Magnetic states and magnetization process in Ni-Fe sub-micron cup-shaped dots

We have investigated the magnetic states and magnetization process in sub-micron cup-shaped magnetic dots that consist of magnetic circular layers and magnetic ring layers. Ni-20at% Fe cup-shaped dots with an outer diameter-of 500nm have vortical magnetic configurations at zero magnetic fields to reduce magnetostatic energy, while Co-17 at% Pt cup-shaped dots show the unidirectional magnetic configurations. Results of micromagnetics simulation show that the vortex-nucleation field of the N-20 at% Fe cup-shaped dots is positive, however, it is lower than that of the ordinary ring dots because the magnetic circular layers of the cup-shaped dots introduce. vortex cores into themselves.