Modeling magnetic nanoparticles: application to hyperthermia

Behbahani, Razyeh (2021) Modeling magnetic nanoparticles: application to hyperthermia. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Using the Landau-Lifshitz-Gilbert (LLG) equation in micromagnetic simulations, we model magnetic nanoparticles composed of nanorods for application in magnetic nanoparticle hyperthermia, a developing cancer treatment. We use a scaling approach based on the renormalization group (RG) to calculate magnetization-field hysteresis loops that are invariant with simulation cell size, with the objective of decreasing the simulation time at clinically relevant field parameters. In addition, we introduce a time scaling approach that involves the sweep rate of the oscillating external field and the damping constant α in the LLG equation, which allows for up to three orders of magnitude faster simulations. Equipped with the RG and time scaling tools, we explore a macrospin model in which a complex nanoparticle is represented by a single magnetization vector with appropriate effective magnetic parameters. To evaluate this model, we calculate loops for single particles and particles interacting in pairs, chains and triangles of three particles, and in a cluster of thirteen nanoparticles. Motivated by recent experimental studies that reported successful hyperthermia treatment in the absence of perceptible heating of tissue, we report on local hysteresis loops of individual nanoparticles within clusters, highlighting the role of magnetostatic interactions between nanoparticles in the complex heating and magnetization dynamics of groups of nanoparticles.

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