Giant nonlocal damping by spin-wave emission: Micromagnetic simulations

Eilers, Gerrit; Lüttich, M.; Münzenberg, Markus

doi:10.1103/physrevb.74.054411

Cited by 14 publications

(12 citation statements)

References 27 publications

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“…A symmetric pattern would indicate that the excitation results from the transient out-of-plane demagnetizing field [14]. In contrast, the torque induced by a symmetric transient in-plane demagnetizing field [34] is actually antisymmetric, which would result in an antisymmetric spin wave emission pattern. The presence of both mechanisms produces the mixed pattern shown in Fig.…”

Section: Prl 110 097201 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Direct Excitation of Propagating Spin Waves by Focused Ultrashort Optical Pulses

Dvornik

Davison

et al. 2013

Phys. Rev. Lett.

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An all-optical experiment long utilized to image phonons excited by ultrashort optical pulses has been applied to a magnetic sample. In addition to circular ripples due to surface acoustic waves, we observe an X-shaped pattern formed by propagating spin waves. The emission of spin waves from the optical pulse epicenter in the form of collimated beams is qualitatively reproduced by micromagnetic simulations. We explain the observed pattern in terms of the group velocity distribution of Damon-Eshbach magnetostatic spin waves in the reciprocal space and the wave vector spectrum of the focused ultrafast laser pulse. DOI: 10.1103/PhysRevLett.110.097201 PACS numbers: 75.30.Ds, 75.50.Bb, 75.78.Cd, 75.78.Jp The recent proliferation of studies on the interaction of femtosecond optical pulses with magnetic materials [1] has been primarily concerned with exploration and understanding of novel types of ultrafast magnetic phase transitions and the associated promise of a new paradigm of high speed magnetic data storage technology [2][3][4][5][6][7][8][9][10][11][12][13]. Far less attention has been paid to the possibility of using the ultrafast optical excitation to induce magnetization precession and propagating spin waves [14][15][16][17][18]. However, such practice could lead to important applications (at least in the context of fundamental research) in the emerging field of ''magnonics'' [19,20]. An important breakthrough was recently achieved by Satoh et al., who demonstrated alloptical imaging of propagating magnetostatic spin waves of about 100 m wavelength excited by ultrafast optical pulses in a ferromagnetic dielectric [18]. However, despite the importance of magnetic dielectrics and long wavelength magnetostatic spin waves [21], the ultimate goal of magnonics requires that much shorter wavelength spin waves be excited and studied in magnetic thin films and nanostructures [16,19].In this Letter, we demonstrate that femtosecond optical pulses focused to a diffraction limited spot by a high quality microscope objective are able to excite spin waves at specific locations on the surface of a thin magnetic film. The propagation of the optically excited spin waves is imaged using a setup labeled here as time resolved optically pumped scanning optical microscope (TROPSOM), which has applications beyond the fields of magnonics and optomagnetism. The employed experimental scheme has been utilized to image optically excited propagating phonons [22], which are also observed in our experiments. As compared to the more conventional methods of spin wave excitation by current carrying microstrips [19,21], TROPSOM yields the benefit of broadband point magnonic sources, which could otherwise be only obtained by means of complex nanofabrication [23]. Inspired by the recent demonstrations of spin wave emission by resonant transducers under a uniform microwave field [24,25], one could even imagine building similar devices to enable effective conversion of the femtosecond laser light into a tailored spin wave emission pattern on a ...

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Section: Prl 110 097201 (2013) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Direct Excitation of Propagating Spin Waves by Focused Ultrashort Optical Pulses

Dvornik

Davison

et al. 2013

Phys. Rev. Lett.

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“…For example, the spatial profile of a pulsed magnetic field or a focused pump laser spot may lead to the generation of magnons that propagate away from the region that is being probed. Eilers et al 24 performed simulations of nonlocal damping by spin-wave emission and found that spin-wave emission becomes a significant damping mechanism when the excitation area is less than 1 m, while Wu et al 25 showed that propagation of magnetostatic spin waves could be significant even for probed regions of tens of microns in size.…”

Section: Introductionmentioning

confidence: 99%

Optically induced magnetization dynamics and variation of damping parameter in epitaxialCo2MnSiHeusler alloy films

et al. 2010

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All-optical pump-probe measurements of magnetization dynamics have been performed upon epitaxial Co 2 MnSi͑001͒ Heusler alloy thin films annealed at temperatures of 300, 400, and 450°C. An ultrafast laserinduced modification of the magnetocrystalline anisotropy triggers precession which is detected by timeresolved magneto-optical Kerr effect measurements. From the damped oscillatory Kerr rotation, the frequency and relaxation rate of the precession is determined. Using a macrospin solution of the Landau-Lifshitz-Gilbert equation the effective fields acting upon the sample magnetization are deduced. This reveals that the magnetization is virtually independent of the annealing temperature while the fourfold magnetocrystalline anisotropy decreases dramatically with increasing annealing temperature as the film structure changes between the B2 and L2 1 phases. From the measured relaxation rates, the value of the apparent Gilbert damping parameter is found to depend strongly upon the static field strength and in-plane static field orientation. The variation of the apparent damping parameter is generally well reproduced by an inhomogeneous broadening model in which the presence of B2 and L2 1 phases leads to a large dispersion of the magnetocrystalline anisotropy. However, for the sample annealed at a temperature of 300°C, the lack of a detailed fit to the data suggests that the apparent anisotropy of the apparent damping parameter might alternatively arise due to a network of dislocations with fourfold symmetry.

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“…Gilbert damping is a spin relaxation phenomenon in magnetic systems which controls the rate at which the spins reach equilibrium. Spin-orbit coupling [32], non-local spin relaxations like spin wave dissipation [33,34] and disorder present in the materials are the major factors causing Gilbert damping. The damping parameter α values are 0.0096, 0.0083 and 0.0108 for x = 42, 83 and 249 nm respectively.…”

Section: Effect Of Czf Layer Thicknessmentioning

confidence: 99%