  We present a comprehensive investigation of the size-dependent switching
characteristics and spin wave modes of FePt nanoelements. Curved nanomagnets
("caps") are compared to flat disks of identical diameter and volume over a
size range of 100 to 300nm. Quasi-static magnetization reversal analysis using
first-order reversal curves (FORC) shows that spherical caps have lower vortex
nucleation and annihilation fields than the flat disks. As the element diameter
decreases, the reversal mechanism in the caps crosses over sooner to coherent
rotation than in the disks. The magnetization dynamics are studied using
optically induced small angle precession and reveal a strong size dependence
that differs for the two shapes. Flat disks exhibit well-known center and edge
modes at all sizes, but as the diameter of the caps increases from 100 to 300
nm, additional oscillation modes appear in agreement with dynamic micromagnetic
simulations. In addition, we show that the three-dimensional curvature of the
cap causes a much greater sensitivity to the applied field angle which provides
an additional way for controlling the ultrafast response of nanomagnetic
elements.
