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

Coffey, W. T.; Déjardin, Pierre-Michel; Kalmykov, Yuri P.

doi:10.1103/physrevb.79.054401

Cited by 13 publications

(12 citation statements)

References 47 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%

“…and _ uðtÞ ¼ cuðtÞ Â ½HðtÞþhðtÞ À cauðtÞ Â ½uðtÞ Â HðtÞ; (95) u ¼ M=M S . The difference between these two models is that in the Kubo equation (95) the random field hðtÞ appears only in the gyromagnetic term.…”

Section: Reversal Time Of the Magnetization In Superparamagnets Wmentioning

confidence: 99%

“…The magnetization relaxation rate problem for particles with mixed anisotropy (Eq. (160)) was implicitly identified by Smith and de Rozario, 82 Brown, 9 and Dormann et al, 48 while Newell 150 explicitly evaluated the IHD escape rate from the IHD equation (84), noting the absurd prediction of a vanishing escape rate for jfj ¼ 1: Now, insofar as the rate calculation in the vicinity of nonparabolic stationary points is concerned, a method for point Brownian particles or rigid rotators with separable and additive Hamiltonians has been suggested by Talkner and Ryter 151 and H€ anggi et al 53 This has been applied to a Brownian single-axis rotator in a periodic potential with nonparabolic barriers 152 and also has been recently extended to a singledomain particle with mixed anisotropy, 95 yielding a corresponding turnover formula for the reversal time of the magnetization s: Following the exposition of Ref. 95, we shall, for the purposes of illustration, confine our treatment to anisotropy ratios jfj 1: The calculations can be extended to jfj > 1 without major difficulties.…”

Section: F Mixed Anisotropy: Breakdown Of the Paraboloid Approximationmentioning

confidence: 99%

“…The results of the numerical 95 and asymptotic (from Eqs. (161) (turnover), (176), (177), (183), all pertaining to IHD) calculations of the normalized reversal time s=s 0 as functions of the anisotropy ratio parameter f and a are shown in Figs.…”

Section: F Mixed Anisotropy: Breakdown Of the Paraboloid Approximationmentioning

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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249

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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: Reversal Time Of the Magnetization In Superparamagnets Wmentioning

confidence: 99%

Section: F Mixed Anisotropy: Breakdown Of the Paraboloid Approximationmentioning

confidence: 99%

Section: F Mixed Anisotropy: Breakdown Of the Paraboloid Approximationmentioning

confidence: 99%

See 2 more Smart Citations

Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Coffey

Kalmykov

2012

Journal of Applied Physics

Self Cite

226

249

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“…The boundary conditions are defined by Eq. (25). Substituting h λ and rearranging keeping only the linear-ψ terms, one arrives at…”

Section: Screening and Other Generalizationsmentioning

confidence: 99%

Effective anisotropy due to the surface of magnetic nanoparticles

Garanin

2018

Phys. Rev. B

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Analytical solution has been found for the second-order effective anisotropy of magnetic nanoparticles of a cubic shape due to the surface anisotropy (SA) of the Néel type. Similarly to the spherical particles, for the simple cubic lattice the grand-diagonal directions (±1, ±1, ±1) are favored by the effective cubic anisotropy but the effect is twice as strong. Uniaxial core anisotropy and applied magnetic field cause screening of perturbations from the surface at the distance of the domain-wall width and reduce the effect of SA near the energy minima. However, screening disappears near the uniaxial energy barrier, and the uniform barrier state of larger particles may become unstable. For these effects the analytical solution is obtained as well, and the limits of the additive formula with the uniaxial and effective cubic anisotropies for the particle are established. Thermally-activated magnetization-switching rates have been computed by the pulse-noise technique for the stochastic Landau-Lifshitz equation for a system of spins.PACS numbers: 02.50. Ey, As it was mentioned in Ref. [16], in the presence of the uniaxial core anisotropy D, the effect of the surface will be screened at the distance of the domain-wall width δ = a J/(2D) from the surfaces, a being the lattice arXiv:1803.10406v1 [cond-mat.mes-hall]

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