Magnetic bubbles and stripe domains in nanostructured FePd elements

The analysis of the magnetization process in rectangular thin dots exhibiting a canted anisotropy is reported. The studied dots with quality factor Q≈0.4 are large enough to sustain at least a bi-domain pattern at the remnant state. The various magnetic patterns observed in modeling hysteresis with the external field applied along one of the edges of the dot, moving from one saturated state to the opposite one, are described according to the length of the dots. The facts that the easy axis is tilted with respect to the normal of the dot surface, associated with the limited size of the dots, impose a double flux-closure scheme for the magnetization distribution. The reversal occurs via bubbles nucleation inside the dots followed by the transition to a stripe pattern. Furthermore, it is shown in the description of hysteresis loop that the full magnetization reversal needs successive injections of two sets of Bloch-points. Special attention is paid to topological problems associated with the injection and expulsion of these singularities.