  A magnetic vortex has attracted significant attention since it is a
topologically stable magnetic structure in a soft magnetic nanodisk. Many
studies have been devoted to understanding the nature of magnetic vortex in
isolated systems. Here we show a new aspect of a magnetic vortex the dynamics
of which strongly affects the magnetic structures of environment. We exploit a
nanodot of an exchange-coupled bilayer with a soft magnetic Ni81Fe19
(permalloy; Py) having a magnetic vortex and a perpendicularly magnetized
L10-FePt exhibiting a large switching field (Hsw). The vortex dynamics with
azimuthal spin waves makes the excess energy accumulate in the Py, which
triggers the reversed-domain nucleation in the L10-FePt at a low magnetic
field. Our results shed light on the non-local mechanism of a reversed-domain
nucleation, and provide with a route for efficient Hsw reduction that is needed
for ultralow-power spintronic devices.
