Magnetic vortices as efficient nano heaters in magnetic nanoparticle hyperthermia

TL;DR

This study demonstrates that magnetic vortices in larger soft magnetic nanoparticles can serve as highly efficient nano-heaters in biomedical hyperthermia, outperforming superparamagnetic particles in heat generation.

Contribution

The paper introduces the use of magnetic vortex configurations in nanoparticles as a novel and more effective method for magnetic hyperthermia treatment.

Findings

Vortex magnetization reversal occurs at moderate magnetic field amplitudes.

Hysteresis loop area increases with frequency for vortex states.

Vortex nanoparticles can achieve heat generation rates around 1 kW/g at 1 MHz.

Abstract

Magnetic vortices existing in soft magnetic nanoparticles with sizes larger than the single-domain diameter can be efficient nano-heaters in biomedical applications. Using micromagnetic numerical simulation we prove that in the optimal range of particle diameters the magnetization reversal of the vortices in spherical iron and magnetite nanoparticles is possible for moderate amplitudes of external alternating magnetic field. In contrast to the case of superparamagnetic nanoparticles, for the vortex configuration the hysteresis loop area increases as a function of frequency. So that high values of the specific absorption rate, on the order of 1 kW/g, can be obtained at a frequency 1.0 MHz. Because the diameter D of a non single-domain particle is several times larger than the diameter d of a superparamagnetic particle, the volume of heat generation for the vortex turns out to be many times larger. This shows the advantage of vortex configurations for heat generation in alternating magnetic field in biomedical applications.