Magnetization reversal via bloch points nucleation in nanowires and dots: a micromagnetic study

Micromagnetic studies of the reversal of stripe domains in elements of different geometries are reported. Various 2D and 3D codes are used in order to allow comparison between an infinite slab, nanowires and dots. Starting from a saturated state the establishment of stripe domains through the sample is first studied. Contrary to the thin film case, the nucleation of this pattern is not uniform and is very different to the geometry of a wire or an isolated dot. Special attention is paid to the reversal of the core of the vortex (the remnants of inner walls between up and down domains) which requires the insertion of point singularities called Bloch points (BP) either at surfaces or created in a pair depending on the length allowed for the stripe in the corresponding element. The magnetization distribution around the core of the various BP is described in detail as well as the key characteristics of their motion. Finally, some experiments are suggested predicting the behaviour of stripe domains under an applied field. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005