Stroboscopic domain imaging by Kerr microscopy

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The remagnetization process of structured magnetic film systems, as they are currently developed for magnetic memory and sensor applications, proceeds by complicated domain states for elements in the micrometer size range and beyond. The topic to be addressed in the project is the fast reversal of magnetization in single and multilayer film elements with lateral dimensions of a few micrometers up to some ten micrometers upon the application of pulsed magnetic fields. The dynamic development of domains will be directly observed by time-resolved widefield Kerr microscopy with a time resolution of about 100 picoseconds at highest lateral resolution possible in optics. An ultrafast CCD camera together with a constant light source will be used for imaging. Due to the weak Kerr contrast, an accumulation of images in a stroboscopic averaging technique is required to get sufficient signal-to-noise ratios. Therefore the method is restricted to repetitive magnetization modes. Our microscope combines the advantage of digitally enhanced Kerr microscopy with the possibility of high-speed observation.