Open Access

Daniel Metternich

• Magnetic thin films with perpendicular anisotropy are widely studied as they exhibit a broad spectrum of magnetic domain textures and compelling properties for future spintronic and neuromorphic computing applications. A key factor influencing domain behavior is the chirality of the surrounding domain walls, which governs their stability, mobility, and topology.Since early research into bubble domain materials in the 1960s, the properties and dynamics of domain walls have been studied continuously.Although it has long been known that pinning at material defects affects domain walls, the ability to study these interactions at the microscopic level has been limited.Steady technological advancement in ultrafast excitation techniques and x-ray imaging now enables new insights into these nanometer-scale magnetic textures. In this thesis, we examine how material defects and inhomogeneities affect the statics and dynamics of chiral and topological spin structures. We focus on three caseMagnetic thin films with perpendicular anisotropy are widely studied as they exhibit a broad spectrum of magnetic domain textures and compelling properties for future spintronic and neuromorphic computing applications. A key factor influencing domain behavior is the chirality of the surrounding domain walls, which governs their stability, mobility, and topology.Since early research into bubble domain materials in the 1960s, the properties and dynamics of domain walls have been studied continuously.Although it has long been known that pinning at material defects affects domain walls, the ability to study these interactions at the microscopic level has been limited.Steady technological advancement in ultrafast excitation techniques and x-ray imaging now enables new insights into these nanometer-scale magnetic textures. In this thesis, we examine how material defects and inhomogeneities affect the statics and dynamics of chiral and topological spin structures. We focus on three case studies, each targeting a distinct aspect of defect-induced magnetic behavior. For each project, we develop and deploy x-ray imaging and characterization techniques based on circular and linear magnetic x-ray dichroism contrast to resolve features spatially on the nanometer scale and with picosecond time resolution, supported by complementary measurements and modeling. First, we investigate the impact of lateral inhomogeneities on the static domain wall chirality in DyCo thin films. Our vector imaging technique reveals strong lateral chirality variations imprinted by the local material properties, which appear to be influenced by the initial as-grown domain state. Second, we utilize vector x-ray imaging to analyze domain wall defects in all-optically switched GdFe samples. Analysis of the defect density allows insights into the switching and nucleation dynamics of the domain wall itself. We uncover that post-nucleation domain wall propagation through an inhomogeneous material matrix is the dominant nucleation channel for domain wall defects. Third, we study the laser-induced nucleation and localization of magnetic skyrmions in a patterned Co/Pt multilayer. We consolidate the homogeneous, exchange-driven nucleation of skyrmions after laser excitation with the observation that local anisotropy variations can induce a deterministic localization: We find that the localization is determined by purely local stability characteristics that induce skyrmion decay or proliferation. Our findings collectively demonstrate how lateral material inhomogeneities govern both equilibrium configurations and dynamic processes of chiral and topological magnetic textures, offering key insights for future device design and fundamental studies of magnetic matter.…