Excitations with negative dispersion in a spin vortex

Buess, Matthias; Knowles, Tuomas P. J.; Höllinger, Rainer; Haug, Tobias; Krey, U.; Weiss, Dieter; Pescia, D.; Scheinfein, M. R.; Back, Christian

doi:10.1103/physrevb.71.104415

Cited by 92 publications

(81 citation statements)

References 29 publications

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“…8 Dipolar spin-wave modes have frequencies in the GHz range and describe dynamic excitations of the planar part of the vortex structure. 9,10 Two mode numbers n and m indicate the number of nodes in radial and azimuthal directions of the mode profile and the sign of m defines the rotational sense of the mode (m < 0: clockwise, and m > 0: counter clockwise). Due to their symmetry, dipolar spin-wave modes with azimuthal mode numbers jmj ¼ 1 can be efficiently excited by magnetic in-plane fields.…”

Section: Introductionmentioning

confidence: 99%

Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

Noske

Stoll

Fähnle

et al. 2016

Journal of Applied Physics

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Scanning transmission x-ray microscopy is employed to investigate experimentally the reversal of the magnetic vortex core polarity in cylindrical Ni81Fe19 nanodisks triggered by two orthogonal monopolar magnetic field pulses with peak amplitude B0, pulse length τ=60 ps, and delay time Δt in the range from −400 ps to +400 ps between the two pulses. The two pulses are oriented in-plane in the x- and y-directions. We have experimentally studied vortex core reversal as a function of B0 and Δt. The resulting phase diagram shows large regions of unidirectional vortex core switching where the switching threshold is modulated due to resonant amplification of azimuthal spin waves. The switching behavior changes dramatically depending on whether the first pulse is applied in the x- or the y-direction. This asymmetry can be reproduced by three-dimensional micromagnetic simulations but not by two-dimensional simulations. This behavior demonstrates that in contrast to the previous experiments on vortex core reversal, the three-dimensionality in the dynamics is essential here.

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Section: Introductionmentioning

confidence: 99%

Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

Noske

Stoll

Fähnle

et al. 2016

Journal of Applied Physics

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“…Among the magnetic elements which have been investigated in detail, one may find squares, [1][2][3] rings, 4,5 stripes, [6][7][8] and circular disks. [9][10][11] In some recent papers, the attempts to manipulate the structure of spin-wave modes in confined magnetic elements by modification of the elements' physical properties have been reported. [10][11][12] A particular attention has been paid to diskshaped elements due to their simplicity.…”

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confidence: 99%

Mode degeneracy due to vortex core removal in magnetic disks

et al. 2007

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The mode spectrum of micrometer-sized ferromagnetic Permalloy disks, exhibiting a vortex ground state, is investigated by means of time-resolved scanning Kerr microscopy. The temporal evolution of the magnetization is probed after application of a fast in-plane field pulse. The lowest order azimuthal mode, a mode with only one diametric node, splits into a doublet as the disk diameter decreases. Theoretical models show that this splitting is a consequence of the interaction of the mode with the gyrotropic motion of the vortex core. Our experiments and micromagnetic simulations confirm that by removing the vortex core from the disk, the mode splitting vanishes. DOI: 10.1103/PhysRevB.76.014416 PACS number͑s͒: 75.75.ϩa, 75.40.Gb The spectra and spatial structure of spin-wave modes in small ferromagnetic elements characterized by an almost flux-closed ͑stray field free͒ magnetization state have been thoroughly investigated in recent years. Among the magnetic elements which have been investigated in detail, one may find squares, 1-3 rings, 4,5 stripes, 6-8 and circular disks. [9][10][11] In some recent papers, the attempts to manipulate the structure of spin-wave modes in confined magnetic elements by modification of the elements' physical properties have been reported. [10][11][12] A particular attention has been paid to diskshaped elements due to their simplicity. The response of these elements to the external excitation with pulsed and continuous magnetic fields has been studied both experimentally and theoretically. 10,11,13,14 In general, two types of dynamic excitations can be found in these cylindrically shaped elements that exist in the vortex ground state. The first type, known as a gyrotropic mode, 1,15,16 is the oscillatory motion of the vortex core itself. In the absence of an external bias field, the vortex core is located at the center of the disk. After the application of an in-plane magnetic field pulse, the vortex is displaced from the center. While the system relaxes toward its equilibrium state, the vortex gyrates around the disk center. With the disk diameters in the micrometer range, the frequencies of this gyrotropic mode lie in the subgigahertz range. In the experiments described below, the accessible time range was about 3.4 ns and, therefore, the gyrotropic mode could not be observed.The second type of modes, known as magnetostatic modes, is the relatively high-frequency ͑several gigahertz͒ spin-wave excitations. These modes in the cylindrical geometry might have circular nodal lines ͑characterized by the radial index n͒ and diametric nodal lines ͑characterized by the azimuthal index m͒. In a recent paper, 9 it has been shown that for disks having a large aspect ratio of diameter ͑e.g., several micrometers͒ to thickness ͑e.g., 20 nm͒, the experimentally measured frequencies of these excitations can be well described by considering only the dipolar energy and pinned boundary conditions.When the disk diameter is decreased, the influence of the vortex core and of the exchange interaction mus...

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“…The quasi-eigenmode E 1 at 7.3 GHz shows one maximum and the quasi-eigenmode E 2 at 6.6 GHz shows three maxima in each half of the ring. The fact that higher azimuthal quasi-eigenmodes in rings and disks have lower frequencies due to their backward volume mode character is well known and was reported previously [9,16].…”

Section: Methodsmentioning

confidence: 81%

Dissipation characteristics of quantized spin waves in nano-scaled magnetic ring structures

Schultheiß¹,

Sandweg²,

Obry³

et al. 2008

J. Phys. D: Appl. Phys.

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Abstract. The spatial profiles and the dissipation characteristics of spin-wave quasieigenmodes are investigated in small magnetic Ni 81 Fe 19 ring structures using Brillouin light scattering microscopy. It is found, that the decay constant of a mode decreases with increasing mode frequency. Indications for a contribution of three-magnon processes to the dissipation of higher-order spin-wave quasi-eigenmodes are found.arXiv:0804.2200v1 [cond-mat.mtrl-sci]

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Excitations with negative dispersion in a spin vortex

Cited by 92 publications

References 29 publications

Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

Mode degeneracy due to vortex core removal in magnetic disks

Dissipation characteristics of quantized spin waves in nano-scaled magnetic ring structures

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