Rapidly driven nanoparticles: Mean first-passage times and relaxation of the magnetic moment

Abstract

We present an analytical method of calculating the mean first-passage times (MFPTs) for the magnetic moment of a uniaxial nanoparticle which is driven by a rapidly rotating, circularly polarized magnetic field and interacts with a heat bath. The method is based on the solution of the equation for the MFPT derived from the two-dimensional backward Fokker-Planck equation in the rotating frame. We solve these equations in the high-frequency limit and perform precise, numerical simulations which verify the analytical findings. The results are used for the description of the rates of escape from the metastable domains which in turn determine the magnetic relaxation dynamics. A main finding is that the presence of a rotating field can cause a drastic decrease of the relaxation time and a strong magnetization of the nanoparticle system. The resulting stationary magnetization along the direction of the easy axis is compared with the mean magnetization following from the stationary solution of the Fokker-Planck equation.

24 pages, 4 figures

References in corpus (5)

• Dynamical and thermal effects in nanoparticle systems driven by a rotating magnetic field
• Magnetization of nanoparticle systems in a rotating magnetic field
• Switching Time Statistics for Driven Neuron Models: Analytic Expressions versus Numerics
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• Energy dissipation of rigid dipoles in a viscous fluid under the action of a time-periodic field: the influence of thermal bath and dipole interaction
• Temperature effects on drift of suspended single-domain particles induced by the Magnus force
• Dissipation-induced rotation of suspended ferromagnetic nanoparticles
• Stochastic dynamics of planar magnetic moments in a three-dimensional environment