Magnetic ground states and higher-order interactions beyond monolayers

磁性基态和单层之外的高阶相互作用

• 批准号: 418425860
• 负责人: Dr. Kirsten von Bergmann
• 金额: --
• 依托单位: Institut für Nanostruktur- und Festkörperphysik (INF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/418425860?language=en
• 关键词: Magnetic; ground; states; higher; order

The magnetic ground state of a material is governed by the magnetic interactions between atomic magnetic moments. The standard spin model includes the Heisenberg pairwise exchange interaction, the Dzyaloshinskii-Moriya interaction (DMI), and the magnetocrystalline anisotropy. However, higher-order exchange interactions involving exchange between more than two sites can play an important role and lead to intriguing three-dimensional spin configurations in magnetic ground states. In addition, topological spin structures such as skyrmions or antiskyrmions can be stabilized by higher-order terms even in the absence of DMI. Recently, new higher-order terms such as the topological-chiral and chiral-multi spin interactions have been proposed albeit their relevance has not yet been verified experimentally. Experimental and theoretical studies have so far focused almost exclusively on magnetic systems of single atomic layers. For transport applications, e.g. in multilayers, however, beyond-monolayer systems are relevant. A realistic atomistic spin model for such systems with magnetic bi- or trilayers is missing but indispensable for further studies regarding predictions for materials with tailored properties, such as magnetic ground state, phase transitions, thermodynamical properties, existence and stability of topological spin structures, and spin dynamics. In this project we aim to obtain insight into the magnetic and electronic properties of model-type systems of magnetic films beyond monolayers on single crystal surfaces. We will combine density functional theory (DFT), atomistic spin simulations, and experiments with spin-polarized scanning tunneling microscopy (STM) to unravel which kind of atomic- and nano-scale magnetic ground states can occur. Several magnetic bi- and trilayer of 3d transition metals on metallic surfaces of different symmetries will be studied and we expect to discover novel types of spin structures. To understand the microscopic origin of complex spin structures in such magnetic films we will develop an atomistic spin model which includes different types of intra- and interlayer interactions, using parameters obtained from DFT. To date, there is basically no understanding concerning the role of interlayer higher-order interactions in beyond-monolayer films. We will reveal which interactions are possible and what their role for the magnetic ground state formation is. We will also study the mutual interactions between the symmetry of the magnetic texture and the electronic properties, relevant for the transport properties, by comparison of DFT with STM and spectroscopy measurement. We believe that a joint experimental and theoretical study is fundamental for the understanding of the role of different interactions onto the magnetic ground states and the impact of magnetism on the electronic states in systems beyond monolayers and that our project will lead to the discovery of novel spin states and stabilization mechanisms.

材料的磁性基态由原子磁矩之间的磁相互作用控制。标准自旋模型包括海森堡成对交换相互作用、Dzyaloshinskii-Moriya 相互作用 (DMI) 和磁晶各向异性。然而，涉及两个以上位点之间交换的高阶交换相互作用可以发挥重要作用，并导致磁性基态中有趣的三维自旋构型。此外，即使在没有 DMI 的情况下，拓扑自旋结构（例如斯格明子或反斯格明子）也可以通过高阶项来稳定。最近，提出了新的高阶术语，例如拓扑手性和手性多自旋相互作用，尽管它们的相关性尚未得到实验验证。迄今为止，实验和理论研究几乎完全集中在单原子层的磁系统上。对于运输应用，例如然而，在多层中，超单层系统是相关的。这种具有磁性双层或三层的系统缺少真实的原子自旋模型，但对于进一步研究具有定制特性的材料（例如磁性基态、相变、热力学特性、拓扑自旋结构的存在和稳定性以及自旋动力学）的预测是必不可少的。在这个项目中，我们的目标是深入了解单晶表面单层磁性薄膜模型类型系统的磁性和电子特性。我们将结合密度泛函理论（DFT）、原子自旋模拟和自旋极化扫描隧道显微镜（STM）实验来揭示可能出现哪种原子和纳米尺度的磁性基态。我们将研究不同对称性金属表面上的几种磁性双层和三层三维过渡金属，我们期望发现新型的自旋结构。为了了解此类磁性薄膜中复杂自旋结构的微观起源，我们将使用从 DFT 获得的参数开发一个原子自旋模型，其中包括不同类型的层内和层间相互作用。迄今为止，人们对层间高阶相互作用在超单层薄膜中的作用基本上还没有了解。我们将揭示哪些相互作用是可能的，以及它们对磁性基态形成的作用是什么。我们还将通过 DFT 与 STM 和光谱测量的比较，研究磁性纹理的对称性和与输运特性相关的电子特性之间的相互作用。我们相信，联合实验和理论研究对于理解不同相互作用对磁性基态的作用以及磁性对单层系统以外的电子态的影响至关重要，并且我们的项目将导致新的自旋态和稳定机制的发现。