A feasibility analysis towards the simulation of hysteresis with spin-lattice dynamics

TL;DR

This paper demonstrates the use of spin-lattice dynamics simulations to model magnetic hysteresis, analyzing how various parameters influence the hysteresis loops and extending the analysis to different temperatures and nanoparticle configurations.

Contribution

It introduces a coupled Langevin equation approach for simulating hysteresis, incorporating lattice dynamics and defects, and compares results with classical models like Stoner-Wohlfarth.

Findings

Field frequency and damping significantly affect hysteresis loops.

Anisotropy magnitude and symmetry behave as expected.

Lattice dynamics influence magnetic behavior more at higher temperatures.

Abstract

We use spin-lattice dynamics simulations to study the possibility of modeling the magnetic hysteresis behavior of a ferromagnetic material. The temporal evolution of the magnetic and mechanical degrees of freedom is obtained through a set of two coupled Langevin equations. Hysteresis loops are calculated for different angles between the external field and the magnetocrystalline anisotropy axes. The influence of several relevant parameters is studied, including the field frequency, magnetic damping, magnetic anisotropy (magnitude and type), magnetic exchange, and system size. The role played by a moving lattice is also discussed. For a perfect bulk ferromagnetic system we find that, at low temperatures, the exchange and lattice dynamics barely affect the loops, while the field frequency and magnetic damping have a large effect on it. The influence of the anisotropy magnitude and symmetry are found to follow the expected behavior. We show that a careful choice of simulation parameters allows for an excellent agreement between the spin-lattice dynamics measurements and the paradigmatic Stoner-Wohlfarth model. Furthermore, we extend this analysis to intermediate and high temperatures for the perfect bulk system and for spherical nanoparticles, with and without defects, reaching values close to the Curie temperature. In this temperature range, we find that lattice dynamics has a greater role on the magnetic behavior, especially in the evolution of the defective samples. The present study opens the possibility for more accurate inclusion of lattice defects and thermal effects in hysteresis simulations