Approaching the Physical Limits of Specific Absorption Rate for Synthetic Antiferromagnetic Nanodisks in Hyperthermia Applications

Abstract

Magnetic nanoparticle-based hyperthermia presents a promising approach to treating malignant solid tumors that are resistant to traditional therapies such as chemotherapy and radiation. Although superparamagnetic iron oxide nanoparticles (SPIONs) are approved for clinical use in recurrent glioblastoma, their therapeutic potential is limited by low saturation magnetization, superparamagnetic behavior, and broad particle size distribution. To address these limitations, synthetic antiferromagnetic disk particles (SAF-MDPs) have emerged as an alternative. However, SAF-MDPs face challenges with undesirable magnetic properties, such as hysteresis-free magnetization loops or excessively high coercive fields in particles with in-plane and perpendicular magnetization, respectively. In this study, we present a novel SAF-MDP design guided by micromagnetic modeling, featuring in-plane magnetization optimized through uniaxial anisotropy adjustments to prevent the spin-flop phenomenon and eliminate hysteresis-free loops along the hard axis. Additionally, we employ mechanofluidic modeling to evaluate the alignment behavior of SAF-MDPs under an applied alternating magnetic field (AMF). Our comprehensive approach combines micromagnetic and mechanofluidic modeling with advanced magnetic characterization techniques, including single-particle analysis via magnetic force microscopy. This strategy enables the development of SAF-MDPs that achieve heating efficiencies near the theoretical maximum, constrained only by biologically acceptable frequencies and amplitudes of the AMF. These findings pave the way for new hyperthermia-based cancer therapies.