Dependence of prefactor on the angle between an applied field and the easy axis for single-domain particles

Fukushima, Hiroshi; Uesaka, Y.; Nakatani, Yoshinobu; Hayashi, N.

doi:10.1016/j.jmmm.2010.08.021

Cited by 7 publications

(5 citation statements)

References 9 publications

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“…Apparently, τ VLD and λ −1 1 lie very close to each other for virtually all σ . Furthermore, in the high barrier limit, τ VLD as from the asymptotic equation (35) and its particular cases [Eqs. (A10), (B11), (A13), and (C10)] provide an accurate approximation to both λ −1 1 and τ VLD .…”

Section: Comparison Of Analytical and Numerical Resultsmentioning

confidence: 99%

“…(20) is that it is valid in parameter ranges where escape rate equations such as Eqs. (6), (10), (35), and (45) do not apply at all, i.e., both for low barriers and uniaxial crossovers [14,24]. Furthermore, for certain anisotropies such as uniaxial and biaxial anisotropies, etc., the VLD reversal time can be given in terms of integrals of known functions, e.g., Eqs.…”

Section: Discussionmentioning

confidence: 99%

“…(26)], the energy landscape is a uniform equatorial ridge (zone) separating two polar minima and has no saddle point. A detailed treatment of the oblique-field problem has been given by Coffey et al [31], Kennedy [32], Kalmykov et al [33,34], and Fukushima et al [35]. In particular, they showed that escape rate theory is in agreement with their numerical results, with computer simulations [36], and with experiments [5], emphasizing the vital importance of an accurate determination of the damping dependence of the reversal time.…”

Section: Vld Reversal Times For Uniaxial Anisotropymentioning

confidence: 92%

“…(9) and (43) can once more be considerably simplified, yielding Eq. (35), where f ± A and actions S ± ε C are given by Eqs. (A13) and (C10), respectively.…”

Section: Vld Reversal Times For Biaxial Anisotropymentioning

confidence: 99%

“…In the interval 0 ψ π/2 [note that τ (ψ) = τ (π − ψ)], τ VLD strongly depends on ψ, having a minimum at ψ ≈ π/4 and deviating considerably from the uniaxial asymptotic equation (6). However, in the limit of uniaxial crossover ψ → 0, τ VLD as from the asymptotic equation (35) diverges because the dimensionless action ± ε C → 0. Hence that equation cannot be used for the calculation of the reversal time.…”

Section: -7mentioning

confidence: 99%

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Magnetization reversal time of magnetic nanoparticles at very low damping

2014

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The magnetization reversal time of magnetic nanoparticles is investigated in the very low damping regime. The energy-controlled diffusion equation, rooted in a generalization of the Kramers escape rate theory for point Brownian particles in a potential to the magnetic relaxation of a macrospin, yields the reversal time in closed integral form. The latter is calculated for a nanomagnet with uniaxial anisotropy with a uniform field applied at an angle to the easy axis and for a nanomagnet with biaxial anisotropy with the field along the easy axis. The results completely agree with those yielded by independent numerical and asymptotic methods.

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Section: Comparison Of Analytical and Numerical Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Vld Reversal Times For Uniaxial Anisotropymentioning

confidence: 92%

“…(9) and (43) can once more be considerably simplified, yielding Eq. (35), where f ± A and actions S ± ε C are given by Eqs. (A13) and (C10), respectively.…”

Section: Vld Reversal Times For Biaxial Anisotropymentioning

confidence: 99%

Section: -7mentioning

confidence: 99%

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Magnetization reversal time of magnetic nanoparticles at very low damping

2014

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Nonlinear stationary ac response of the magnetization of uniaxial superparamagnetic nanoparticles

Mrabti

Titov

Déjardin

et al. 2011

Journal of Applied Physics

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Articles you may be interested inSuperparamagnetic nanoparticle detection using second harmonic of magnetization response Rev. Sci. Instrum. 84, 094702 (2013); 10.1063/1.4820447Magnetic anisotropy determination and magnetic hyperthermia properties of small Fe nanoparticles in the superparamagnetic regimeThe nonlinear stationary ac response of the magnetization of assemblies consisting of (i) noninteracting uniaxial superparamagnetic nanoparticles with aligned easy axes and (ii) randomly oriented nanoparticles subjected to superimposed ac and dc bias magnetic fields of arbitrary strength and orientation is calculated by averaging Gilbert's equation augmented by a random field. The magnetization dynamics of uniaxial particles driven by a strong ac field applied at an angle to the easy axis of the particle (so that the axial symmetry is broken) alters drastically leading to new nonlinear effects due to coupling of the thermally activated magnetization reversal mode with the precessional modes via the driving ac field. In particular, the high frequency response reveals significant nonlinear effects in the precessional motion with significant consequences for the dynamic hysteresis and ultra-fast switching of the magnetization following an ultrafast change in the applied field.

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Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

Coffey

Kalmykov

2012

Journal of Applied Physics

232

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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Dependence of prefactor on the angle between an applied field and the easy axis for single-domain particles

Cited by 7 publications

References 9 publications

Magnetization reversal time of magnetic nanoparticles at very low damping

Magnetization reversal time of magnetic nanoparticles at very low damping

Nonlinear stationary ac response of the magnetization of uniaxial superparamagnetic nanoparticles

Thermal fluctuations of magnetic nanoparticles: Fifty years after Brown

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