Magnonic Phenomena in Low-Dimensional Magnetic Insulators: Mechanisms and Applications

Abstract

Most logical devices today are electronic, which means a technology based on the charge property of electron currents. A fundamental disadvantage of a charge current is the loss of energy due to Joule heating. There is however a second fundamental property of particles, the magnetic property or spin, which can be used as an information carrier. By using only magnetic waves in an electrical insulator, the Joule heating can be avoided. Some magnetic waves are furthermore much faster than electronic currents. This reduced energy consumption and the increase in processing speed motivate our research. However, many fundamental characteristics of magnetic waves are not yet known. Thus, supplementing the technological development, we still need fundamental research to explore and understand basic properties. This PhD thesis aims to study transport of magnetic waves in ferromagnetic (FM) and antiferromagnetic (AFM) insulators in order to understand their fundamental behavior. Using mainly computational methods, we access experimentally and analytically inaccessible regions of time- and space resolution, complex coupling and perturbation, non-linear interactions and finite-temperature effects. We focus on two types of materials systems: twodimensional (2D) van der Waals (vdW) materials and AFM thin films like hematite. Our work can be grouped into two categories. First, we solve open questions concerning magnon transport. In hematite we reproduce the experimentally observed Hanle effect and explain it based on magnonic beating. In the vdW magnet CrCl3 we report how strain modifies the magnon diffusion length. For the vdW magnet CrI3 we present experimentally accessible observables that will allow the unique identification of the underlying spin interactions in this controversial material. Second, we propose new phenomena and approaches. By the example of CrI3 we present a computational tool that utilizes the intrinsic spin Nernst effect to probe magnon topology. Furthermore, using a hematite-like thin film we demonstrate an AFM neuron based on magnon-induced texture motion. Finally, we discuss an ongoing project on the generation of an AFM magnon condensate.