Vortex Core-Driven Magnetization Dynamics

Choe, Sug–Bong; Acremann, Yves; Schöll, A.; Bauer, Andreas; Doran, Andrew; Stöhr, J.; Padmore, H. A.

doi:10.1126/science.1095068

Cited by 600 publications

(512 citation statements)

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“…With two possible orientations of c and p, four different ground states of a magnetic vortex can occur 7,8 . The magnetic vortex structure constitutes a fascinating topological structure for fundamental studies of nanoscale spin behaviour and offers great potential as a novel concept in data storage technologies [9][10][11][12][13][14][15] . A priori, one would expect the energy of the four states to be degenerate.…”

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confidence: 99%

“…A non-degeneracy would not only constitute an unconventional physical phenomenon at the nanoscale but could also lead to potentially interesting applications of magnetic vortices with regard to magnetic sensor or logic elements 16,17 . Owing to the lack of experimental techniques enabling simultaneous imaging of in-plane (c) and out-of-plane (p) magnetic components in nanopatterned structures, most of the experiments on magnetic vortices reported so far have focussed on either the chirality or polarity 9,15 . Therefore, the degeneracy of a magnetic vortex has not been experimentally verified to date.…”

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Symmetry breaking in the formation of magnetic vortex states in a permalloy nanodisk

et al. 2012

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The magnetic vortex in nanopatterned elements is currently attracting enormous interest. A priori, one would assume that the formation of magnetic vortex states should exhibit a perfect symmetry, because the magnetic vortex has four degenerate states. Here we show the first direct observation of an asymmetric phenomenon in the formation process of vortex states in a permalloy nanodisk using high-resolution full-field magnetic transmission soft X-ray microscopy. micromagnetic simulations confirm that the intrinsic Dzyaloshinskii-moriya interaction, which arises from the spin-orbit coupling due to the lack of inversion symmetry near the disk surface, as well as surface-related extrinsic factors, is decisive for the asymmetric formation of vortex states.

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Symmetry breaking in the formation of magnetic vortex states in a permalloy nanodisk

et al. 2012

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“…Magnetism on the nanometer scale and its spin dynamics on a nsec to fsec time scale is currently a scientfically highly attractive topic [1,2] since it addresses both fundamental magnetic lengh scales such as magnetic exchange lengths in the sub-10nm range [3] and interesting time scales of magnetism such as precessional and relaxation phenomena, domain wall and vortex dynamics [4][5][6]. The fundamental time scale in magnetism is given by the time required to transfer energy and momentum from the electronic into the spin system [7], which aims e.g.…”

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Exploring nanomagnetism with soft X-ray microscopy

et al. 2007

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Magnetic soft X-ray microscopy images magnetism in nanoscale systems with a spatial resolution down to 15nm provided by state-of-the-art Fresnel zone plate optics. X-ray magnetic circular dichroism (X-MCD) is used as element-specific magnetic contrast mechanism similar to photoemission electon microscopy (PEEM), however, with volume sensitivity and the ability to record the images in varying applied magnetic fields which allows to study magnetization reversal processes at fundamental length scales. Utilizing a stroboscopic pump-probe scheme one can investigate fast spin dynamics with a time resolution down to 70 ps which gives access to precessional and relaxation phenomena as well as spin torque driven domain wall dynamics in nanoscale systems. Current developments in zone plate optics aim for a spatial resolution towards 10nm and at next generation X-ray sources a time resolution in the fsec regime can be envisioned.Keywords magnetic soft X-ray microscopy, X-ray optics, Fresnel zone plates, magnetic nanostructures, magnetization reversal, fast spin dynamics, X-ray magnetic circular dichroism 3

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“…Ultrafast magnetization excitations in soft magnetic microstructures thus recently attracted particular attention. [5][6][7][8][9][10] New switching concepts involving the spin transfer torque 11,12 also rely on gyromagnetic processes. For microscopic elements with a small magnetic anisotropy and a welldefined shape, the high-frequency behavior is governed by confined spin wave eigenmodes.…”

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Magnetization dynamics in microscopic spin-valve elements: Shortcomings of the macrospin picture

et al. 2007

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We have studied ultrafast magnetodynamics in micropatterned spin-valve structures using time-resolved x-ray photoemission electron microscopy combined with x-ray magnetic circular dichroism. Exciting the system with ultrafast field pulses of 250 ps width, we find the dynamic response of the free layer to fall into two distinctly different contributions. On the one hand, it exhibits localized spin wave modes that strongly depend on the shape of the micropattern. A field pulse applied perpendicular to the exchange bias field along the diagonal of a square pattern leads to the excitation of a standing spin wave mode with two nodes along the field direction. This mode is strongly suppressed for a pattern of elliptical shape. On the other hand, the integrated response of the free layer roughly follows a single-spin model with a damping constant of ␣ = 0.025 independent of the shape and resembles the response of a critically damped forced oscillator. DOI: 10.1103/PhysRevB.76.134410 PACS number͑s͒: 75.40.Gb, 75.60.Ϫd, 75.75.ϩa A magnetic spin valve ͑SV͒ represents a very important functional structure in modern magnetism. SVs are extensively used as read heads in magnetic storage devices. Their functionality depends crucially on the interplay of magnetic coupling phenomena. In its simplest version, a SV is composed of two ferromagnetic ͑FM͒ layers separated by a nonmagnetic ͑NM͒ spacer layer mediating a usually antiferromagnetic indirect exchange coupling, 1,2 which determines the magnetic configuration of the layer stack. In a more refined approach, the magnetization in one of the FM layers ͑hard layer͒ is additionally stabilized by a strong coupling ͑exchange biasing͒ to an antiferromagnet. The orientation of the magnetization vector in the other-the free-FM layer is then sensed by the giant magnetoresistance ͑GMR͒ effect. 2,3 In more complex systems, further coupling mechanisms such as orange peel or edge coupling may take place. 4 Thus, micron-sized spin valves are extremely interesting structures from a fundamental point of view, as they provide a unique access to the interplay between different types of magnetic coupling in both static and dynamic experiments.Advanced magnetic recording schemes and spintronics push the switching time into the gyromagnetic regime. Ultrafast magnetization excitations in soft magnetic microstructures thus recently attracted particular attention. 5-10 New switching concepts involving the spin transfer torque 11,12 also rely on gyromagnetic processes. For microscopic elements with a small magnetic anisotropy and a welldefined shape, the high-frequency behavior is governed by confined spin wave eigenmodes. 5,6,13 Quantitatively, the magnetodynamic response may be described by thewith the magnetization M ជ , the gyromagnetic ratio ␥, the Gilbert damping parameter ␣, and the saturation magnetization M s . 14 The effective field H ជ ef f contains all coupling contributions and exerts a torque on M ជ , which initiates its precessional motion, if the Fourier spectrum of the exciting ext...

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Vortex Core-Driven Magnetization Dynamics

Cited by 600 publications

References 11 publications

Symmetry breaking in the formation of magnetic vortex states in a permalloy nanodisk

Symmetry breaking in the formation of magnetic vortex states in a permalloy nanodisk

Exploring nanomagnetism with soft X-ray microscopy

Magnetization dynamics in microscopic spin-valve elements: Shortcomings of the macrospin picture

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