Effective spin meron pairs in ferromagnetic multilayer elements

Topological spin textures, such as vortices or skyrmions, are attracting significant attention because of both their intriguing fundamental properties and their promising applicability in memory devices or spin torque oscillators. A particular topological texture that was theoretically predicted is the two-dimensional hedgehog state, also known as a ’spin meron’. It had been unclear, however, whether this kind of highly divergent magnetization structure may exist in real systems. Only recently, evidence for the occurrence of meron-like pair states was reported for the case of trilayer elements consisting of two ferromagnetic layers and a non-ferromagnetic interlayer.On this background we present a direct proof for the existence of meron-like states in trilayer elements via direct magnetic imaging. We also show that in the presence of biquadratic interlayer exchange coupling, such meron-like pair states may even represent the magnetic ground state of the system. Interestingly, the highly divergent magnetization distribution induces an additional, three-dimensional torus vortex that in-turn causes a symmetry break for the allowed topological pair configurations.In the second part of our presentation we will address the dynamic properties of vertically coupled topological spin textures, where the focus will be on spin wave emission processes in such systems.