Hamburg 2001 – scientific programme

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AM: Magnetismus

AM 17: Mikromagnetismus II (Dots, Partikel)

AM 17.3: Talk

Friday, March 30, 2001, 10:45–11:00, S 5.4

Imaging the switching process of magnetic microstructures by using SEMPA — •G Steierl, G Liu, and J Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle

We report on experimental advances in Scanning Electron Microscopy with Polarization Analysis (SEMPA) that allow the observation of switching processes in magnetic microstructures. In our approach, the microstructures can be subjected to magnetic fields of up to about 1kOe during imaging. This is achieved by using a modified electron optics that ends towards the sample with a magnetic gap, that is positioned close to sample surface. During imaging, primary and secondary electrons travel through the magnetic field. To suppress the precession of the secondary electron spin-polarization, the secondary electrons are accelerated by using a strong electric field between the gap and the sample surface. It is shown by our measurements and by ray-tracing simulation that the effects of the magnetic field on both electron beams are negligible. As an exemplary study, we report on the switching behavior of Permalloy microstructures. These were produced in a variety of shapes (rectangles, disks) and sizes by electron beam lithography and lift off. Depending on size and shape of the element different domain instabilities are observed. The interaction of vortices with boundaries is found to be of crucial importance to explain the switching process.