Propagating two-dimensional magnetic droplets

Hoefer, Mark; Sommacal, Matteo

doi:10.1016/j.physd.2012.02.003

Cited by 24 publications

(46 citation statements)

References 32 publications

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“…The supersonic transition in the moving frame is estimated by use of a numerical method described elsewhere [51]. A moving, perpendicular, localized, weak magnetic field spot with velocityV is used to perturb a homogeneous state in the bias field h 0 =n.…”

Section: Galilean Invariance Is Recovered Near Vacuum With Dispersionmentioning

confidence: 99%

Breaking of Galilean Invariance in the Hydrodynamic Formulation of Ferromagnetic Thin Films

2017

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Microwave magnetodynamics in ferromagnets are often studied in the small-amplitude or weakly nonlinear regime corresponding to modulations of a well-defined magnetic state. However, strongly nonlinear regimes, where the aforementioned approximations are not applicable, have become experimentally accessible. By re-interpreting the governing Landau-Lifshitz equation of motion, we derive an exact set of equations of dispersive hydrodynamic form that are amenable to analytical study even when full nonlinearity and exchange dispersion are included. The resulting equations are shown to, in general, break Galilean invariance. A magnetic Mach number is obtained as a function of static and moving reference frames. The simplest class of solutions are termed uniform hydrodynamic states (UHSs), which exhibit fluid-like behavior including laminar flow at subsonic speeds and the formation of a Mach cone and wave-fronts at supersonic speeds. A regime of modulational instability is also possible, where the UHS is violently unstable. The hydrodynamic interpretation opens up novel possibilities in magnetic research.

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Section: Galilean Invariance Is Recovered Near Vacuum With Dispersionmentioning

confidence: 99%

Breaking of Galilean Invariance in the Hydrodynamic Formulation of Ferromagnetic Thin Films

2017

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“…3(a)]. Additionally, in this regime we also observe a well-defined Mach In the moving reference frame, we use a pseudo-spectral method 46 to solve the nondimensionalized LL equation, Eq. (1).…”

Section: Numerical Resultsmentioning

confidence: 96%

Vortex-antivortex proliferation from an obstacle in thin film ferromagnets

Iacocca¹,

Hoefer²

2017

Phys. Rev. B

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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 vortexantivortex complexes using this approach enables the study of their interactions and effects on the stability of spin-density waves.1 arXiv:1610.08940v3 [cond-mat.mes-hall]

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“…The motion of a dynamic particle-like droplet can also transform the energy stored in the precessional motion into the effective kinetic energy of the translational motion [36][37][38]. Similar to Newton's law ݀ܺ ሬሬሬሬሬ⃗ ‫ݐ݀/‬ = ܸ ሬ⃗ , the droplet continues to move with a constant velocity due to its inertia.…”

Section: A Droplet In a Quasi-lossless Mediummentioning

confidence: 99%

“…4a). This is based on the fact that the droplets with higher frequencies should feature smaller effective masses and, consequently, higher propagation speeds; see Ref [36][37][38]. The spatial distribution of the eigenmodes of the propagating droplet is of special interest for applications in information transport via magnons, which are presented in Fig.…”

Section: A Droplet In a Quasi-lossless Mediummentioning

confidence: 99%

Propagating Magnetic Droplet Solitons as Moveable Nanoscale Spin-Wave Sources with Tunable Direction of Emission

et al. 2020

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Magnetic droplets are strongly nonlinear and localized spin-wave solitons that can be formed in current-driven nanocontacts. Here, we propose a simple way to launch droplets in an inhomogeneous nanoscopic waveguide. We use the drift motion of a droplet and show that in a system with broken translational symmetry, the droplet acquires a linear momentum and propagates. We find that the droplet velocity can be tuned via the strength of the break in symmetry and the size of the nanocontact. In addition, we demonstrate that the launched droplet can propagate up to several micrometers in a realistic system with reasonable damping. Finally, we demonstrate how an annihilating droplet delivers its momentum to a highly nonreciprocal spin-wave burst with a tunable wave vector with nanometer wavelengths. Such a propagating droplet can be used as a moveable spin-wave source in nanoscale magnonic networks. The presented method enables full control of the spin-wave emission direction, which can largely extend the freedom to design integrated magnonic circuits with a single spin-wave source.

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Propagating two-dimensional magnetic droplets

Cited by 24 publications

References 32 publications

Breaking of Galilean Invariance in the Hydrodynamic Formulation of Ferromagnetic Thin Films

Breaking of Galilean Invariance in the Hydrodynamic Formulation of Ferromagnetic Thin Films

Vortex-antivortex proliferation from an obstacle in thin film ferromagnets

Propagating Magnetic Droplet Solitons as Moveable Nanoscale Spin-Wave Sources with Tunable Direction of Emission

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