Helimagnons and Skyrmion Dynamics in Cu2OSeO3 and Fe/Gd Multilayers Explored by Brillouin Light Scattering and X-ray Microscopy

Spin dynamics in skyrmion hosting materials provide novel functionality in magnonics because of the formation of a novel magnon band structure and the nanoscale sizes of magnetic skyrmions. In this thesis, we explore the spin dynamics in the chiral magnet Cu2OSeO3 locally utilizing the scanning micro-focus Brillouin light scattering (BLS) technique at cryogenic temperature. Taking advantage of the high sensitivity and spatial resolution of BLS, we resolved the one-to-one correspondence between different non-collinear phases, such as helical, chiral soliton, conical and skyrmion phases, in a chiral magnet and their collective spin excitations. We show that the continuous-wave laser in BLS enables the stabilization of metastable phases and creation of skyrmion tracks surrounded by the conical phase. The high sensitivity of BLS allows us to deepen the understanding of coexisting phases in the chiral magnet. The results pave the way for the design of further magnonic devices based on chiral magnets. Furthermore, we explore dipolar skyrmions and domain walls in amorphous Fe/Gd multilayers employing scanning transmission x-ray microscopy. We demonstrate the formation of stripe and square lattices of domains by integrating one-dimensional and two-dimensional nanomagnet arrays, respectively. Dynamics of domain walls, multi-domain boundaries and skyrmions were captured with pump-probe spectroscopy. In a skyrmion pair, a magnon wavelength down to 239 nm at 0.33 GHz was observed and compared to the electromagnetic wave whose wavelength is 0.9 m at the same frequency. The extreme wavelength conversion underlines the potential of skyrmion hosting materials concerning miniaturization of information technology and microwave devices