Electronic theory of magnetic domain walls and magnetic field switching in transition-metal nanowires: Confinement, local environment and temperature effects

磁区和磁区壁是任何铁磁材料的重要特征。了解磁性纳米结构中DW的性质对于技术应用是至关重要的，特别是在存储器和自旋电子器件中，DW的存在与存储的信息本身是无法分离的。本项目的目标是从量子力学理论上描述过渡金属磁性纳米线(NWS)中的量子散射物理以及与之相关的磁化重取向转变。人们关注的焦点是DWS的形成能量和大小，壁内磁序的性质，两壁之间的相互作用，磁场的影响和磁化转换的机制。这些性质作为宽度、结构、组成和温度的函数进行了研究，目的是将它们与特定于导线的电子结构以及与环境相关的各向异性能量和局域矩之间的有效交换耦合联系起来。详细研究了线-衬底相互作用的影响，特别是对于具有更强的自旋-轨道耦合的高极化衬底(例如，Pd，Pt和Rh)。除了对超薄纳米粒子中离散波结构的量子力学理解之外，这项工作还应该在电子学理论和唯象微磁方法之间提供联系，这应该导致基于显微镜的一维纳米结构的多尺度建模。

Magnetic domains and domain walls (DWs) are an important feature of any ferromagnetic material. Understanding the properties of DWs in magnetic nanostructures is crucial to technological applications, particularly in memory and spin-electronic devices where the presence of a DW cannot be disjoined from the stored information itself. The goal of this project is the quantum-mechanical theoretical description of the physics of DWs in transition-metal magnetic nanowires (NWs) and of the associated magnetization reorientation transitions. The focus of attention are the formation energy and size of the DWs, the nature of the magnetic order within the wall, the interactions between two walls, the effect of magnetic fields and the mechanisms for magnetization switching. These properties are investigated as a function of width, structure, composition and temperature with the aim of correlating them with the wire-specific electronic structure and with the environment-dependent anisotropy energies and effective exchange couplings between local moments. The effects of wire-substrate interactions are investigated in detail, in particular for highly-polarizable substrates with stronger spin-orbit couplings (e.g., Pd, Pt and Rh). Besides the quantum mechanical understanding of DWs in ultrathin NWs, this work should provide a link between electronic theory and phenomenological micromagnetic approaches that should lead to a microscopically-based multiscale modeling of 1D nanostructures.