Frederik Wegelin

Magnetization Dynamics in Spin Valves: a Study Using Time Resolved Photo?emission Electron Microscopy in Combination with X?ray Circular Dichroism (Tr-peem-xmcd) Frederik Wegelin

Key technology applications like magnetoresistive sensors or the Magnetic Random Access Memory (MRAM) require reproducible magnetic switching mechanisms. i.e. predefined remanent states. At the same time advanced magnetic recording schemes push the magnetic switching time into the gyromagnetic regime. Objects of study in this study are antiparallel pinned synthetic spin valves as they are extensively used as read heads in today?s magnetic storage devices. Results are reported of element specific Time Resolved Photo?Emission Electron Microscopy (TR?PEEM) to image the magnetization dynamics of the free layer alone via X? ray Circular Dichroism (XMCD). The observation of magnetic switching processes in the gigahertz range became possible due to the joined effort of producing ultra?short X?ray pulses at BESSY II and optimizing the wave guide design of the samples for high frequency electromagnetic excitation. It could be shown that the magnetization dynamics of the free layer of a GMR spin valve stack deviates significantly from a simple phase coherent rotation.