Tuning field amplitude to minimise heat-loss variability in magnetic hyperthermia

TL;DR

This study uses simulations to identify optimal magnetic field amplitudes that minimize heat-loss variability in magnetite nanoparticles, enhancing uniformity in magnetic hyperthermia treatments.

Contribution

It introduces a theoretical framework combining shape anisotropy and field effects to optimize heating uniformity in nanoparticle assemblies.

Findings

Optimal field amplitudes for minimal heat-loss dispersion identified

Heating heterogeneity minimized at moderate field strengths

Particle size and frequency influence the critical field position

Abstract

In this work, we theoretically investigate how shape-induced anisotropy dispersion and magnetic field amplitude jointly control both the magnitude and heterogeneity of heating in magnetite nanoparticle assemblies under AC magnetic fields. Using real time Landau-Lifshitz-Gilbert simulations with thermal fluctuations, and a macrospin model that includes both the intrinsic cubic magnetocrystalline anisotropy and a shape-induced uniaxial contribution, we analyze shape-polydisperse systems under clinically and technologically relevant field conditions. We show that for relatively large particles, around 25 to 30 nm, the relative dispersion of local (single-particle) losses exhibits a well-defined minimum at moderate field amplitudes (between 4 to 12 mT), hence identifying an optimal operating regime that minimizes heating heterogeneity while maintaining substantial power dissipation. The position of this critical field depends mainly on particle size and excitation frequency, and only weakly on shape dispersion, offering practical guidelines for improving heating uniformity in realistic MFH systems.