High-resolution imaging of fast magnetization dynamics in magnetic nanostructures

Stoll, Hermann; Puzic, A.; Waeyenberge, Bartel Van; Fischer, Peter; Raabe, Jörg; Buess, Matthias; Haug, Tobias; Höllinger, Rainer; Back, Christian; Weiss, Dieter; Denbeaux, Gregory

doi:10.1063/1.1723698

Cited by 150 publications

(116 citation statements)

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“…Fig. 5 (a) shows the scheme of the zone plate optics and the results obtained around the L 3,2 absorption edge of a Gd 25 Fe 75 amorphous film are displayed in Fig 5 (b,c). The boundary of the magnetic domain patterns are enhanced at a photon energy of 705eV and 711eV, where no 11 absorption contrast is expected.…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

“…[21][22][23][24][25]. As a pure photon-in/photon-out based technique the images can be recorded in external magnetic fields giving access to study magnetization reversal phenomena on the nanoscale.…”

Section: Introductionmentioning

confidence: 99%

Exploring nanomagnetism with soft X-ray microscopy

et al. 2007

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“…10͔͒, using either fluorescence, [2][3][4]8,10,11,13,16 reflectivity, 2,8 or transmission measurements. 1,5,6,8,9,12,14,15,17 Ferromagnetic resonance signals have been observed at energies from 500 eV to 7 keV on the following atoms: Fe ͑L 3 / L 2 -edges and K-edge͒, Ni ͑L 3 / L 2 -edges͒, Co ͑L 3 / L 2 -edges͒, Gd ͑M 4 / M 5 -edges͒, Y ͑L 3 / L 2 -edges͒, O ͑K-edge͒, and Tb ͑M 5 -edge͒. These experiments allowed element-specific studies of the magnetization precession in ferromagnetic 2,8,9 and ferrimagnetic 3,10,11,13,16 compounds as well as measurements of the relative phase and precession angle of the magnetization in coupled metal layers.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Element sensitivity is obtained by choosing the x-ray photon energy corresponding to a core-to-valence band transition of the atom under investigation. The relatively large separation between the absorption lines of the different elements at the x-ray energies of interest as well as the x-ray absorption line shape dependence on the type and position of neighbor atoms allows one to study the magnetic properties of each element separately in well defined environments.…”

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confidence: 99%

Longitudinal detection of ferromagnetic resonance using x-ray transmission measurements

Boero

Rusponi

Kavich

et al. 2009

Review of Scientific Instruments

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We describe a setup for the x-ray detection of ferromagnetic resonance in the longitudinal geometry using element-specific transmission measurements. Thin magnetic film samples are placed in a static magnetic field collinear with the propagation direction of a polarized soft x-ray beam and driven to ferromagnetic resonance by a continuous wave microwave magnetic field perpendicular to it. The transmitted photon flux is measured both as a function of the x-ray photon energy and as a function of the applied static magnetic field. We report experiments performed on a 15 nm film of doped Permalloy ͑Ni 73 Fe 18 Gd 7 Co 2 ͒ at the L 3 / L 2 -edges of Fe, Co, and Ni. The achieved ferromagnetic resonance sensitivity is about 0.1 monolayers/ ͱ Hz. The obtained results are interpreted in the framework of a conductivity tensor based formalism. The factors limiting the sensitivity as well as different approaches for the x-ray detection of ferromagnetic resonance are discussed.

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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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High-resolution imaging of fast magnetization dynamics in magnetic nanostructures

Cited by 150 publications

References 18 publications

Exploring nanomagnetism with soft X-ray microscopy

Exploring nanomagnetism with soft X-ray microscopy

Longitudinal detection of ferromagnetic resonance using x-ray transmission measurements

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

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