Effect of a dc bias magnetic field on the magnetization relaxation of antiferromagnetic nanoparticles

Abstract

The relaxation of the magnetization of antiferromagnetic nanoparticles owing to thermal agitation is treated via the Fokker-Planck equation describing the evolution of the distribution function of the magnetization orientations of an individual nanoparticle. By solving this equation using matrix-continued fractions, the correlation function of the longitudinal component of the magnetization, its characteristic relaxation times, and dynamic susceptibility are calculated for arbitrary dc field orientations across wide ranges of frequencies, temperatures, and damping. Furthermore, a simple analytic equation for the dynamic susceptibility at low frequencies is also proposed. It is shown that a dc field applied at an angle to the easy axis of the particle alters essentially the magnetization dynamics of the particle owing to coupling of the magnetization reversal mode with the precessional modes.