Landau-Lifshitz-Bloch equation for ferrimagnets with higher-order interaction

TL;DR

This paper develops a micromagnetic Landau-Lifshitz-Bloch equation for ferrimagnets incorporating higher-order interactions, enabling accurate modeling of magnetization dynamics and phase transitions at various temperatures.

Contribution

It introduces a novel mean field approximation-based formulation that accounts for complex interactions, including four-spin terms, in ferrimagnetic materials.

Findings

Model accurately predicts phase transitions in FeRh.

Includes ferromagnetic and antiferromagnetic phases.

Validated against experimental data.

Abstract

We present a micromagnetic formulation for modeling the magnetization dynamics and thermal equilibrium in ferrimagnetic materials at low and elevated temperatures. The formulation is based on a mean field approximation (MFA). In this formulation, the ferrimagnet is described micromagnetically by two coupled sublattices with corresponding interactions, including inter- and intra-sublattice micromagnetic exchange as well as four-spin interactions described as an inter-sublattice molecular field with a cubic dependence of the magnetization. The MFA is used to derive a Landau Lifshitz Bloch type equation for ferrimagnetic material, including cases with a ferromagnetic - antiferromagnetic phase transitions. For validation, the results obtained via the presented model are compared with recent experimental data for phase transitions in FeRh.