The Role of Novel Magnetic Interactions in Surface-Supported Magnetic Nanodot Assemblies

The manipulation of matter at the atomic scales facilitates understanding of the fundamental properties of magnetism and opens the possibility of designing systems with novel magnetic properties with limitless industrial applications. This thesis seeks to identify nano-scale magnetic coupling mechanisms in nanostructures assemblies and to better understand different magnetic phases and the associated transitions. This was accomplished through the study of three prototype systems: Fe nanodots of controlled size and density on single crystal substrates of nonmagnetic metals, fractal – dimensional Fe on Cu(111), and FeGe nanowires on Ge(111). The first system shows the presence of a novel magnetic coupling in the nanodot arrays through the surface substrate, allowing the design of a Fe nanodot/Cu multilayer system with tunable magnetism in bulk and on surface. The second system shows a magnetic phase transition with unusual interface magnetism. The third shows how magnetic nature of FeGe (antiferromagnetic) can be shifted in nanostructures to ferromagnet under compressive strain. In all the topics, a new magnetic characteristic has been observed and discussed in details. The novel methods used to fabricate and control nanostructures will have a great impact in studying the emerging physical phenomena of magnetic materials in reduced dimensionality.