Damping dependence of the magnetization relaxation time of single-domain ferromagnetic particles

Kalmykov, Yuri P.; Coffey, W. T.; Ouari, Bachir; Titov, S. V.

doi:10.1016/j.jmmm.2004.11.233

Cited by 34 publications

(23 citation statements)

References 32 publications

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“…(92) below). The turnover escape rate formula for superparamagnets has been exhaustively verified by numerical calculations in many publications, [89][90][91][92][93][94][95][96][97] where it has been compared with that calculated numerically from either the appropriate Fokker-Planck or Langevin equations and via computer simulations in all damping ranges including VLD, IHD, and VHD limits (see Secs. III and IV below).…”

Section: Superparamagnetic Relaxation Time: Brown's Approachmentioning

confidence: 97%

“…Thus both regimes of damping (IHD and VLD) can occur reflecting the fact that the dynamics of the transverse response affect the dynamics of the longitudinal response and vice versa. However, this fact appears not to have been explicably recognized in the first calculations of the magnetization reversal time of superparamagnets with nonaxially symmetric anisotropy by Smith 83,84 realized that the various Kramers damping regimes also applied to magnetic relaxation of single domain ferromagnetic particles and derived the corresponding VLD formula (90) which is effectively the same as the corresponding Kramers result for point particles (Eq. (12)).…”

Section: Superparamagnetic Relaxation Time: Brown's Approachmentioning

confidence: 99%

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Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Coffey

Kalmykov

2012

Journal of Applied Physics

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The reversal time, superparamagnetic relaxation time, of the magnetization of fine single domain ferromagnetic nanoparticles owing to thermal fluctuations plays a fundamental role in information storage, paleomagnetism, biotechnology, etc. Here a comprehensive tutorial-style review of the achievements of fifty years of development and generalizations of the seminal work of Brown [Phys. Rev. 130, 1677] on thermal fluctuations of magnetic nanoparticles is presented. Analytical as well as numerical approaches to the estimation of the damping and temperature dependence of the reversal time based on Brown's Fokker-Planck equation for the evolution of the magnetic moment orientations on the surface of the unit sphere are critically discussed while the most promising directions for future research are emphasized. V C 2012 American Institute of Physics. [http://dx

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Section: Superparamagnetic Relaxation Time: Brown's Approachmentioning

confidence: 97%

Section: Superparamagnetic Relaxation Time: Brown's Approachmentioning

confidence: 99%

Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Coffey

Kalmykov

2012

Journal of Applied Physics

Self Cite

233

249

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“…6 Followed by Brown's initial work, 6 theoretical formulae of the attempt frequency for different potential symmetry were proposed. [10][11][12][13][14][15][16][17] Accurate theoretical formulae of the attempt frequency are necessary for modeling experiments and predicting quantitatively the superparamagnetic limit for device applications.…”

Section: Introductionmentioning

confidence: 99%

Attempt frequency of magnetization in nanomagnets with thin-film geometry

et al. 2008

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Solving the stochastic Landau-Lifshitz-Gilbert equation numerically, we investigate the effect of the potential landscape on the attempt frequency of magnetization in nanomagnets with the thin-film geometry. Numerical estimates of the attempt frequency are analyzed in comparison with theoretical predictions from the Fokker-Planck equation for the Néel-Brown model. It is found that for a nanomagnet with the thin-film geometry, theoretically predicted values for the universal case are in excellent agreement with numerical estimates.

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“…For ͉͉ ӷ 1, where the paraboloid approximations hold, the universal equation ͑6͒ has already been checked against numerical calculations of the magnetization relaxation time in Ref. 19.…”

Section: Reversal Time For Mixed Anisotropymentioning

confidence: 99%

Reversal time of the magnetization of single-domain ferromagnetic particles with mixed uniaxial and cubic anisotropy

2009

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The reversal time of the magnetization of single-domain ferromagnetic particles is estimated for mixed uniaxial and cubic anisotropy energies possessing nonparaboloidal saddles and well bottoms or either. The calculation generalizes the existing adaptation of the Kramers escape rate theory to fine ferromagnetic particles with nonaxially symmetric magnetocrystalline-Zeeman energies, originally based on the paraboloidal approximation for the energy near its stationary points, yielding in addition a simple universal Kramers turnover formula ͑based on the Mel'nikov-Meshkov depopulation factor͒ for the reversal time valid for all values of the damping. The asymptotic solution is compared with the appropriate numerically exact solution of the corresponding Fokker-Planck equation for the probability density function of magnetization orientations. The predictions of the generalized nonparaboloidal stationary point turnover formula agree with the numerical solution for a wide range of damping and other parameters characterizing the mixed anisotropy.

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Damping dependence of the magnetization relaxation time of single-domain ferromagnetic particles

Cited by 34 publications

References 32 publications

Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Attempt frequency of magnetization in nanomagnets with thin-film geometry

Reversal time of the magnetization of single-domain ferromagnetic particles with mixed uniaxial and cubic anisotropy

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