  Magnetic droplets are dissipative magnetodynamical solitons that can form
under current driven nanocontacts in magnetic layers with large perpendicular
magnetic anisotropy. Here, we extend the original droplet theory by studying
the impact of the dipolar interactions on the dynamics of droplet solitons. By
varying the thickness of the free layer of a spin torque nano-oscillator, we
systematically tune the internal field of the free layer to investigate the
dynamics of droplet solitons. Our numerical results show that increasing the
free layer thickness increases the droplet threshold current, decreases the
droplet frequency and diameter, enlarges the current hysteresis and also
modifies the structure of the droplet. The Oersted field of the current breaks
the phase coherency and deteriorates the stability of the droplet in free
layers with larger thicknesses. Moreover, our findings show a simple relation
to determine the impact of the free layer thickness on the droplet nucleation
boundaries. Our study presents the missing brick on the physics behind magnetic
droplet solitons, and further illustrates that magnetic droplets in thinner
layers possess more promising characteristics for spintronic applications and
enable devices with higher speed of operation.
