Development and applications of mesoscopic hall microprobes
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Novoselov, Konstantin S.
[S.l. : s.n.]
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This thesis is devoted to the further development of the local Hall magnetometery technique, and its application for studying ferromagnetic domain wall propagation on the sub-atomic scale. First the ballistic electron transport in a strong, non-uniform magnetic field is discussed. Than a possible increase of working temperature range of submicron Hall probes up to room temperatures is investigated. And in the last part is an insight into the mechanism of ferromagnetic domain walls motion measured with ballistic Hall magnetometery is given. Ballistic Hall magnetometery is widely used for studying magnetization properties of superconductive and ferromagnetic materials. It was shown both experimentally and theoretically, that the Hall response of a ballistic Hall probe is proportional to the average magnetic field over the central area of the Hall probe. However, as with any technique, Ballistic Hall magnetometery has certain limitations. In first two chapters of the thesis I consider two cases of strong, non-uniform magnetic field within the Hall probe, where the Hall response is no longer proportional to the flux. Further I apply ballistic Hall micromagnetometry to study sub-micron movements of domain walls in thin films of YIG. The small domain wall jumps are found to correspond exactly to the lattice periodicity in garnet crystals. This was attributed to manifestation of the Peierls potential. These experiments allowed me to investigate inter- and intra-Peierls valley dynamics of the domain wall. The experimental results can be well described within the framework of the model of kink nucleation and propagation through the domain wall. However, some features, like slow dynamic of the kinks are still not completely understood.
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