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

S. I. Denisov, K. Sakmann, P. Talkner, and P. Hänggi
Phys. Rev. B 75, 184432 – Published 24 May 2007

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.

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  • Received 31 January 2007

DOI:https://doi.org/10.1103/PhysRevB.75.184432

©2007 American Physical Society

Authors & Affiliations

S. I. Denisov1,2, K. Sakmann1, P. Talkner1, and P. Hänggi1

  • 1Institut für Physik, Universität Augsburg, Universitätsstraße 1, D-86135 Augsburg, Germany
  • 2Sumy State University, 2 Rimsky-Korsakov Street, 40007 Sumy, Ukraine

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Issue

Vol. 75, Iss. 18 — 1 May 2007

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