Magnetization dynamics of confined ferromagnetic systems

The aim of this thesis is to shed light into the resonantly excited spin wave spectrum of confined ferromagnetic systems. When exposing a magnetic sample to an ac magnetic field with appropriate frequency, the magnetization starts to precess around its equilibrium position at a characteristic resonance frequency. In the present work the dynamic response of the magnetization was probed by employing both inductive as well as spatially resolved optical techniques. In doing so, sinusoidal excitation is emphasized. However, the results obtained from the novel frequency domain techniques are compared to well established techniques in the time (applying a field pulse) and field domain (conventional ferromagnetic resonance).\\ First the dynamic response of a well characterized ultrathin Fe film on GaAs(001) substrate was investigated by means of the novel inductive vector network analyzer ferromagnetic resonance technique. In order to test the reliability of this novel technique, the obtained results are compared in terms of resonance frequency and magnetic damping to pulsed inductive microwave magnetometry, time resolved scanning Kerr microscopy, and conventional ferromagnetic resonance. In addition, all techniques are compare regarding their signal to noise ratios. \\ In the second experimental part of the thesis the absorption spectrum of permalloy disks with 200~nm diameter demonstrates the potential of the network analyzer ferromagnetic resonance technique for the investigation of nano-structured magnetic elements having nonuniform magnetization configuration. The results are compared to data from Brillouin light scattering and numerical calculations.\\ On this basis larger disks with 4 micrometer diameter were investigated in order to reveal the modal pattern. Spatially resolved optical techniques allowed to investigate the disks both in their remanent vortex state and as a function of an external in-plane magnetic field.\\ Finally, the modal pattern of ferromagnetic ring structures is presented and discussed. Again, inductive and spatially resolved optical techniques disclose the resonant mode spectrum and pattern in the remanent states and as a function of an externally applied in-plane field.\\ Micromagnetic simulations were employed to back up the experimental results