  The nucleation of superconductivity in a superconducting disk with a Co/Pt
magnetic triangle was studied. We demonstrate that when the applied magnetic
field is parallel to the magnetization of the triangle, the giant vortex state
of vorticity three splits into three individual F0-vortices, due to a
pronounced influence of the C3 symmetry of the magnetic triangle. As a result
of a strong pinning of the three vortices by the triangle, their configuration
remains stable in a broad range of applied magnetic fields. For sufficiently
high fields, F0-vortices merge and the nucleation occurs through the giant
vortex state. The theoretical analysis of this novel reentrant behaviour at the
phase boundary, obtained within the Ginzburg - Landau formalism, is in
excellent agreement with the experimental data.
