Conservation laws for interacting magnetic nanoparticles at finite temperature

TL;DR

This paper develops a comprehensive Langevin Dynamics model for interacting magnetic nanoparticles at finite temperature, capturing energy, momentum transfer, and validating conservation laws through numerical tests, with applications in analyzing nanoparticle collisions and hysteresis.

Contribution

It introduces a coupled Langevin Dynamics model that accounts for both magnetic and mechanical behaviors of nanoparticles, including energy and momentum transfer expressions, validated through numerical simulations.

Findings

All conserved quantities are accurately accounted for in simulations.

The energy transfer expressions help decompose non-equilibrium power loss.

The model effectively analyzes nanoparticle collisions and high-frequency hysteresis.

Abstract

We establish a general Langevin Dynamics model of interacting, single-domain magnetic nanoparticles in liquid suspension at finite temperature. The model couples the LLG equation for the moment dynamics with the mechanical rotation and translation of the particles. Within this model, we derive expressions for the instantaneous transfer of energy, linear and angular momentum between the particles and with the environment. We demonstrate by numerical tests that all conserved quantities are fully accounted for, thus validating the model and the transfer expressions. The energy transfer expressions derived here are also useful analysis tools to decompose the instantaneous, non-equilibrium power loss at each MNP into different loss channels. To demonstrate the model capabilities, we analyse simulations of MNP collisions and high-frequency hysteresis in terms of power and energy contributions.