  Ferromagnetic channels subject to spin injection at one extremum sustain
long-range coherent textures that carry spin currents known as dissipative
exchange flows (DEFs). In the weak injection regime, spin currents carried by
DEFs decay algebraically and extend through the length of the channel, a regime
known as spin superfluidity. Similar to fluids, these structures are prone to
phase-slips that manifest as vortex-antivortex pairs. Here, we numerically
study vortex shedding from DEFs excited in a magnetic nanowire with a physical
obstacle. Using micromagnetic simulations, we find regimes of laminar flow and
vortex shedding as a function of obstacle position tunable by the and spin
injection sign and magnitude. Vortex-antivortex pairs translate forward (VF
regime) or backward (VB regime) with respect to the detector's extremum,
resulting in well-defined spectral features. Qualitatively similar results are
obtained when temperature, anisotropy, and weak non-local dipole fields are
included in the simulations. These results provide clear features associated
with DEFs that may be detected experimentally in devices with nominally
identical boundary conditions. Furthermore, our results suggest that obstacles
can be considered as DEF control gates, opening an avenue to manipulate DEFs
via physical defects.

Mesoscale and Nanoscale Physics