"Magnetization dynamic in prototype microstructures investigated with ultimate time and space resolution and element selectivity"
Magnetization dynamic in prototype microstructures investigated with ultimate time and space resolution and element selectivity
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In this thesis the dynamic magnetic contrast observed with scanning transmission X-ray microscopy ferromagnetic resonance (STXM-FMR) is investigated. By using a time resolved detection scheme in transversal X-ray detected ferromagnetic resonance (XFMR) it is possible to investigate the dynamic behavior of magnetic micro-structures with element selectivity. The space resolution of nominally 35 nm due to the zone plate of the STXM-FMR was conrmed using a nano-particle sample. A time resolution of down to 17.4 ps corresponding to a excitation frequency of the FMR of f MW = 9.64 GHz can be achieved at the Stanford Synchrotron Radiation Lightsource (SSRL). Dierent methods to separate the background contribution from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) are presented. The opening angle of the FMR precession as well as the relative phase between the microwave excitation and the X-ray pulses can be quantied using the corresponding evaluation method. Control experiments using homogeneous and inhomogeneous magnetic excitations are used to verify that the dynamic magnetic contrast behaves like the classical XMCD eect under reversal of the X-ray photon helicity. Homogeneous as well as inhomogeneous FMR excitation modes can be analysed in greater detail using X-ray transmission proles obtained from the individual phases used to measure the precession of the magnetization during FMR excitation. Visualizing the dynamic magnetic contrast for non-homogeneous excited magnetic samples, travelling spin waves have been observed in two magnetic micro-stripes, perpendicular to each other. Analysing the spin wave movement enables to estimate that the spin wave velocity is of the order of 42.5 km/s .