Controllable vortex shedding from dissipative exchange flows in ferromagnetic channels

TL;DR

This paper investigates vortex shedding phenomena in ferromagnetic channels with dissipative exchange flows, demonstrating controllable vortex regimes through obstacle positioning and spin injection parameters, with implications for experimental detection and device manipulation.

Contribution

It introduces a numerical study of vortex shedding in DEFs, revealing controllable regimes and potential for DEF manipulation using physical obstacles.

Findings

Vortex shedding regimes depend on obstacle position and spin injection parameters.

Spectral features correlate with vortex-antivortex pair dynamics.

Temperature and anisotropy minimally affect vortex shedding behavior.

Abstract

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.