Magnetization dynamics in Landau–Lifshitz–Gilbert formulation. FMR experiment modeling

A ferromagnetic resonance (FMR) spectrum of carbon coated magnetic nanoparticles in a non-magnetic elastic matrix has been investigated. The experimental absorption data have been compared with analogous data obtained with the help of the stochastic Landau–Lifshitz equation for the magnetic moment of a ferromagnetic single-domain nanoparticle and stochastic equations describing rotational oscillations of the polymer region containing a magnetic nanoparticle. We have shown that if polymer matrix anisotropies are blocking the rotational freedom of the easy axes direction of the magnetic nanoparticles, additional resonance peaks can appear in the FMR spectrum which are satellite peaks accompanying the main resonance peak. This is another mechanism for the appearance of additional peaks in the FMR spectra besides the spin-waves exchange mode in nanoparticles or inter-particle dipolar interactions. The compound Poisson process has been used to model this effect of additional correlations introduced on the motion of the particle’s magnetic moment.