Thesis defense of Philipp Weinert

Spintronics offers huge potential for data storage and processing and, thus, for overcoming the challenges arising from the ever-increasing demands in the field of electronics. To fully utilize this potential in real-world applications, appropriate materials are required. Graphene-ferromagnetic interfaces show great promise in this context. Combining graphene with a ferromagnet, such as cobalt, results in a system with many advantageous effects, such as Dzyaloshinskii-Moriya interaction (DMI). These effects allow for the formation of useful spin structures with high stability. Furthermore, such structures can also be induced in cobalt by combining it with a heavy non-magnetic metal such as platinum. In this study, the magnetic interlayer coupling and domain structure of ultra-thin ferromagnetic cobalt (Co) layers embedded between a graphene ( G) layer and a platinum (Pt) layer on a silicon carbide (SiC) substrate (G/Co/Pt on SiC) were investigated. The (6V3 x 6vf3) R30°-reconstruction was prepared on SiC and served as a precursor for graphene. lt was prepared using two techniques, namely confinement controlled sublimation (CCS) and polymer assisted sublimation growth (PASG). Consequently, the sample properties varied slightly. Following this, the metal layers were prepared by intercalation. Experimentally, a combination of x-ray photoemission electron microscopy (X-PEEM) with x-ray magnetic circular dichroism (XMCD) was carried out at the Co L-edge to study the system's magnetic structure. Furthermore, structural and chemical properties of the system were investigated using low-energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS). In-situ LEED patterns revealed the crystalline structure of each layer within the system. Moreover, XPS confirmed the presence of quasi-freestanding graphene and the absence of cobalt silicide. These characteristics of a clean and homogeneous Co-layer provide an excellent foundation for magnetic features to form. The magnetic structure of all samples exhibited numerous spin vortices and anti-vortices. In spintronics, these can be used as data carriers. The general magnetic structure of the material is heavily influenced by the preparation method. Different aspects were identified, which enhance or impede the formation of vortices.