Carlos A. F. Vaz
Cavendish Laboratory, PCS, University of Cambridge
Photo-emission electron microscopy (PEEM) is a high resolution, element specific imaging technique, particularly well suited to the study of the equilibrium magnetic configurations and domain wall dynamics of microscopic and submicroscopic magnetic elements. We illustrate some of the capabilities of PEEM with examples from our work on magnetic ring and disc elements, conducted at the SLS (Villegen) and at ELETTRA (Trieste). Namely, we show how the geometric parameters of ring elements determine the exact equilibrium spin configuration of the domain walls of rings in the `onion state', and we show how such behaviour can be understood as the result of the competition between the exchange and magnetostatic energy terms. Also, from the study of the magnetic states of micrometer sized discs we show that several equilibrium states may be stabilised at remanence by defects or attained in the nucleation process following the removal of the applied magnetic field. A final example will be drawn from our studies of the displacement of domain walls by electric currents. By directly imaging the detailed spin structure and/or the position of domains walls following the application of a pulsed current, we are able to study the effect of spin currents on the wall velocities and on the domain wall structure itself.
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