direct imaging complemented by magnetic scattering techniques. Theoretically we use a unique combination of numerical simulation techniques that allow us to span from the electronic to the mesoscopic scale. From atomistic spin simulations we will ascertain the intrinsic thermal dynamics of antiferromagnetic skyrmions, which then allows us to extract realistic parameters to model experimentally accessible skyrmion sizes using micromagnetic approaches, finally enabling molecular dynamics simulations of as large ensembles of skyrmions as necessary to model phases and phase transitions.

在这个项目中，我们将使用理论和实验相结合的方法来理解热激发skyrmions的静态和动态。我们将超越目前研究的铁磁系统，探索具有多个磁子晶格的系统，这些磁子晶格是反铁磁耦合的，包括合成的以及固有的亚铁磁和反铁磁skyrmions，其具有复杂的性质，第一步是根据我们对铁磁skyrmions的联合工作和亚铁磁和铁磁中扩散的首次观察，确定单个skyrmions的热动力学。合成反铁磁Skyrmion系统。随着令人兴奋的预测，强烈增强的扩散动力学低净磁矩，这预示着良好的扩散为基础的非传统计算。因此，我们将探讨skyrmion扩散从制度的大铁磁矩下降到零净矩的子晶格完全相互补偿。我们将通过调节温度来改变亚铁磁体的净磁矩，通过选择适当的层厚度来改变合成反铁磁体的净磁矩。在第二步中，我们将探索可以形成不同相的skyrmion系综的集体动力学，例如2D系统特有的六角相和拓扑相变。我们首先统计分析样品中的skyrmion位置，这使我们能够量化skyrmion感觉到的潜在景观，包括探测预测反铁磁skyrmion的增强尝试频率和管理由此产生的相变的skyrmion相互作用。相和相变，然后将探讨通过分析它们的本地取向序参数相比，数值模拟。最后，我们将利用skyrmion尺寸和形状的独特动态可调性来研究相形成和相变的动力学。通过突然改变skyrmion的大小和形状，我们可以研究时间分辨的平衡过程，以确定驱动相变的关键过程。我们将使用一系列选定的实验磁性技术来实现这项工作，这些技术在可变温度下与可变的外加磁场相结合。我们将主要使用实时磁显微镜直接成像辅以磁散射技术。理论上，我们使用一个独特的数值模拟技术的组合，使我们能够跨越从电子到介观尺度。从原子自旋模拟，我们将确定反铁磁skyrmion的内在热动力学，然后使我们能够提取现实的参数来模拟实验上可访问的skyrmion大小使用微磁方法，最后使分子动力学模拟的大合奏skyrmion作为必要的模型相位和相变。