Theory of the magnetic damping constant

Suhl, H.

doi:10.1109/20.706720

Cited by 183 publications

(92 citation statements)

References 10 publications

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“…In particular, it can be evaluated from the resonant line width in ferromagnetic-resonance (FMR) experiments. The difficulty of these measurements consists in the problem that there exist several different sources for the broadening of the line width, which have been discussed extensively in the literature [7][8][9][10][11][12][13] . The line width that is observed in ferromagnetic resonance spectra is usually caused by intrinsic and extrinsic relaxation effects.…”

Section: Introductionmentioning

confidence: 99%

First-principles calculation of the Gilbert damping parameter via the linear response formalism with application to magnetic transition metals and alloys

et al. 2013

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A method for the calculations of the Gilbert damping parameter α is presented, which based on the linear response formalism, has been implemented within the fully relativistic Korringa-KohnRostoker band structure method in combination with the coherent potential approximation alloy theory. To account for thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. This allows the determination of α for various types of materials, such as elemental magnetic systems and ordered magnetic compounds at finite temperature, as well as for disordered magnetic alloys at T = 0 K and above. The effects of spin-orbit coupling, chemical and temperature induced structural disorder are analyzed. Calculations have been performed for the 3d transition-metals bcc Fe, hcp Co, and fcc Ni, their binary alloys bcc Fe1−xCox, fcc Ni1−xFex, fcc Ni1−xCox and bcc Fe1−xVx, and for 5d impurities in transition-metal alloys. All results are in satisfying agreement with experiment.

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Section: Introductionmentioning

confidence: 99%

First-principles calculation of the Gilbert damping parameter via the linear response formalism with application to magnetic transition metals and alloys

et al. 2013

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“…The resultant additional linewidth broadening would then be regarded as an extrinsic contribution to the damping [34][35][36] . While in isotropic films which exhibit low crystalline anisotropy or in films having in-plane crystalline anisotropy, twomagnon scattering is maximized when the external field is applied in the film plane, in PMA films this is not necessarily the case and the highest efficiency of two-magnon scattering may be obtained at some oblique angle 35 .…”

Section: Considerations Of Two-magnon Scatteringmentioning

confidence: 99%

Determination of intrinsic damping of perpendicularly magnetized ultrathin films from time-resolved precessional magnetization measurements

et al. 2015

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Abstract:Magnetization dynamics are strongly influenced by damping, namely the loss of spin angular momentum from the magnetic system to the lattice. An "effective" damping constant αeff is often determined experimentally from the spectral linewidth of the free induction decay of the magnetization after the system is excited to its non-equilibrium state. Such an αeff, however, reflects both intrinsic damping as well as inhomogeneous broadening that arises, for example, from spatial variations of the anisotropy field. In this paper we compare measurements of the magnetization dynamics in ultrathin non-epitaxial films having perpendicular magnetic anisotropy using two different techniques, timeresolved magneto optical Kerr effect (TRMOKE) and hybrid optical-electrical ferromagnetic resonance (OFMR). By using an external magnetic field that is applied at very small angles to the film plane in the TRMOKE studies, we develop an explicit closedform analytical expression for the TRMOKE spectral linewidth and show how this can be used to reliably extract the intrinsic Gilbert damping constant. The damping constant determined in this way is in excellent agreement with that determined from the OFMR method on the same samples. Our studies indicate that the asymptotic high-field approach that is often used in the TRMOKE method to distinguish the intrinsic damping from the 2 effective damping may result in significant error, because such high external magnetic fields are required to make this approach valid that they are out of reach. The error becomes larger the lower is the intrinsic damping constant, and thus may account for the anomalously high damping constants that are often reported in TRMOKE studies. In conventional ferromagnetic resonance (FMR) studies, inhomogeneous contributions can be readily distinguished from intrinsic damping contributions from the magnetic field dependence of the FMR linewidth. Using the analogous approach, we show how reliable values of the intrinsic damping can be extracted from TRMOKE in two distinct magnetic systems with significant perpendicular magnetic anisotropy: ultrathin CoFeB layers and Co/Ni/Co trilayers.3

