  Magnetic droplet solitons were first predicted to occur in materials with
uniaxial magnetic anisotropy due to a long-range attractive interaction between
elementary magnetic excitations, magnons. A non-equilibrium magnon population
provided by a spin-polarized current in nanocontacts enables their creation and
there is now clear experimental evidence for their formation, including direct
images obtained with scanning x-ray transmission microscopy. Interest in
magnetic droplets is associated with their unique magnetic dynamics that can
lead to new types of high frequency nanometer scale oscillators of interest for
information processing, including in neuromorphic computing. However, there are
no direct measurements of the time required to nucleate droplet solitons or
their lifetime---experiments to date only probe their steady-state
characteristics, their response to dc spin currents. Here we determine the
timescales for droplet annihilation and generation using current pulses.
Annihilation occurs in a few nanoseconds while generation can take several
nanoseconds to a microsecond depending on the pulse amplitude. Micromagnetic
simulations show that there is an incubation time for droplet generation that
depends sensitively on the initial magnetic state of the nanocontact. An
understanding of these processes is essential to utilizing the unique
characteristics of magnetic droplet solitons oscillators, including their high
frequency, tunable and hysteretic response.
