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Vortex-antivortex proliferation from an obstacle in thin film ferromagnets

Ezio Iacocca (Institutionen för fysik, Teoretisk fysik (Chalmers)) ; M. A. Hoefer
Physical Review B: covering condensed matter and materials physics (2469-9950). Vol. 95 (2017), 13,
[Artikel, refereegranskad vetenskaplig]

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 spindensity 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 support 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.

Nyckelord: magnetic droplet solitons, dynamics, skyrmions, nucleation, motion, waves

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Denna post skapades 2017-05-17. Senast ändrad 2017-06-09.
CPL Pubid: 249387


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