Two-magnon scattering and viscous Gilbert damping in ultrathin ferromagnets

Lenz, K.; Wende, Heiko; Kuch, W.; Baberschke, K.; Nagy, Kálmán; Jànossy, A.

doi:10.1103/physrevb.73.144424

Cited by 210 publications

(169 citation statements)

References 20 publications

(23 reference statements)

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“…A non-linear behaviour is also observed for sample S1 ( scattering [12,14,20]. Since we kept the thickness constant for the Co layer and other NM layers, we may assume that d-d electrons hybridization and two-magnon scattering will be similar contribution in all layers.…”

Section: …(4)mentioning

confidence: 75%

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Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Singh

Jena

2017

J. Phys. D: Appl. Phys.

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Abstract:We investigated the dependence of the seed (Ta/Pt, Ta/Au) and capping (Pt/Ta, Au/Ta) layers on spin pumping effect in the ferromagnetic 3 nm thick Co thin film using ferromagnetic resonance spectroscopy. The data is fitted with Kittel's equation to evaluate damping constant and g-factor. A strong dependence of seed and capping layers on spin pumping has been discussed. The value of damping constant (α) is found to be relatively large i.e. 0.0326±0.0008 for the Ta(3)/Pt(3)/Co(3)/Pt(3)/Ta(3) (nm) multilayer structure, while it is 0.0104±0.0003 for Ta(3)/Co(3)/Ta(3) (nm). Increase in α is observed due to Pt layer that works as a good sink for spins due to high spin orbit coupling. In addition, we measured the effective spin conductance  g = 2.00 ± 0.08 × 10 18 m -2 for the tri-layer structure Pt(3)/Co(3)/Pt(3) (nm) as a result of the enhancement in α relative to its bulk value.We observed that the evaluated g-factor decreases as effective demagnetizing magnetic field increases in all the studied samples. The azimuthal dependence of magnetic resonance field and line width showed relatively high anisotropy in the tri-layer Ta(3)/Co(3)/Ta(3) (nm) structure.

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Section: …(4)mentioning

confidence: 75%

“…However, other damping mechanisms e.g. inhomogeneities in the sample, two magnon scattering and interfaces might also play important role to enhance the damping effect [12][13][14][15][16]. The interfaces are very important for creating pure spin current and its dissipation.…”

Section: Introductionmentioning

confidence: 99%

Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Singh

Jena

2017

J. Phys. D: Appl. Phys.

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“…At lower temperature a superposition of twofold and fourfold symmetry dominates the angular dependence of the in-plane linewidth. This can be related to the shape and orientation of the defects (rectangular) that cause the two-magnon scattering [21,32,33]. The two-magnon scattering intensity depends on the direction of the magnetisation in respect to the symmetry axes of the magnetic defects and on the angle between the magnetisation and the crystallographic axes.…”

Section: Magnetic Relaxationmentioning

confidence: 99%

Ferromagnetic resonance and magnetic damping in C-doped Mn₅Ge₃

Dutoit¹,

Dolocan²,

Kuz’min³

et al. 2015

J. Phys. D: Appl. Phys.

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Abstract. Ferromagnetic resonance (FMR) was used to investigate the static and dynamic magnetic properties of carbon-doped Mn 5 Ge 3 (C 0.1 and C 0.2 ) thin films grown on Ge(111). The temperature dependence of magnetic anisotropy shows an increased perpendicular magneto-crystalline contribution at 80K with an in-plane easy axis due to the large shape contribution. We find that our samples show a small FMR linewidth (corresponding to an intrinsic magnetic damping parameter α=0.005), which is a measure of the spin relaxation and directly related with the magnetic and structural quality of the material. In the perpendicular-to-plane geometry, the FMR linewidth shows a minimum at around 200K for all the samples, which seems to be not correlated to the C-doping.Ferromagnetic resonance and magnetic damping in C-doped Mn 5 Ge 3 2The magnetic relaxation parameters have been determined and indicate the twomagnon scattering as the main extrinsic contribution. We observe a change in the main contribution from scattering centres in Mn 5 Ge 3 C 0.2 at low temperatures, which could be related to the minimum in linewidth.

