Modal spectrum of permalloy disks excited by in-plane magnetic fields

Neudecker, Ingo; Perzlmaier, Korbinian; Hoffmann, Frank; Woltersdorf, Georg; Buess, Matthias; Weiss, Dieter; Back, Christian

doi:10.1103/physrevb.73.134426

Cited by 78 publications

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“…The experimentally determined induced uniaxial anisotropy as a function of the reciprocal stripe width is shown in H rf I rf [1][2][3][4][5][6][7][8][9][10] [110] . As expected for large stripe widths, the induced anisotropy approaches zero because the strain-relaxation effects become negligible.…”

Section: 13mentioning

confidence: 99%

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Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

et al. 2009

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Anisotropic strain relaxation in ͑Ga,Mn͒As nanostructures was studied combining time-resolved Kerr microscopy and ferromagnetic resonance techniques. Local resonance measurements on individual narrow stripes patterned along various crystallographic directions reveal that the easy axis of the magnetization can be forced perpendicular to the strain relaxation direction. Spatially resolved measurements on disk-shaped and rectangular ͑Ga,Mn͒As structures allow us to directly visualize these local changes in the magnetic anisotropy. We show that the strain-induced edge anisotropy allows for an effective control of the coercive field in stripe structures. DOI: 10.1103/PhysRevB.80.054417 PACS number͑s͒: 75.75.ϩa, 75.30.Gw, 75.50.Pp, 76.50.ϩg The magnetic properties of the diluted magnetic semiconductor ͑Ga,Mn͒As have been studied intensely using ferromagnetic resonance ͑FMR͒, superconducting quantum interference device ͑SQUID͒ magnetometry, magnetotransport, and Hall-effect measurements due to the potential application of this material in spintronics devices. In order to understand and engineer the magnetotransport properties of such structures it is of utmost importance to understand and control the magnetic anisotropies and the switching behavior. The magnetic anisotropies in ͑Ga,Mn͒As depend on a multitude of parameters such as temperature, 1 hole concentration, 2 and postgrowth annealing. 3 Recent experiments have shown that the magnetic anisotropies can be manipulated by either applying mechanical stress to the sample 4 or by releasing the strain-induced anisotropy with lithographic methods. [5][6][7] It has also been demonstrated that the easy axis of the magnetization can be rotated by varying the hole concentration using a strong electric field.8 However, all these experiments do not resolve magnetic anisotropies in ͑Ga,Mn͒As microand nanostructures locally; the signal in magnetoresistance measurements is always proportional to the average magnetization of the structure.The experiments presented here allow us to perform spatially resolved measurements of the magnetic anisotropy with a resolution of 500 nm. We have investigated ͑Ga,Mn͒As films grown on GaAs͑001͒ which due to the lattice mismatch grow compressively strained. This strain gives rise to a strong perpendicular magnetic anisotropy with easy axes in the film plane. By patterning a ͑Ga,Mn͒As film into small structures this strain can be partially relieved, strongly affecting the magnetic anisotropies. Our approach combines the advantages of two experimental techniques: angledependent FMR provides direct access to the energy landscape and the magnetic anisotropies and time-resolved scanning Kerr microscopy allows us to perform time and spatially resolved measurements. Thus these experiments can serve to visualize the local variations in the magnetic anisotropy.The Ga 1−x Mn x As films were grown on GaAs͑001͒ substrates by molecular-beam epitaxy. On the GaAs͑001͒ substrate a 50-nm-thick high-temperature AlGaAs-buffer layer and a 8-nm-thick low-tempera...

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Section: 13mentioning

confidence: 99%

“…Spatial resolution is obtained by scanning the sample using a piezotable and is limited to about 500 nm. 9,10 The high resolution was obtained by using an objective lens with a numerical aperture of 0.6 and a wavelength of 400 nm. The sample is mounted in an optical cryostat.…”

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Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

et al. 2009

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“…Now let us discuss the magnetization switching process induced by vortex dynamics. Several excitations such as gyrotropic motion of vortex core, azimuthal spin waves, and radial spin waves have been observed in H rf -induced vortex dynamics for a single soft magnetic disk [7,[18][19][20]. In order to assign which dynamical mode is responsible for the switching we observed,…”

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Vortex-dynamics-mediated low-field magnetization switching in an exchange-coupled system

et al. 2016

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“…The lowest frequency excitation corresponds to the gyrotropic mode when the vortex moves as a whole around an equilibrium position [7][8][9], meanwhile the higher frequency modes correspond to the spin waves excited mainly outside of the vortex core [10][11][12][13][14][15][16][17][18][19]. The spin wave having radial or azimuthal symmetry with respect to the dot center are described by integers (n, m), which indicate number of nodes in the dynamic magnetization along radial (n) and azimuthal (m) directions.…”

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Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

et al. 2009

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We report on linear spin dynamics in the vortex state of the Permalloy dots subjected to stratified (magnetic) field. We demonstrate experimentally and by simulations the existence of two distinct dynamic regimes corresponding to the vortex stable and metastable states.Breaking cylindrical symmetry leads to unexpected eigenmodes frequency splitting in the stable state and appearance of new eigenmodes in the metastable state above the vortex nucleation field. Dynamic response in the metastable state strongly depends on relative orientation of the external rf pumping and the bias magnetic fields. These findings may be relevant for different vortex states in confined and stratified conditions.

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Modal spectrum of permalloy disks excited by in-plane magnetic fields

Cited by 78 publications

References 52 publications

Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

Mapping the magnetic anisotropy in (Ga,Mn)As nanostructures

Vortex-dynamics-mediated low-field magnetization switching in an exchange-coupled system

Spin waves in circular soft magnetic dots at the crossover between vortex and single domain state

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