Giant moving vortex mass in thick magnetic nanodots

Guslienko, K. Yu.; Kakazei, G. N.; Ding, J.; Liu, X. M.; Adeyeye, A. O.

doi:10.1038/srep13881

Cited by 42 publications

(42 citation statements)

References 33 publications

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“…This hybridization leads to a frequency splitting of the azimuthal dipolar spin waves that agrees well with experimental results [15][16][17]. In addition, the hybridization of G 0 , G 1 and dipolar spin waves leads to a reduction of the frequency of the gyrotropic mode for increasing disk thickness [26]. This reduced frequency is in better agreement to experimental results [19] compared to previous analytical theory [2,7].…”

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confidence: 81%

“…This hybridization leads to the frequency splitting of the dipolar modes with different values of the azimuthal index m [6,15], which was briefly discussed in the introduction. It also leads to the renormalization and a decrease of the fundamental gyromode frequency [1,19,26] compared to the "unhybridized" case [2] (see orange curve at large thickness in Figs. 2 and 3 in Ref.…”

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confidence: 99%

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Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures: Hybridization of Flexure Gyromodes with Spin Waves

et al. 2016

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Three-dimensional linear spin-wave eigenmodes of a vortex-state Permalloy disk are studied by micromagnetic simulations based on the Landau-Lifshitz-Gilbert equation. The simulations confirm that the increase of the disk thickness leads to the appearance of additional exchange-dominated so-called gyrotropic flexure modes having nodes along the disk thickness, and eigenfrequencies that decrease when the thickness is increased. We observe the formation of a gap in the mode spectrum caused by the hybridization of the first flexure mode with one of the azimuthal spin-wave modes of the disk. A qualitative change of the transverse profile of this azimuthal mode is found, demonstrating that in a thick vortex-state disk the influence of the "transverse" and the "azimuthal" coordinates cannot be separated. The threedimensional character of the eigenmodes is essential to explain the recently observed asymmetries in an experimentally obtained phase diagram of vortex-core reversal in relatively thick Permalloy disks. DOI: 10.1103/PhysRevLett.117.037208 The study of spin-wave (SW) excitations in micro-and nanosized magnetic elements is one of the most important topics in modern magnetism. The dynamic spin-wave eigenmodes of finite-size magnetic elements not only determine the high-frequency properties of these elements, but also provide valuable information about remagnetization processes in nanomagnetic objects, as the change of the magnetic ground state of an element is, usually, happening through the softening of one of the SW eigenmodes of this element. When the ground state of magnetization in a magnetic element is spatially uniform the spatial distribution of the spin-wave excitations can, usually, be factorized, and represented as a product of three functions of three independent coordinates (separation ansatz).The situation becomes much more complicated in the case when the magnetic element is thick, so that it has to be treated as three-dimensional (3D), and the magnetization ground state of the element is spatially nonuniform. In that case the possibilities of traditional analytic methods are limited; however, the essential information about SW excitations can be obtained from micromagnetic simulations. As it will be shown below, in a 3D spatially nonuniform case the dependence of the spin-wave mode profile on some of the spatial coordinates gets mixed, and the above discussed separation ansatz traditionally used in the analytic theory does not work anymore.A relatively simple example of a magnetic element having spatially nonuniform ground state of static magnetization is a vortex-state magnetic disk [1][2][3]. In a cylindrical nanodisk with thickness h of a few tens of nanometers and diameter 2R of typically several hundred nanometers the magnetic ground state is a vortex. There the magnetization curls in the plane of the disk with a clockwise (CW) or counterclockwise (CCW) circulation. At the center of the disk in an area with a typical diameter of 10 to 20 nm the magnetization turns out of the plane [3] form...

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Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures: Hybridization of Flexure Gyromodes with Spin Waves

et al. 2016

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“…More precisely, moving skyrmion cannot be considered as an absolutely rigid object, its dynamical profile is deformed that can be represented as a hybridization with azimuthal spin waves excited over the skyrmion background 37 and resulting in a finite skyrmion inertia term in the Thiele equation of motion. The low frequency gyrotropic eigenmodes are closely related to nonzero skyrmion mass 38,40 . Recently two gyrotropic modes in the CoB/Pt circular dots modes were simulated and measured by X-ray imaging technique 38 .…”

Section: Resultsmentioning

confidence: 99%

“…However, the second higher frequency gyrotropic mode can be interpreted as azimuthal spin wave 37,39,40 , and there is only one gyrotropic mode in the dot spin excitation spectrum. Nevertheless, the skyrmions can have a considerable mass accounting for their magnetic energy change increasing skyrmion velocity.…”

Section: Resultsmentioning

confidence: 99%

Gyrotropic Skyrmion Modes in Ultrathin Magnetic Circular Dots

Guslienko

Gareeva

2017

IEEE Magn. Lett.

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We calculate low-frequency gyrotropic spin excitation modes of the skyrmion ground state ultrathin cylindrical magnetic dots. The skyrmion is assumed to be stabilized at room temperature and zero external magnetic field due to an interplay of the isotropic and Dzyaloshinskii-Moriya exchange interactions, perpendicular magnetic anisotropy and magnetostatic interaction. We consider Bloch-and Neel-type magnetic skyrmions and assume that the dot magnetization does not depend on the thickness coordinate. The skyrmion gyrotropic frequencies are calculated in GHz range as a function of the skyrmion equilibrium radius, dot radius and the dot magnetic parameters. Recent experiments on magnetic skyrmion gyrotropic dynamics in nanodots are discussed.

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“…3,4 For this, the static 5 and dynamic [6][7][8] behavior of magnetic vortices have been studied extensively. More fundamental aspects, like a magnetic structure of a vortex core or microscopic mechanisms of vortex nucleation/annihilation, have also attracted a lot of attention and have been investigated using a variety of tools.…”

Section: Introductionmentioning

confidence: 99%

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

Lapa

Ding

Phatak

et al. 2017

Journal of Applied Physics

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The topological nature of magnetic-vortex state gives rise to peculiar magnetization reversal observed in magnetic microdisks.Interestingly, magnetostatic and exchange energies which drive this reversal can be effectively controlled in artificial ferrimagnet heterostructures composed of rare-earth and transition metals. [Py(t)/Gd(t)]25 (t=1 or 2 nm) superlattices demonstrate a pronounced change of the magnetization and exchange stiffness in a 10-300 K temperature range as well as very small magnetic anisotropy. Due to these properties, the magnetization of cylindrical microdisks composed of these artificial ferrimagnets can be transformed from the vortex to uniformly-magnetized states in a permanent magnetic field by changing the temperature. We explored the behavior of magnetization in 1.5-µm [Py(t)/Gd(t)]25 (t=1 or 2 nm) disks at different temperatures and magnetic fields and observed that due to the energy barrier separating vortex and uniformly-magnetized states, the vortex nucleation and annihilation occur at different temperatures. This causes the temperature dependences of the Py/Gd disks magnetization to demonstrate unique hysteretic behavior in a narrow temperature range. It was discovered that for the [Py(2 nm)/Gd(2 nm)]25 microdisks the vortex can be metastable at a certain temperature range.

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Giant moving vortex mass in thick magnetic nanodots

Cited by 42 publications

References 33 publications

Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures: Hybridization of Flexure Gyromodes with Spin Waves

Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures: Hybridization of Flexure Gyromodes with Spin Waves

Gyrotropic Skyrmion Modes in Ultrathin Magnetic Circular Dots

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

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