Hysteresis, transient oscillations, and nonhysteretic switching in resonantly modulated large-spin systems

TL;DR

This paper investigates the nonlinear dynamics of large-spin systems under resonant modulation, revealing unique symmetry-induced effects such as hysteresis-free switching and transient oscillations influenced by relaxation mechanisms.

Contribution

It introduces a modified Landau-Lifshitz model to accurately describe classical spin dynamics, highlighting the role of symmetry and relaxation in nonlinear behaviors.

Findings

Hysteresis-free abrupt switching between magnetization states

Transient vibrations at combined Larmor and anisotropy frequencies

Modification of the Landau-Lifshitz model for large-spin dynamics

Abstract

We study the classical dynamics of resonantly modulated large-spin systems in a strong magnetic field. We show that these systems have special symmetry. It leads to characteristic nonlinear effects. They include abrupt switching between magnetization branches with varying modulating field without hysteresis and a specific pattern of switching in the presence of multistability and hysteresis. Along with steady forced vibrations the transverse spin components can display transient vibrations at a combination of the Larmor frequency and a slower frequency determined by the anisotropy energy. The analysis is based on a microscopic theory that takes into account relaxation mechanisms important for single-molecule magnets and other large-spin systems. We find how the Landau-Lifshitz model should be modified in order to describe the classical spin dynamics. The occurrence of transient oscillations depends on the interrelation between the relaxation parameters.