Nanoscale mapping of internal magnetization dynamics reveals how disorder shapes heat generation in magnetic particle hyperthermia

TL;DR

This study combines experiments and simulations to map heat generation within magnetic nanoparticles at nanometer scale, revealing how microstructural disorder influences heat distribution and efficiency in hyperthermia treatments.

Contribution

It introduces a microstructural understanding of heat generation in magnetic particles, linking grain size and disorder to localized heating behavior, guiding design of improved hyperthermia agents.

Findings

Larger grains in nanoflower architectures increase heat output.

Smaller grains create a more distributed and extended heat release.

Microstructural disorder controls the spatio-temporal heat distribution.

Abstract

Magnetic particle hyperthermia relies on the efficient conversion of magnetic field energy into heat in biomedical applications, yet the microscopic mechanisms governing heat generation within individual particles remain poorly understood. In this study, AC magnetometry experiments are combined with dynamic micromagnetic simulations to connect microstructural features, magnetization dynamics, and macroscopic heat dissipation. Beyond macroscopic heating metrics, the heat generation is resolved at the intra-particle level, uncovering a heterogeneous landscape of localized ''hot spots'' with nanometer spatial and nanosecond temporal resolution. The results demonstrate that grain size acts as a key experimentally tunable parameter, balancing anisotropy disorder and pinning strength, thereby controlling both the magnitude and spatio-temporal distribution of heat release within the particle. In particular, nanoflower architectures composed by larger grains deliver larger heat generation, while the smaller grains offer a deeper intra-particle pinning landscape, which effectively redistributes the heat generation over extended time windows. Together, our results provide a mechanistic framework linking nanoparticle microstructure to magnetic heating and establish design principles for optimizing nanoflowers as magnetic hyperthermia transducers.