Vortex-antivortex proliferation from an obstacle in thin film ferromagnets

Abstract

Magnetization dynamics in thin film ferromagnets can be studied using a dispersive hydrodynamic formulation. The equations describing the magnetodynamics map to a compressible fluid with broken Galilean invariance parametrized by the longitudinal spin density and a magnetic analog of the fluid velocity that define spin-density waves. A direct consequence of these equations is the determination of a magnetic Mach number. Micromagnetic simulations reveal nucleation of nonlinear structures from an impenetrable object realized by an applied magnetic field spot or a defect. In this work, micromagnetic simulations demonstrate vortex-antivortex pair nucleation from an obstacle. Their interaction establishes either ordered or irregular vortex-antivortex complexes. Furthermore, when the magnetic Mach number exceeds unity (supersonic flow), a Mach cone and periodic wavefronts are observed, which can be well-described by solutions of the steady, linearized equations. These results are reminiscent of theoretical and experimental observations in Bose-Einstein condensates, and further supports the analogy between the magnetodynamics of a thin film ferromagnet and compressible fluids. The nucleation of nonlinear structures and vortex-antivortex complexes using this approach enables the study of their interactions and effects on the stability of spin-density waves.

23 pages, 7 figures

References in corpus (12)

• Dispersive shock waves and modulation theory
• Theory for a dissipative droplet soliton excited by a spin torque nanocontact
• Oblique dark solitons in supersonic flow of a Bose-Einstein condensate
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• Breaking of Galilean invariance in the hydrodynamic formulation of ferromagnetic thin films
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Cited by in corpus (10)

• Skyrmion production on demand by homogeneous DC currents
• Solution of the Riemann problem for polarization waves in a two-component Bose-Einstein condensate
• Symmetry-broken dissipative exchange flows in thin-film ferromagnets with in-plane anisotropy
• Perspectives on spin hydrodynamics in ferromagnetic materials
• Hydrodynamic description of long-distance spin transport through noncollinear magnetization states: the role of dispersion, nonlinearity, and damping
• Magnonic Band Structure Established by Chiral Spin-Density Waves in Thin Film Ferromagnets
• Spin-injection-generated shock waves and solitons in a ferromagnetic thin film: the spin piston problem
• Controllable vortex shedding from dissipative exchange flows in ferromagnetic channels
• Contact solitons as spin pistons in one-dimensional ferromagnetic channels
• Dynamics of metastable contact soliton dissipative exchange flows in one-dimensional ferromagnetic channels