Relaxation of the magnetization in uniaxial single-domain ferromagnetic particles driven by a strong ac magnetic field

Abstract

The magnetization spectrum and reversal time of uniaxial single-domain ferromagnetic particles driven by an ac magnetic field of arbitrary strength applied along the easy axis are evaluated by solving the infinite hierarchy of recurrence equations for the Fourier components of the relaxation functions governing the frequency dependence of the magnetization. A simple analytic equation for the reversal time is also obtained via the mean first passage time method exhibiting pronounced nonlinear effects such as a rapid decrease in the reversal time as the strength of the ac field increases. For weak ac fields, the results agree with perturbation theory.

Harmonic phase angle as a concentration‐independent measure of nanoparticle dynamics

“…Exact solutions for the case of strong AC magnetic fields, Ն1, as are present in MPI have seen recent progress. 30 Fitting of dynamic magnetization simulations to experimental data requires the use of several additional variables not required for static models. Static models require a lognormal size distribution of the particle core size.…”

Spin Relaxation in Phase Space

“…We shall, in particular, demonstrate that our quantum results in the classical limit, S   , correspond with those of Ref. [165]. Moreover,…”

“…[164] for nonlinear dielectric relaxation behavior of polar molecules in a strong ac electric field and in Refs. [165,166] for the nonlinear magnetization relaxation of magnetic nanoparticles in superimposed ac and dc magnetic fields. The difference as usual is that for a finite spin number S the solution of the evolution equation is rendered as a finite sum of spherical harmonics in contrast to the classical case, where the solution of the evolution equation involves an infinite sum of them.…”

Effect of a dc magnetic field on the magnetization relaxation of uniaxial single-domain ferromagnetic particles driven by a strong ac magnetic field

“…Furthermore, an efficient numerical algorithm for the calculation of the nonlinear ac stationary response of uniaxial superparamagnetic nanoparticles has been proposed by Raikher and Stepanov [3,7], from which they have described nonlinear magnetic susceptibility [3], the nonlinear magnetic stochastic resonance [7,15] and nonlinear dynamic hysteresis [10,16]. Now, in recent papers [17,18], the nonlinear transient and ac stationary responses of superparamagnetic nanoparticles have also been treated using the matrix continued fraction technique developed in Ref. [13] for the solution of infinite hierarchies of multi-term recurrence equations.…”