Magnetization dynamics of Landau structures: tuning the response of mesoscopic magnetic objects using defects

Magnetic vortex cores are interacting with and can be annihilated by artificial defects, such as holes. We report the imaging of the magnetic excitation spectrum in presence of holes, fabricated by focussed ion beam milling, in the magnetic domains, domain walls, and the center of Landau structures by means of x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). Due to the very high lateral and temporal resolution the magnetization dynamics, which is characteristic for the vortex-hole interaction, is investigated in detail. We find that the vortex as well as domain walls can be trapped by small holes. As a consequence the frequency vortex gyrotropic motion is enhanced with a significant lower amplitude in case of non centric holes in domain walls. Non centric holes in domains lead to no frequency shift, but a higher amplitude of the vortex gyration due to attractive vortex-hole interaction. The experimental results are compared to micromagnetic simulations.