Magnetization waves and transverse relaxation in a chain of classical magnetic moments

Abstract

The paper presents the results of numerical simulation of the dynamics of linear chains of classical magnetic moments with dipole interaction. The chains are exposed to a constant external magnetic field, they include different numbers of particles and are placed in non-equilibrium initial conditions. The structures of the total magnetization signals and their Fourier spectra, as well as maps of the local magnetization of the chains, are analyzed. An equation for magnetization dynamics in the continuum approximation has been obtained and qualitatively analyzed. It has been found that, at a small initial transverse polarization, regular oscillations with a narrow spectral peak arise in the system. The local magnetization pattern shows that a traveling wave regime develops in the chain. By contrast, when transverse polarization is high, a spin-spin relaxation occurs at the initial stage of the system’s evolution. It comes from the accumulation of a phase difference in particle precession due to the variations of the local field. Disturbance propagation along the chain slows downs, and the values of the phase difference of oscillations between individual points are maintained for a long time. Thus, the return of the system to its initial state becomes impossible; on the other hand, its thermalization also does not occur.