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

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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.