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“…And, finally, the truly macroscopic length scale (of order of several microns or even millimeters), where the magnons created in the course of the reversal propagate. These magnons play an important role in energy transfer [1] and sometimes can initiate the magnetization reversal in other areas of the sample [2]. A similar picture of several interacting length scales appears in many situations, such as the breakthrough of a domain wall pinned by a defect [3], influence of the surface on the magnetic structure of the core of a magnetic particle [4] etc.…”

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confidence: 99%

“…The coarse-grained description is better than the micromagnetic even for the worst function f (2) µ,j . For the appropriately chosen weighting function f (1) µ,j , in spite of the cutoff, the difference with the exact solution is very small, even at maximal allowed wave vector values.…”

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confidence: 99%

Statistical coarse-graining as an approach to multiscale problems in magnetism

Dobrovitski

Katsnelson

Harmon

2000

Journal of Magnetism and Magnetic Materials

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Multiscale phenomena which include several processes occuring simultaneously at different length scales and exchanging energy with each other, are widespread in magnetism. These phenomena often govern the magnetization reversal dynamics, and their correct modeling is important. In the present paper, we propose an approach to multiscale modeling of magnets, applying the ideas of coarse graining. We have analyzed the choice of the weighting function used in coarse graining, and propose an optimal form for this function. Simple tests provide evidence that this approach may be useful for modeling of realistic magnetic systems. 75.40.Mg, 75.10.Hk, 05.70.Ln, 75.70.Cn A large number of phenomena taking place in magnets include processes occuring simultaneously at different length scales. A good example is the magnetization reversal in a macroscopic piece of magnetic material possessing different kinds of defects, voids, surfaces etc. The reversal starts by a nucleation of a domain with the magnetization opposite to the initial direction. As a rule, the nucleation happens near defects, where spins can be frustrated. Here, the different length scales involved can be clearly identified. First, there is the microscopic scale with a characteristic length of the order of several interatomic distances (several tens of angstroms), which corresponds to the region of spin frustration and contains the microstructure in the vicinity of the defect. Next, there is a "micromagnetic" length scale (of order of the domain wall width, several thousands of angstroms) where the formation of the general structure of the nucleus takes place. And, finally, the truly macroscopic length scale (of order of several microns or even millimeters), where the magnons created in the course of the reversal propagate. These magnons play an important role in energy transfer [1] and sometimes can initiate the magnetization reversal in other areas of the sample [2]. A similar picture of several interacting length scales appears in many situations, such as the breakthrough of a domain wall pinned by a defect [3], influence of the surface on the magnetic structure of the core of a magnetic particle [4] etc.Processes of this type, called multiscale processes, are receiving considerable attention nowadays. Along with very interesting and rich physics, these are the very processes which govern the switching behavior of magnetic systems (coercive field, switching time, etc.), so that an adequate understanding of multiscale phenomena is of paramount importance for development and creation of new magnetic storage media. Micromagnetic simulations can provide a realistic description of the processes taking place at both micromagnetic and macroscopic length scales. On the other hand, microscopic inhomogeneities require atomistic simulations (e.g., spin dynamics modeling [5] is an adequate tool for materials where spins are well localized at the sites of the crystalline lattice). However, for the description of real systems, all the length scales should be coupled, ...

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Theory of the magnetic damping constant

Cited by 183 publications

References 10 publications

First-principles calculation of the Gilbert damping parameter via the linear response formalism with application to magnetic transition metals and alloys

First-principles calculation of the Gilbert damping parameter via the linear response formalism with application to magnetic transition metals and alloys

Determination of intrinsic damping of perpendicularly magnetized ultrathin films from time-resolved precessional magnetization measurements

Statistical coarse-graining as an approach to multiscale problems in magnetism

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