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“…It is found that above some threshold magnetic field the uniform precessional mode, i.e., the k = 0 magnons decay into nonuniform magnons (k = 0), i.e., the Zeeman energy stays in the magnetic subsystem and scatters between magnon modes. [17][18][19][20] However, in ultrafast magnetization reversal the high-energy electrons generated by the laser field decay into the lower-energy magnon excitations. [22][23][24] In both cases spin-orbit coupling (SOC) is responsible for the transfer of the angular momentum to the lattice through different scattering mechanisms such as magnon-magnon, magnon-phonon, magnon-impurity scattering, and so on, where each process has a different relaxation time.…”

Section: -4mentioning

confidence: 99%

“…12 In current devices the switching speeds have reached a point where dynamical effects are becoming very important [12][13][14][15][16] Magnons are created in fast (field driven) as well as ultrafast (laser induced) magnetization reversal processes. [17][18][19][20][21][22][23][24][25][26] The former case is of particular interest for current device applications. It is found that above some threshold magnetic field the uniform precessional mode, i.e., the k = 0 magnons decay into nonuniform magnons (k = 0), i.e., the Zeeman energy stays in the magnetic subsystem and scatters between magnon modes.…”

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confidence: 99%

Strong magnon softening in tetragonal FeCo compounds

2013

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Magnons play an important role in fast precessional magnetization reversal processes serving as a heat bath for dissipation of the Zeeman energy and thus being responsible for the relaxation of magnetization. Employing ab initio many-body perturbation theory we studied the magnon spectra of the tetragonal FeCo compounds considering three different experimental c/a ratios, c/a = 1.13, 1.18, and 1.24 corresponding to FeCo grown on Pd, Ir, and Rh, respectively. We find that for all three cases the short-wavelength magnons are strongly damped and tetragonal distortion gives rise to a significant magnon softening. The magnon stiffness constant D decreases almost by a factor of 2 from FeCo/Pd to FeCo/Rh. The combination of soft magnons together with the giant magnetic anisotropy energy suggests FeCo/Rh to be a promising material for perpendicular magnetic recording applications. Since the introduction of the first commercial hard disk drive in 1956, the recording density in a hard disk, that is, the amount of information that can be stored per square inch, has increased by more than seven orders of magnitude to meet an ever-growing need.1 This has been achieved by a simple scaling of the dimensions of the bits recorded in storage medium. Due to the superparamagnetic effect, however, the recording density has an upper limit. For longitudinal magnetic recording it is around 200 Gbit per square inch, whereas it is predicted to be much larger for perpendicular recording, up to 1000 Gbit per square inch, though this limit is constantly changing with the discovery of new materials. 2-4The major problem in designing magnetic storage media is to retain the magnetization of the medium over a long period of time despite thermal fluctuations. If the ratio of the thermal energy k B T to the magnetic energy per grain K u V , where V is the grain volume and K u is the uniaxial magnetocrystalline anisotropy energy (MAE), becomes sufficiently large, the thermal fluctuations can reverse the magnetization in a region of the medium, destroying the data stored there. 3,5 In order to further increase the recording density in future recording media, high-K u materials are needed. 6 Additionally, a large saturation magnetization M s is beneficial to reduce the write field, which has to be applied by the writing head. Materials that combine the desired large values of K u and M s are tetragonal near-equiatomic FeCo alloys. The large values of K u and M s in these alloys were first predicted by first-principles calculations 7 and then confirmed by experiments. [8][9][10][11] In particular, Yildiz et al.11 achieved a strong perpendicular magnetic anisotropy (PMA) in tetragonal FeCo alloys epitaxially grown on Pd (c/a = 1.13), Ir (c/a = 1.18), and Rh (c/a = 1.24) substrates. The authors found that the PMA is very sensitive to the tetragonal distortion and increases with increasing c/a ratio, which allows to tune the PMA by growing the alloys on different substrates.Besides large K u and M s values, another very important issue in magnetic recor...

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Two-magnon scattering and viscous Gilbert damping in ultrathin ferromagnets

Cited by 210 publications

References 20 publications

Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Ferromagnetic resonance and magnetic damping in C-doped Mn₅Ge₃

Strong magnon softening in tetragonal FeCo compounds

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Two-magnon scattering and viscous Gilbert damping in ultrathin ferromagnets

Cited by 210 publications

References 20 publications

Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Study of spin pumping in Co thin film vis-à-vis seed and capping layers using ferromagnetic resonance spectroscopy

Ferromagnetic resonance and magnetic damping in C-doped Mn5Ge3

Strong magnon softening in tetragonal FeCo compounds

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Ferromagnetic resonance and magnetic damping in C-doped Mn₅Ge₃