Dynamics of an ensemble of single-domain magnetic particles

Garanin, D. A.; Ishchenko, V. V.; Панина, Л. В.

doi:10.1007/bf01079045

Cited by 95 publications

(109 citation statements)

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“…Some theoretical estimations of ␣ yield values of order of 0.01-0.1. 22 The comparison of the effective eigenvalue solutions 15,19,21 with the exact results allows us to estimate the accuracy of the former. In Figs.…”

Section: ͑413͒mentioning

confidence: 99%

“…To a certain extent this effect is analogous to inhomogeneous broadening and considerably exceeds the true damping. 15 Therefore, it is practically impossible to describe asymmetric absorption and dis- persion curves by the usual single resonance spectrum which is predicted by the effective eigenvalue approach. However, in the high barrier limit ( ӷ1) when the anisotropy potential may be approximated by a harmonic potential the system may be effectively described by a single resonance with the characteristic frequency 0 given by Eq.…”

Section: ͑413͒mentioning

confidence: 99%

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Transverse complex magnetic susceptibility of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a longitudinal uniform magnetic field

Kalmykov

Coffey

1997

Phys. Rev. B

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The infinite hierarchy of differential-recurrence relations for the equilibrium transverse correlation functions appropriate to magnetic relaxation of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a uniform external magnetic field H 0 is derived by averaging Gilbert's equation. Exact expressions in terms of matrix continued fractions for the transverse complex magnetic susceptibility are obtained with the aid of linear-response theory by solving the infinite hierarchy. The principal features of the spectra are emphasized in figures showing the real and imaginary parts of the complex magnetic susceptibility. The accuracy and the range of the applicability of analytical results based on the effective eigenvalue method is established. It is shown that this method provides in general a good approximation to the exact solution with the exception of the range of low-to-intermediate barrier heights of the anisotropy potential where at small H 0 there exists essentially a spread of the precession frequencies of the magnetization.

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Section: ͑413͒mentioning

confidence: 99%

Section: ͑413͒mentioning

confidence: 99%

Transverse complex magnetic susceptibility of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a longitudinal uniform magnetic field

Kalmykov

Coffey

1997

Phys. Rev. B

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“…Recently two ways were proposed to obtain quadrature formulas for τ int . One method [19] implies a direct integration of the Fokker-Planck equation. Another method [20] involves solving three-term recurrence relations for the statistical moments of W .…”

Section: Asymptotic Integral Timementioning

confidence: 99%

Linear and nonlinear superparamagnetic relaxation at high anisotropy barriers

Raǐkher

Stepanov

2002

Phys. Rev. B

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The micromagnetic Fokker-Planck equation is solved for a uniaxial particle in the low-temperature limit. Asymptotic series in the parameter that is the inverse barrier height-to-temperature ratio are derived. With the aid of these series, the expressions for the superparamagnetic relaxation time and the odd-order dynamic susceptibilities are presented. The obtained formulas are both quite compact and practically exact in the low (with respect to FMR) frequency range that is proved by comparison with the numerically-exact solution of the micromagnetic equation. The susceptibilities formulas contain angular dependencies that allow to consider textured as well as randomly oriented particle assemblies. Our results advance the previous two-level model for nonlinear superparamagnetic relaxation.

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“…There are rather fluctuations of the crystal-field anisotropy tensor. This leads to a more complicated model of noise [3] that was not explored, however. The model above, although physically questionable, is the simplest possible model and it does not lead to visible inconsistencies.…”

Section: Introductionmentioning

confidence: 99%

“…Microscopic theories always suggest λ 1. It was shown that the vector product in the noise term dictates the double-vector product form of the LandauLifshitz damping term [3]. For instance, in the case of noise being anisotropic, the damping term has to be accordingly modified.…”

Section: Introductionmentioning

confidence: 99%

Pulse-noise approach for classical spin systems

Garanin

2017

Phys. Rev. E

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For systems of classical spins interacting with the bath via damping and thermal noise, the approach is suggested to replace the white noise by a pulse noise acting at regular time intervals ∆t, within which the system evolves conservatively. The method is working well in the typical case of a small dimensionless damping constant λ and allows a considerable speed-up of computations by using high-order numerical integrators with a large time step δt (up to a fraction of the precession period), while keeping δt ∆t to reduce the relative contribution of noise-related operations. In cases when precession can be discarded, δt can be increased up to a fraction of the relaxation time ∝ 1/λ that leads to a further speed-up. This makes equilibration speed comparable with that of Metropolis Monte Carlo. The pulse-noise approach is tested on single-spin and multi-spin models.

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Dynamics of an ensemble of single-domain magnetic particles

Cited by 95 publications

References 1 publication

Transverse complex magnetic susceptibility of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a longitudinal uniform magnetic field

Transverse complex magnetic susceptibility of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a longitudinal uniform magnetic field

Linear and nonlinear superparamagnetic relaxation at high anisotropy barriers

Pulse-noise approach for classical spin systems

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