PhD Thesis

Institut für Angewandte Physik, Uni Hamburg

I did my PhD in Hamburg at the institute for Applied Physics about magnetic nanoparticles and finished the PhD in Novemebr 2011. The title of the thesis is

Maskentechnik zur Erzeugung epitaktischer Nanostrukturen und Modifikation der magnetischen Anisotropie von ultradünnen Co/Au(111)-Filmen durch Ionenätzen

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In this thesis ultrathin epitaxial Co/Au(111)-nanostructures and especially their magnetic anisotropic behaviour are examined.

I develop a method to produce epitaxial nanostructures using a mask technique. The masks are cut of a silicon nitride membrane by focussed ion beam and mounted on a support which can be placed in ultrahigh vacuum on a single-crystal sample. By thermal evaporation, the cobalt is deposited on the substrate and epitaxial nanostructures grow. The masks can be reused several times and it is thus possible to generate structures with the same lateral dimensions but different layer thicknesses. The so prepared structures are studied using the magneto-optical Kerr effect with a special focus on their magnetic anisotropy. This thesis describes the design, construction and the assembly of a ultra high vacuum apparatus as well as its application to the afore mentioned processes.

Furthermore, the magnetic anisotropy of extended Co/Au(111) films, which were removed by ion bombardment, is investigated. The bombardment changes the surface of the epitaxial films and reduces the surface anisotropy. Hence, the existing perpendicular magnetization direction of ultrathin films is lost. At low energies, however, it is possible to erode the films so that the perpendicular anisotropy is not completely lost, but in turn leads to a new perpendicular magnetization. I investigate this behaviour and discuss a model of explanation. As a result, the experiments are able to provide separate measures of the surface anisotropy and the Co-Au interface anisotropy.

Publication

The PhD thesis is published at the Staats- und Universitätsbibliothek Hamburg.
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