Part-spherical nanodots

We have seen above that the magnetisation reversal in the half-sphere occurs via vortex nucleation similar to the mechanism in the flat cylinder shown in section 3.4. We have shown in section 3.5 that a full sphere reverses via a different mechanism. From this it can be concluded that for some height $h > d/2$ of a part-sphere a transition between the two reversal mechanisms takes place.

These results are also relevant to the experimentally manufactured nanodots because the amount of material that is deposited through the self-assembly method described in section 5.1.3 can be varied to grow spheres of heights $h \leq d$.

We calculate numerically the magnetisation reversal of soft part-spherical particles. The observed reversal mechanisms range from single domain reversal at small radii, to vortex movement in shallow systems at larger radii and vortex core reversal at larger heights as observed in spheres.

In this section we study the behaviour of the new class of part-spherical structures and compute a magnetic reversal phase diagram as a function of diameter and height.