Regensburg 2002 – wissenschaftliches Programm

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SYRE: Rastersonden- und Elektronenmikroskopie an Domänenstrukturen

SYRE III: HV III

SYRE III.1: Hauptvortrag

Dienstag, 12. März 2002, 10:30–11:00, H11

SEMPA studies of ferromagnetic domains at surfaces — •Gerold Steierl, G. Liu, D. Iorgov, and J. Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, Halle (Saale), Germany

Scanning Electron Microscopy with Polarization Analysis (SEMPA) is a well-established technique for the observation of ferromagnetic domains with high resolution and outstanding surface sensitivity. Up to recently, it was a drawback of the technique, that the samples could not be exposed to strong magnetic fields for data acquisition. We report on an advanced setup that circumvents this experimental limitation and therefore allows for the direct observation of magnetization reversal processes. Several applications of this technique towards the investigation of ultra-thin films and magnetic microstructures are discussed.
As exemplary ultra-thin film system we report on the magnetization reversal in Fe films grown on Cu(100) with thicknesses up to 30 monolayer (ML). Fe films with a thickness beyond 10 ML reveal densely spaced as-grown domains. These are created during growth when the film transforms from the fcc to the bcc lattice. For these thicknesses the magnetization reversal process is discussed. The results directly show that high resolution in-field SEMPA measurements are possible in external magnetic fields of up to 30 mT.
The switching behavior of Permalloy microstructures (Ni80Fe20, 50 nm thick) is reported for lateral dimensions between 2 - 10 µm. The switching process of rectangles from the diamond to the S-state is observed in detail. The S-state is found to be rather in-stable in large rectangles. Frequently, decays towards the diamond state occur. The saturation process of Permalloy disks starting from the vortex state are reported. Apart from the motion of the vortex, also the fine structures of the domain patterns are observed.