Spin texture in magnetic thin films.

Magnetism of thin films is a core research topic in solid state physics. During the past ten years the focus of attention has shifted towards the nanoscale. This regime has become accessible due to the progress in deposition techniques as well as in lithographic patterning techniques and in the sensitivity of advanced characterization techniques. Apart from the fundamental interest in magnetic interactions at the nanometer scale, this research field also gets significant interest from the applications side, in particular in relation to magnetic data storage. Although some manifestations of magnetic interactions like ferromagnetism, antiferromagnetism, helical and cycloidal order have been known for a long time, nature still has some surprises in store: Just over two years ago the first experimental evidence was found for the socalled ‘skyrmion’ state i.e. the spontaneous formation of vortex-like spin structures while applying a modest magnetic field. These skyrmions typically organize in a hexagonal arrangement, comparable to the vortex state in a type-II superconductor. As this is still a very recent finding, many questions remain unsolved, e.g. in what magnetic field and temperature range do skyrmions appear, what is the interaction between skyrmions in thin films, how are skyrmions related to the atomic structure and morphology of the film, how do they interact wit h a transport current? In this project we will prepare relevant samples using either solid phase epitaxy, reactive deposition epitaxy or co-deposition, techniques which we have been refining over the past two decades. We will study the skyrmions using scanning tunneling microscopy and spectroscopy (to image the skyrmions and their arrangement) and apply the powerful x-ray beams of a synchrotron to investigate the magnetic spin structure of skyrmions. With this project we aim at delivering a significant contribution to the deeper understanding of this novel and exciting magnetic phenomenon.